Power Quality And Conditioners

Power Quality FAQs What is power quality? Power quality means different things to different people, but it is generally an all-encompassing term used to describe the consistency and desirable characteristics, or lack thereof, of electrical power from its generation, delivery and usage. In nearly all cases, power quality is synonymous with voltage quality. What are power quality problems? For most people, power quality problems are anything related with electric power that interferes with the proper operation of their electrical devices. There are numerous specific types of power quality problems, each with their own causes and effects. What causes poor power quality? The causes of poor power quality run the gamut from squirrels or hot summer days to the failure of equipment on the electric utility’s system. Some causes can be corrected or eliminated while many others are out of anyone’s control, at any price. Read more about the causes of poor power quality… What are the symptoms of poor power quality? The symptoms of poor power quality can be as subtle as motors that prematurely fail every few years or as obvious as equipment that shuts down or as catastrophic as burned out circuit boards. How do I fix a power quality problem? Solutions to power quality problems are dictated by 1) the cause of the problem and its effect, 2) to what extent the problem needs to be corrected, and 3) most importantly, the financial value of correcting the problem. There is no single solution to any power quality problem, but the first and most critical step is to understand the problem and it’s effects. Read more about correcting power quality… Isn’t the electric utility responsible to fix my power quality problems? Yes - as long as they, the utility, are the cause of the problem and it is within their capability to fix it. But, electric utilities are only required to provide power within a broad set of limits. No - the electric utility can’t and won’t take responsibility for problems that are outside of their control or are acts of nature, God, etc. The long and short of the matter is that most electric utilities deliver power as they are required to do: nothing more and nothing less. It is very easy to determine if a problem is the fault of utility, which it rarely is. The vast majority of the time, power quality problems arise due to situations and conditions downstream from the electric meter (where the utility's responsibility ends).

Green Power Quality Two issues involving electric power are escalating simultaneously: consuming and producing electric power in a more “green” fashion and the need for a better quality of power. Green power, as splashed over various headlines, has many meanings, but it typically relates to being more efficient in electricity usage and more environmentally friendly in its production. However, quality power or power quality is a much less publicized topic. Sensitive electronics now appear in everything from the toaster oven to the controls that manage the most sophisticated manufacturing processes. It is in the commercial and industrial areas that power quality is a serious problem. If a toaster oven does not work properly because the voltage is too high or low, one can probably still make toast, maybe not automatically. However, if a large ice cream production line shuts down for 30 minutes due to a drop in voltage lasting less than a second, the result might be tens of thousands of dollars in revenue melting away. While poor power quality might be nuisance to the average homeowner, it costs U.S. businesses billions of dollars in lost revenue every year. Many businesses with huge bottom line dollars at stake invest heavily to avoid the costs incurred when the quality of their power affects their operations. But, this is the point at which the concepts of green power and power quality can be at variance: some solutions for maintaining power quality may be very “non-green” by substantially increasing the consumption of electricity. Here is an typical example: A mid-size manufacturing facility averages 50 power quality events per year that can cause their production to stop. Each time production stops because of these events, it costs $10,000 in lost material, labor and profit. Two solutions with the same first cost are available to correct these power quality events, but neither will solve 100% of them. The solutions are: Solution A Average events corrected per year: 48 Efficiency: 85% Annual energy losses: $70,000 Solution B Average events corrected per year: 46 Efficiency: 99% Annual energy losses: $5,000 While Solution B is might not be quite as effective, it saves $65,000 per year in energy losses and $45,000 in total even with the two extra events taken into consideration. In many cases, the efficiency of power quality solutions is given little consideration and the enduser winds up solving one problem but creating another: better power quality but much higher energy consumption. Being “green” by reducing energy consumption in today’s marketplace is not only great for the corporate image, but for the bottom line. Careful selection of energy efficient power quality solutions can yield substantial financial and other benefits besides delivering the necessary quality of power.

Applications The Sag Fighter™ is a specific type of power conditioner used for protection against deep voltage sags: deep voltage drops typically lasting less than a few seconds. For those applications where it is unnecessary or too expensive to use a UPS, the Sag Fighter™ offers solid, reliable sag protection at a fraction of the cost. The Sag Fighter™ is used for deep voltage sag proection in: Three phase applications 60 or 50 Hz 20 to 1,500 kVA Any voltage up to 600V Any type of load or load power factor Some common Sag Fighter™ applications include: Industrial Automotive Food and beverage Machining/Finishing/Assembly Pharmaceutical Plastics Pulp & paper Semiconductor Power & Petrochemical Power Generation Oil/gas production Transmission & Distribution Commercial Broadcasting Datacenters Laboratories Offices Printing & graphics Medical Public Services Municipal Services Schools Security

Power Conditioning for Medical Applications Medical Imaging and Oncology Treatment Healthcare organizations invest millions of dollars in medical imaging and oncology equipment to offer state-of-the-art treatment because it’s important to the patient and the reputation of the healthcare providers. When power quality problems damage this equipment or cause it to malfunction, it can be more than a scheduling inconvenience it can be detrimental to the patients treatment. This is why medical imaging and oncology equipment OEMs require or recommend power conditioning. Medical imaging and oncology units often require high inrush currents that can damage the power conditioners that are supposed to protect them. Only a power conditioner designed for high overloads should be used in these applications. UPS products and many electronic voltage regulators may be substantially oversized to handle the inrush currents, but these units are still being overstressed every time the medical imaging or oncology unit operates. With so much riding on the reliability of medical imaging and oncology units, it only makes sense to use a power conditioner that is designed to handle the power characteristics of this type of equipment. Let us show you or your consulting engineer how to make sure your medical imaging and oncology application gets the most reliable power conditioner.

Power Conditioning for Power & Petrochem Applications Power Generation Power plants, like any other operation, need stable voltages to keep critical control systems operating. Nuisance trips and outages increase maintenance and cost millions in lost revenue. But, in-pant voltage levels can often be less than ideal, especially during high demand periods or emergency operating conditions. Power generating stations often employ UPS systems to protect critical controls and put a power conditioner on the UPS bypass to stabilize voltages when the UPS is offline. Electronic voltage regulators with high fault clearing capacity are rapidly replacing mechanical and ferroresonant type conditioners in new applications. UST has a complete line of high fault clearing/high overload capacity electronic voltage regulators for UPS bypass applications and for other voltage stabilizing needs in power plants. Oil & Gas Production and Distribution Power quality problems like voltage sags at a refining facility cannot only interrupt operations they can create serious safety and environmental problems. Refineries require so much power that protecting all but critical controls with UPS units is impractical if not impossible. Battery-free deep voltage sag protection can help solve this problem. Oil and gas rigs often have problems with controls and instruments because of the power anomalies created by the frequent starting and stopping of heavy electrical loads. An industrial power conditioner can help smooth things out for these sensitive loads. UST manufactures deep voltage sag protection and power conditioning products for large or small applications. A wide variety of enclosure options are available, including explosionproof for some units.

Power Conditioning for Public Services Applications Municipal Services Services like water supply, wastewater treatment, light rail, rapid transit and others can all benefit from power conditioning. Motors for pumps, fans, compressors, HVAC, etc. overheat and fail unexpectedly when voltage levels are too low, and the controls for these devices can fail in short order when the voltage is too high. The total costs to the community cannot be measured simply in maintenance dollars but in lost commerce and the health and welfare of the citizens. For example, ultraviolet systems used for drinking water disinfection can be sensitive to voltage levels and to deep, but very short duration, drops in voltage known as voltage sags. The problem with this is that the ultraviolet system may take 5 to 10 minutes to restart. A voltage regulator or voltage sag correction unit can minimize or eliminate this costly problem. UST manufactures power quality devices for ultraviolet disinfection systems and a broad range of other municipal services applications. Offices&Schools Today’s schools and offices have millions of dollars invested in electronic devices and technologies intended to save energy and increase productivity. Power quality problems can put these investments at risk in many ways such as: Failure to achieve expected efficiencies, Delayed or unreachable payback, Inability to achieve desired performance, etc. Schools and offices can benefit from the lessons learned by business and industry years ago: poor power quality directly impacts the bottom line. Power quality problems occur with warning and all electrical equipment can be vulnerable to their effects. Power conditioning protect investments in electrical equipment and energy saving systems.

Power Conditioning for Industrial Applications Machining/Finishing/Assembly Machining, finishing and assembly operations benefit greatly from automated process equipment. Productivity and quality can be substantially increased by automation, but this equipment frequently demands good power quality to deliver maximum operational efficiency. Voltage problems can cause random and/or chronic equipment malfunction, premature motor and circuit board failure, increase down time and generally reduce the benefits obtainable from this high cost investment. UST power conditioners can be applied for individual devices, larger branch circuits or complete facilities. All UST voltage regulators and power conditioners are designed for the most challenging loads types like motors and magnetics with high inrush and poor power factor requirements.

Automotive Industry Automotive OEMs and their tiered suppliers have evolved into highly automated industries to reduce costs, handle volume and improve quality. Few things are more expensive for this industry segment than the unexpected shutdown of a process line or the breakdown of critical equipment. Costs skyrocket because of scrap and overtime and relationships are potentially damaged. Voltage sags that cause a finished paint line to stop can create huge losses and delays. Fluctuating voltages can damage critical equipment that can take hours or days to repair. UST power conditioners and voltage regulators are made to keep operations and equipment running even when the power is problematic. End users have little control over the quality of their incoming power, but they can avoid the vast majority of power-related financial losses. UST power quality products can often help the automotive industry multi-million dollar losses with a payback in less than 6 months.

Food & Beverage Processing What could be worse than thousands of melting ice cream bars? How about a bakery oven fire and thousands of cookies turned to ash? Large batch and continuous processes in the food and beverage industry can be very sensitive to high or low voltage levels and voltage sags. A power quality problem lasting but a few hundredsth of a second can turn into hours of cleanup and down time. Many UST products are available in washdown-type stainless steel enclosures for applications on equipment such as food packaging and metal detectors. Pulp & Paper Pulp and paper facilities can face a number of power quality challenges not the least of which is being located in remote locations. Being at the end of a long distribution line often means seeing large swings in the incoming voltage level. This combined with the large in-plant electrical loads like motors that stop and start frequently, can lead to many types of operational problems like equipment malfunction or shut down and premature failure of motors and/or electronics. One of the more common applications in pulp & paper plants is the protection of an individual piece of equipment or operation that has a problem with rapidly fluctuating voltages. The large starting loads and challenging power found in industries like pulp & paper, foundries, mines and heavy steel fabrication require power conditioning designed to withstand the rigors of these environments. UST electronic power conditioners protect sensitive equipment even in the toughest electrical environments. High inrush currents or overloads and poor power factor are no problem. Pharmaceutical In the pharmaceutical and many industries, power quality means more than simply avoiding equipment malfunction or damage: it means voltage stability or the absence of large voltage swings. Many devices depend on a stable voltage to operate with consistency and repeatability. Equipment like heaters, sterilizers and sealers, for example, depend on a certain voltage level to do their job by delivering heat at a constant temperature. The heat delivered depends on having a consistent voltage. The performance of other types of equipment can also be voltage dependent. This is where a voltage regulation becomes so important.

Power conditioner A DC power conditioner (also known as a line conditioner or power line conditioner) is a device intended to improve the “quality” of the power that is delivered to electrical load equipment. The terms “power conditioning” and “power conditioner” are misnomers. It is voltage rather than electric power that is being acted upon, and “conditioning” is actually the control and adjustment of voltage. Power conditioners can vary greatly in specific functionality and size, with both parameters generally determined by the application. Some power conditioners provide only minimal voltage regulation while others provide protection from half a dozen or more power quality problems. Units may be small enough to mount on a printed circuit board or big enough to protect a large factory. Small power conditioners are rated in volt-amps (VA) while larger units are rated in kilo-volt-amps (kVA). While no single power conditioner can correct all power quality problems, many can correct a variety of them. It is common to find audio power conditioners that only include an electronic filter and a surge protector with no voltage regulating capability. Industrial-Grade Power Conditioners & Voltage Regulators Quality Power. Better Business A power conditioner or automatic voltage regulator (AVR) can correct power quality problems, like brownouts, surges, over-voltage, sags, voltage imbalance, unbalanced current, line noise and others issues that cost business billions of dollars each year. Automatic voltage regulators and power conditioners from UST can correct these power quality problems and help you improve that all-important bottom line. Industrial-Grade Power Conditioning All UST power conditioners are rated industrial-grade which not only permits them to be used in the toughest applications but adds that extra measure of confidence in any application. Compared to computer-grade products, industrial-grade products feature: Sizing and installation like a dry-type transformer Compatibility with all load types Overload and fault clearing capability like a transformer “Short circuit-proof” and fan-free design True high efficiency – not subject to load or application variations No de-rating or limitations for low load power factor Operation without minimum load limitations An output free from added harmonics A load-maintaining automatic failsafe bypass No scheduled maintenance

What Do You Need? UST manufactures the largest and broadest range of electronic voltage regulators and power conditioners available. Automatic voltage regulator and power conditioner models are available in 1 and 3 phase configurations of for 50 or 60 Hz in sizes from 2 to 2,000+ kVA: 3 Phase Automatic Voltage Regulators and Power Conditioners Three phase automatic voltage regulators (AVRs) – the Sure-Volt™ power conditioner for a broad range of power quality problems in sizes from 5 to 2,000+ kV 1 Phase Automatic Voltage Regulators and Power Conditioner Single phase automatic voltage regulators (AVRs) – the Sure-Volt™ power conditioner for a broad range of power quality problems in sizes from 5 to 150+ kVA Single phase automatic voltage regulators (AVRs) – the Mini-EVR™ automatic voltage regulator in sizes from 2 to 15 kV 3 Phase Active Voltage Conditioners for Deep Voltage Sag Protectio Three phase active voltage conditioners (AVCs) – the Sag Fighter™ power conditioner for correction of deep voltage sags in sizes from 10 to 2,000+ kVA

Power Quality Problems There are numerous types of power quality issues and power problems each of which might have varying and diverse causes. To further compound the matter, it is all too common that different power quality problems can occur simultaneously, interchangeably or randomly. The following is a brief summary of typical power problems. Frequency Harmonics Sag (Dip)

Interruption (Blackout) Noise Notching Overvoltage(Swell)

Short Circuit Transient (Surge) Undervoltage (Brownout)

Interruption (Blackout) When the voltage drops below 10% of its nominal value it is called an interruption or a blackout. Interruptions have three classifications: momentary (lasting 30 cycles to 3 seconds), temporary (lasting 3 seconds to 1 minute) and sustained (lasting more than 1 minute). Although interruptions are the most severe form of power problem, they are also the least likely to occur. Voltage sags are often mistaken for an interruption because equipment shuts down or lighting goes off since the voltage dropped below the point that these devices can operate. Where sags and undervoltage typically represent more than 92% of power problem events, interruptions represent less than 4% of such problems. Undervoltage(Brownout) Undervoltage is a decrease in voltage below 90% of its nominal value for more than one minute. Undervoltage is sometimes called a "brownout" although this term is not officially defined. Brownout is often used when the utility intentionally reduces system voltage to accommodate high demand or other problems. The symptoms of undervoltage can range from none to daily equipment malfunction or premature equipment failure. Undervoltage may go unnoticed until new equipment is installed or the electrical system is otherwise changed and the new combined load depresses (see Sags) the voltage to a point where symptoms become apparent. Besides the obvious malfunction of equipment, chronic undervoltage can cause excess wear on certain devices like motors as they will tend to run overly hot if the voltage is low. Undervoltage is generally a chronic problem aggravated by a number of factors beyond the end user's control. Electric utilities try to maintain voltage levels delivered to customers at ±5%. However, factors like weather, high demand and others can cause the utility voltage to fall within a ±10% range. Even under ideal conditions, most customers will see a drop in utility voltage levels over the course of the day as demand begins to increase around 8 AM and peaks around 3 or 4 PM.

Distribution system characteristics can also contribute to chronically low voltage situations. For example, customers at the end of a long line may be subject to a permanent voltage drop due to line losses on top of the utility voltage variations. Sag or Dip The American "sag" and the British "dip" are both names for a decrease in voltage to between 10 and 90% of nominal voltage for one-half cycle to one minute Sags account for the vast majority of power problems experienced by end users. They can be generated both internally and externally from an end users facility. External causes of sags primarily come from the utility transmission and distribution network. Sags coming from the utility have a variety of cause including lightning, animal and human activity, and normal and abnormal utility equipment operation. Sags generated on the transmission or distribution system can travel hundreds of miles thereby affecting thousands of customers during a single event. Sometimes externally caused sags can be generated by other customers nearby. The starting of large electrical loads or switching off shunt capacitor banks can generate a sag large enough to affect a local area. If the end user is already subject to chronic undervoltage, then even a relatively small amplitude sag can have detrimental effects. Sags caused internally to an end user's facility are typically generated by the starting of large electrical loads such as motors or magnets. The large inrush of current required to starts these types of loads depresses the voltage level available to other equipment that share the same electrical system. As with externally caused sags, ones generated internally will be magnified by chronic undervoltage. Noise Noise is a high frequency distortion of the voltage waveform. Caused by disturbances on the utility system or by equipment such as welders, switchgear and transmitters, noise can frequently go unnoticed. Frequent or high levels of noise can cause equipment malfunction, overheating and premature wear. Frequency The U.S. electrical grid operates at 60 Hertz or 60 cycles per second. Because of, literally, the "mass" of the U.S. electrical system, it is very unlikely to encounter frequency problems. Virtually all electrical devices are capable of operating properly at frequency variations much larger those that could be seen in the U.S. The concept of very stable frequency does not apply to closed systems where electricity is generated on-site. Even large diesel-generator sets can have frequency problems. Also see Operating Frequency.

Harmonic Harmonics are a recurring distortion of the waveform that can be caused by various devices including variable frequency drives, non-linear power supplies and electronic ballasts. Certain types of power conditioners like ferroresonant or constant voltage (CVT) transformers can add significant harmonic distortion to the waveform. Waveform distortion can also be an issue with uninterruptible power supplies (UPS) and other inverter-based power conditioners. The UPS does not actually add distortion, but because the UPS digitally synthesizes a waveform, that waveform may be square or jagged rather than a smooth sine wave. Symptoms of harmonic distortion include overheating and equipment operational problems

Notching Notching is a disturbance of opposite polarity to the normal voltage waveform (which is subtracted from the normal waveform) lasting for less than one-half cycle. Notching is frequently caused by malfunctioning electronic switches or power conditioners. While it is generally not a major problem, notching can cause equipment, especially electronics, to operate improperly. Swell A swell is the opposite of a sag - an increase in voltage above 110% of nominal for one-half cycle to one minute. Although swells occur infrequently when compared to sags, they can cause equipment malfunction and premature wear. Swells can be caused by shutting off loads or switching capacitor banks on. Short Circuit A short circuit (or "short") is not normally considered a quality problem as much as it is a dangerous operational malfunction or fault. Short circuit refers to a condition where two "hot" lines are connected directly (or through a small impedance) or one "hot" line is connected directly to ground. A short circuit causes very high fault currents to flow through the wiring and all devices between the point of the short and the incoming power line. Left unchecked, a short circuit can very quickly lead to catastrophic overheating, melting and burning of wiring and devices. The opening of a breaker or the operation of a protective fuse is the normal means of guarding against damage from shorts circuits. It is imperative that protective breakers and fuses be of the proper size and characteristics to avoid the dangers of short circuits. Also see Fault Clearing.

Transients Transients are very short duration (sub-cycle) events of varying amplitude. Often referred to as "surges", transients are probably most frequently visualized as the tens of thousands of volts from a lighting strike that destroys any electrical device in its path. Transients can be caused by equipment operation or failure or by weather phenomena like lightning. Even relatively low voltage transients can cause damage to electrical components if the occur with any frequency. A properly sized industrial-grade surge suppressor is usually ample protection from the damaging effects of high voltage transients.

Power Conditioning Technologies There are many products offered to address power quality problems. Some devices such as the surge arrestor are very good at providing protection against a specific problem, while devices like power conditioners can provide protection from a wide variety of problems. The following is intended to provide a brief overview of many of the most common products used for power quality protection. Autotransformer Battery (Backup) Buck-Boost Transformer Constant Voltage Transformer (CVT) Electronic Tap Changer Ferroresonant Transformer Harmonic Filtering Inverter Isolation Transformer

Line Conditioner Line Isolation Mechanical Tap Changer Off-Load Tap Changer On-Load/On-Line Tap Changer Power Conditioner Primary Rectifier Secondary Sag Ride-Through

Surge Arrestor (Suppressor) Tap Changing Taps TVSS Uninterruptible Power Supply - UPS Voltage Regulation Voltage Regulator Voltage Stabilizer

Autotransformer Autotransformers, unlike an isolation transformer, have the primary and secondary coils built on a common core and offer virtually nothing in terms of power conditioning unless they integrated into a voltage regulator or power conditioner. They are an inexpensive means to change one voltage into another (e.g. convert 208V to 120V). Battery (Backup) A battery is an energy storage device. The heart of the UPS is its battery or batteries. Batteries are of the dry-type (sealed) lead acid batteries and wet-type (open) lead acid or nickel-cadmium batteries. All batteries have a finite life (discharge/recharge cycles) that are analogous to a loaf of bread. The loaf can be cut into many thin slices (moderate discharge) or fewer, thicker slices (deep discharge). Batteries in power conditioning devices provide electrical backup in the event of an interruption, however they come with a relatively high cost, limited correction time capacity and short life. Buck-Boost Transformer Typically a small, dry-type transformer with a dual voltage primary and a dual voltage secondary. Output voltage can be bucked (decreased) or boosted (increased) by by 5 to 20% by de-energizing the system and manually changing the internal wiring to the unit. These units are good for adjusting output voltage levels when the input voltage remains fairly constant. Having no automatic voltage adjustment capabilities, buck-boost transformers offer no capability to correct power quality problems, other than seasonal voltage fluctuations. Constant Voltage Transformer (CVT) - See Ferroresonant Transformer

Electronic Tap Changer Also known as electronic tap switchers, electronic tap changers have all of the taps of an isolation or autotransformer connected to the output through SCRs (Silicon Controlled Rectifier) that act as switches so that only one tap is connected to the output at any given time. Incoming voltage sensors feed information to a microprocessor that controls the SCRs to control the output voltage. Also known as electronic voltage regulators or power conditioners, these units offer very fast voltage correction because they have no moving parts and can jump from one tap to any other tap non-sequentially. Because of the SCRs and the electronic controls, these units some versions of these units may have limitations on overload capacity and power factor. Ferroresonant Transformer The "ferro" or CVT works by having a portion of its core in a saturated condition. Transformers create a magnetic field, or flux, that is function of the voltage applied. To a large extent, the magnetic flux is more or less proportional to the voltage except at the high or low voltage extremes. At these extremes, a relatively large change in voltage will result in little change in the magnetic flux, with the high voltage extreme described as being the "saturation" region. An analogy would be that of having a very large tank of water with a small outlet pipe at the bottom. As the water flow into the tank changes, the the flow of water out of the small pipe remains fairly constant due to the large volume of water in the tank. The majority of ferros are used in applications below 1.5 kVA, although there are models up to 25 kVA. Ferros can provide good noise attenuation and are very reliable. On the downside, ferros can add significant harmonic distortion, have a serious problem with high inrush currents (>170%), have very poor efficiency at less than full load and tend to be very hot and noisy in operation. Harmonic Filtering Harmonic filtering is removal of harmonics from incoming power. Passive filters are designed (tuned) to remove harmonics of specific frequency and amplitude but will provide little protection if the harmonic's characteristics change. Active filters (compensators) analyze the incoming power for deviations from the desired waveform. When a harmonic is detected, the unit superimposes a signal upon the waveform that is the opposite of the harmonic which then cancels out the harmonic. Passive filters are relatively inexpensive but have limited use. Active filters are expensive and are used in special circumstances where harmonics have become a problem. In most cases, harmonics are reduced to tolerable levels through isolation transformers or other power conditioning devices. Inverter A device that converts DC power to AC power. A basic component of the UPS and some other power conditioners. In and of itself, an inverter has no power conditioning capability. Isolation Transformer A transformer wound such that each winding is electrically isolated from the other windings, e.g., current will not pass from one winding to the other winding by conduction. This isolation serves to reduce minor transients and noise in the input from being transmitted to the output. Isolation transformers are often fitted with shielding between the primary and secondary to

further suppress noise and transients. These units are primarily used to step up or step down voltage and offer some protection from noise but little else in the way of power conditioning. Line Conditioner The term "line conditioner" is most commonly used to refer to a voltage regulator or power conditioner used in audio, video, graphics and computer applications. While a line conditioner typically serves the same purpose as a power conditioner, they tend to be for application at relatively smaller KVA ratings. Line Isolation Isolation between the primary and secondary sides of an isolation transformer. Mechanical Tap Changer Mechanical tap changers use a motor to drive mechanical components to change taps or otherwise alter the turns ratio. Generally, the motor moves a set of brushes or contactors from one position to another to physically engage each tap. Mechanical tap changers can achieve very precise output voltage regulation (<1%) and are relatively inexpensive. On the other hand, these types of units are very slow in making large voltage corrections because due to mechanical limitations and the necessity of changing taps sequentially. Modern electronic devices tend to require correction times that are much shorter than those that can provided by mechanical tap changers. Power Conditioner The term "power conditioner" in common usage refers to a voltage regulator that has capabilities other then simple voltage regulation. Frequently, power conditioners also provide varying degrees of line isolation, noise attenuation, surge suppression, harmonic filtering, phase balancing, etc. Primary/Secondary Primary refers to the input of a transformer and secondary refers to the output. Rectifier A device that converts AC power to DC power. A basic component of the UPS and some other power conditioners. In and of itself, a rectifier has no power conditioning capability. Sag Ride-Through Sag ride-through products are devices designed to counteract (ride-through) electrical sags. Technologies to accomplish this can be divided into the energy storage type and the non-energy storage type. The energy storage type devices store energy electrically or mechanically and discharge this energy to boost or completely augment the voltage when a sag occurs. These types of devices store energy in capacitors, batteries or rotating masses. These types of devices are expensive and have limitations on how long or frequently they can correct sags.

Non-energy storage type devices draw extra current from the system, even at extremely low voltages, to synthesize the voltage necessary to counteract a sag. These types of devices are substantially less expensive and some can provide sag correction without limitations on time or frequency of occurance. Surge Arrestor (Suppressor) Surge arrestors are generally metal oxide varistors (MOV) that clip (truncate) voltages above a predetermined threshold. Essentially a non-linear resistor, the surge arrestor is placed between a phase and ground. At normal voltage levels, the resistance of the surge arrestor is very high such that it negligible current flows to ground. At voltage levels above the threshold, the resistance of the surge arrestor becomes so low as to effectively create a short circuit, thereby diverting the damaging power of the surge to ground. Surge arrestors provide valuable protection against dangerous voltage levels. Tap Changing The process of changing taps on a transformer to adjust the output voltage. To change the taps in a typical transformer, the unit must be de-energized and isolated, the unit opened and the wiring or cable physically moved from one set of taps to another set of taps. The units are known as off-load tap changers. Units that can change taps while maintaining power to a load are known as on-load or on-line tap changers. Typically these are mechanical or electronic units. Taps The normal function of a transformer is to change an input voltage level to a different output voltage level, e.g., 480v to 208v. The voltage transformation ratio is determined by the numbers of "turns" on the primary and secondary sides of the transformer (turns ratio). Because the exact voltages in any given application can vary, transformers are frequently provided with "taps", that permit the turns ratio to be adjusted. A tap is simply an electrical connection to a transformer coil. By having taps above and below the nominal number of turns for a given coil, the turns ratio can be altered and the output voltage changed. With two 2.5% taps above and two below the nominal turns ratio, the output voltage can be adjusted by as much as ±5%. TVSS Transient Voltage Surge Suppressor. See Surge Arrestor. Uninterruptible Power Supply - UPS For small single phase applications, the uninterruptible power supply (UPS) is frequently the power conditioner of choice. The UPS can provide power conditioning as well as battery backup in the event of a power interruption. This permits time for ride through of the interruption or for the safe backup or shutdown of systems. The UPS has to be sized for the peak current required by the downstream devices and then for the length of time that full load current is required for system operation or shutdown. The physical size and cost of the UPS grow quickly as the size of the load and "battery time" increase. In large three phase applications, UPS can grow to room size units requiring sophisticated maintenance and monitoring systems to prolong the life of the batteries. Battery replacement in a UPS can be required in as few as 2 years, can run up to 65% of the initial cost of the unit, and depending on the battery type, can require special disposal of the old batteries.

UPS come in four basic versions: the standby (or off line), the line interactive, the ferroresonant and the double conversion. The standby UPS only offers protection in the event of a long sag or an interruption. In its normal mode, the battery and inverter of the standby UPS are off, and the downstream devices operate off of unconditioned line power. When a sag or interruption occurs, a mechanical switch turns on the UPS so that it can provide power to downstream devices. Once the event is cleared, the UPS goes back into its standby charge mode. Many standby UPS also incorporate surge protection. These types of units are most frequently used to protect individual devices like workstations. The line interactive works the same way as the standby UPS but adds the capability to provide some degree of voltage regulation (buck-boost) of the line power for the downstream devices. The ferroresonant UPS replaces the buck-boost portion of the line interactive UPS with a ferroresonant transformer to provide a higher degree of power conditioning of the line power for the downstream devices. The double conversion UPS provides the highest degree of power conditioning of any UPS. While the previous three types of UPS only utilize the batteries and inverter in the event of a sag or interruption, the double conversion UPS uses two inverters. This UPS takes incoming AC power, converts it to DC and then converts it back to AC power. In the event of a sag or interruption, the output inverter uses DC battery power to supply the load. The double conversion, with the backup provided by the batteries, can eliminate address many power quality problems, however this capability comes with a high first cost, operating cost and maintenance cost. Voltage Regulation One of the primary functions of voltage regulators and power conditioners is to maintain the voltage level seen by downstream devices within a certain set of limits. Typically, units will specify "input regulation" or "input range" and "output regulation". For example, one unit might have an input range of +10%/-25% and a regulation to ±5%. This means that if the incoming voltage is within the nominal voltage plus 10% and nominal voltage minus 25%, then the unit will regulate the voltage output to within the nominal voltage plus or minus 5%. If the nominal voltage is 480 volts, then as long as the input voltage is no higher than 528 volts and no lower than 360 volts, then the output voltage will be between 504 and 456 volts. Both input range and regulation will vary by manufacturer, technology and price range. Large input ranges and small regulation ranges tend to have higher price tags and vice versa. Most applications can be satisfied regulation of ±3 to 5%. Mechanical tap changing voltage regulators frequently offer output regulation in the range of ±1/2 to 1%, however these types of units have a significantly slower response time than other technologies. Voltage Regulator A voltage regulator, as the name implies, regulates voltage. Incoming voltage to the regulator is adjusted such that the output voltage level falls within a certain range. Voltage Stabilizer The the British equivalent of the Voltage Regulator

Applying a Voltage Regulator - Power Conditioner Critical Choices for Best Protection Applying a voltage regulator power conditioner is very simple in most situations. The following are some of the factors to be taken into account. As with any electrical product, care must be taken that all national, state and local codes are observed, that the specifying, installation, operation and maintenance of power conditioners is carried out by qualified individuals or licensed professionals. Application The first rule in applying a Voltage regulator power conditioner is: Place the power conditioner between the source of the power problem and the equipment to be protected. A corollary to this rule is: Placing the power conditioner immediately ahead of the equipment to be protected provides the maximum protection. The sources of power quality problems can be external or internal or both. External causes include undervoltage, sags, surges or other problems that are initiated on the electrical transmission or distribution network outside the end user's facility. The main electrical service entrance is the point of entry where these problems come into the facility. Internal causes tend to be sags and undervoltage created by large electrical loads or loads with high inrush current. Motors, magnets, transformers and welders are examples of internal loads that frequently cause power quality problems that can affect other equipment. A facility subject to chronic undervoltage because of its location in a large industrial park installs a new, CNC tool. When the new tool starts, the large inrush current depresses the already low voltage to the point that other equipment sporadically malfunctions. This is a typical example of external and internal conditions combining to cause a symptomatic power quality problem. To most effectively apply a power conditioner, there is no substitute for knowing as much as possible about the exact cause(s) of power quality problems. Following are some examples, good and bad, for applying a power conditioner. Legend The red lines indicate poor power delivery The green lines indicate protected power delivery The red and green lines indicate power delivery that can be intermittently good and poor.

Maximum Protection I This is the optimum application - a dedicated power conditioner in front of each device to be protected. In this scheme, each device is protected from external and internal sources of power quality problems. It also provides the highest degree of reliability because of the multiple units. The downside to this scheme is that it is also the most expensive. Larger units are less expensive (based on $/kVA) than multiple smaller units. Maximum Protection II Here again is the optimum application as loads (B) and (C) are protected from both external and internal power quality problems created by load (A). Protection from External Problems In this frequently used application, a power conditioner is sized to protect multiple loads from external power quality problems. Power conditioner costs are minimized by utilizing a larger single unit. If existing wiring is utilized, this can be the lowest cost application. The downside is lack of protection from internally generated power quality problems (see next example). This application is used where it is known that there are no large or problematic internal loads. Typical applications include installation at service entrances or ahead of distribution panels.

Unprotected from Internal Problems As in the preceding example, a power conditioner is sized to protect multiple loads, but in this case load (A) is a source of an internal power quality problem. Typically, this problem takes the form of a sag each time the load is started. This also serves to illustrate that, while the power conditioner is correcting for external problems, internal problems generated downstream of the power conditioner will go uncorrected. Loads (B) and (C) are protected from the external problems but are at risk from those generated by load (A).

Other Application Considerations Bypass In the context of voltage regulators and power conditioners a bypass may serve two purposes: 1) to divert power around a portion of the unit, or 2) to isolate the unit. When used in the first case to divert power around a portion of the unit, the bypass may be acting to protect the unit itself from extraordinary conditions or it may be providing power downstream because some portion of the unit is has malfunctioned or is temporarily inoperable. For example, if the batteries in a UPS have become drained to the point that they cannot provide power to the load, many UPS (if capable) may go into "bypass" thereby providing raw, unconditioned power to the load so it can remain on line. Also see Electronic Bypass. In the second case, generally for larger units, a bypass made up of circuit breakers or disconnect devices is provided so that both the incoming and outgoing "sides" of the power conditioner can be electrically isolated from system. In this situation, the unit can be safely isolated for maintenance purposes while the downstream devices receive unconditioned power to remain on line. Step Down - Step Up Some voltage regulators and power conditioners are capable of taking incoming power at one voltage level, 480 volts for example , and providing it at a lower voltage level, like 208 volts, at the output. This ability to "step down" the voltage can eliminate the need for a separate transformer to change the voltage to the proper level for the downstream devices. In some cases, a step up might also useful, and some manufacturers can provide this arrangement. Wiring Connections Single phase voltage regulators and power conditioners have simple input and output connections - generally, two "hot" lines in and two "hot" lines with a new ground coming out. In some cases, a single phase unit might be supplied with a line coming from an extra "tap" on the secondary in order to provide single phase output voltages at two convenient levels, such as 240v and 120v. This arrangement is sometimes referred to as a "split phase". Voltage regulators and power conditioners in three phase applications typically utilize a "delta" input and a "wye" output which is the most common arrangement in industrial and commercial applications. The "wye" output is particularly useful since it affords the possibility of having the output voltage at two different levels (line-to-line and line-to-neutral) and it provides a new ground reference for downstream devices.

Calculating kVA Sizes For single and three phase applications Calculating the size of a power conditioner is relatively straightforward. The most challenging aspect is usually the determination of the amperage (or current). Single-Phase Sizing 1. Determine input voltage for the equipment or circuit to be protected 2. Determine the rated amperage for the equipment or circuit to be protected 3. Multiply the voltage by the current and divide by 1,000 to obtain the size rating in kVA Example A single phase device has a nameplate rating of 120 volts, 40 amps The single-phase kVA size is then: 120 X 40 = 4,800 volt-amps 4,800 volt-amps ÷ 1,000 = 4.8 kilovolt-amps -- approximately 5 kVA Three-Phase Sizing 1. Determine input voltage for the equipment or circuit to be protected 2. Determine rated amperage for the protected equipment or circuit 3. Multiply the voltage by the current by 1.732 and divide by 1,000 to obtain the size rating in kVA Example A three phase device has a nameplate rating of 480 volts, 60 amps The three-phase kVA size is then: 480 X 60 X 1.732 = 49,882 volt-amps 49,882 volt-amps ÷ 1,000 = 49.9 kilovolt-amps -- approximately 50 kVA Amperage/ Inrush Current AC amperage is a measure of the flow of current to a device or in a circuit. Electrical devices will draw varying amounts of current depending on their operating state or the amount of work they are doing. For example, the current flow into a three phase electric motor goes from zero (off) to a peak level (peak, locked rotor, starting, or inrush current) and drops down to an intermediate level (full-load or steady state current). The starting current for a three phase motor can be 5 to 10 times that of the full-load current. Also see Overload Capacity. Amperage Calculation Determining the amperage to use in the KVA size calculation depends on the type of power conditioner to be used. For power conditioners with a high overload capacity, the steady state or

full-load amperage is typically used. For power conditioners with low tolerance to overload conditions the starting or peak amperage is typically used. As could be expected, it is not unusual for power conditioners with high tolerance to overload to be sized 20 to 50% smaller than their intolerant counterparts. There are several ways to determine these amperages. The first way would be to get the amperages from the nameplate or documentation for each device. This method tends to be fairly accurate and can often be accomplished fairly easily. A second way would be to determine the circuit breaker amperage rating for the circuits protected by the power conditioner. This method tends to give values that are too high for overload tolerant units and may be too low for the intolerant types. A third way is to measure the current for the devices or circuits to be protected. This method should only be undertaken by qualified technicians or professionals familiar with measurement method and safety procedures. This method can provide very good results as long as one can be certain that amperage measured accurately represents the expected maximum draw. In all cases, it is prudent to ensure that there is some amount of margin in the calculation of the amperage, not for the benefit of the power conditioner, but to ensure that the power conditioner is not undersized

Specifications Guide The specifications for power conditioners and voltage regulators can be confusing. The following summary of typical power conditioner terminology is oriented towards voltage regulators and sag ride-through devices, although many of the same terms are applicable to other technologies such as the uninterruptible power supply (UPS), dynamic voltage restorer (DVR), etc. Circuit Breaker Correction Duration Efficiency Electronic Bypass Fault Clearing Harmonic Distortion Impedance Independent Phase Regulation Input Range

Input Voltage KVA Line Isolation Load Load Power Factor Minimum Load Noise Attenuation Operating Frequency Output Regulation

Overload Capacity Phase Power Factor Limitation Response Time Ride Through Size Snubber Surge Suppression Technology

Circuit Breaker

This feature provides protection from short circuits and overcurrent for the power conditioner and equipment and wiring downstream of the power conditioner, regardless of events upstream from the power conditioner.

Correction Duration

Correction duration is the length of time that a power conditioner can continue to correct a power quality event. Power conditioners that rely on energy storage (e.g. capacitors, batteries, flywheels) as their primary means of conditioning may not be able to provide correction for events that last for more than a few cycles or seconds or if several severe events happen in rapid succession. Power conditioners that do not rely on energy storage of generally provide unlimited correction time.

Efficiency

Efficiency is simply the power coming out of a unit divided by the power going into a unit, usually expressed as a percentage.

All voltage regulators and power conditioners "consume" energy in the process of performing their task. Typically this consumption is in the form of losses that occur within the components (e.g. transformers) where the lost electrical energy is converted to mechanical energy in the form of heat or motion (vibrations). Efficiencies can run the spectrum from less than 50% to 99%. Most units will have efficiencies that are relatively constant across the load range, however ferroresonant transformer-based units tend to have efficiencies that fall off very quickly for points below full load. Efficiency may be one of the most overlooked parameters when selecting a voltage regulator or power conditioner. A quick gauge of the cost of differences in efficiency can be had by

multiplying the KVA size of the units by the difference in efficiency by 7. The result will be an approximation of the annual energy cost difference (at $0.08/KW-HR) in dollars. For example, for 25 KVA units with a 3% difference in efficiencies, the unit with the lower efficiency would cost about $525 more per year in extra energy consumption. Electronic Bypass

With many power conditioners, if a malfunction occurs, the power conditioner shuts off and the power for the load is lost. For mission critical and other applications, this is not an acceptable option. An electronic bypass allows the power conditioner to continue providing unregulated power to the load, even in the case of a component failure. Besides not dropping the load, the electronic bypass also protects the load in the event of a component failure in the power conditioner. For some types of power conditioners, a component failure or malfunction could result in potentially damaging output voltages being sent to the load.

Harmonic Distortion

This is the distortion of the voltage waveform by the power conditioner (making it appear jagged rather than smooth). The less distortion added the better. Voltage regulators that operate by switching taps (tap changing), particularly electronic voltage regulators, can cause a phenomena known as "notching". If the waveform is not at zero (the point where it crosses the horizontal axis) when the regulator changes taps, then the output voltage waveform will be distorted.

Impedance

Impedance is the opposition to the flow of electrons in an AC circuit as a function of the circuit's resistance, capacitance and inductance. Impedance in an AC circuit is analogous to resistance in a DC circuit. Even simple wire conductors have properties of resistance and inductance that affect the impedance of an AC circuit. High impedance can have a significant impact on power quality in that it directly affects voltage as a function of the current flow. For example, a device drawing 1A on a circuit with a 1 ohm impedance and a 100V source will see 99V. If that same device draws 10A, it would see only 90V. The same device on a circuit with a 0.1 ohm impedance would see 99.9 and 99V, when drawing 1 and 10A, respectively. A circuit or system with a low impedance is said to be "stiffer" than its high impedance counterpart because the voltage changes less as a function of the current.

Independent Phase Regulation

In three phase applications, the incoming voltage level of each phase is frequently unbalanced (e.g. Phase A = 440v, Phase B = 469v, Phase C = 453v). This unbalance can cause many electric devices, such as motors, to run inefficiently which, in turn, causes them to run at higher temperatures and wear out prematurely. Units that offer independent phase regulation provide much more accurate voltage regulation and a higher level of protection than units that assume that the phase voltages are balanced.

Input Range

Percent deviation above and below the nominal (or rated) input voltage that can be corrected to within the specified output regulation. In other words, this is a measure of how widely the input voltage can vary from what it is supposed to be. The larger the "spread", the better (e.g. +10% to -25% provides a wider input voltage window than ±10%). For a nominal 480v input voltage, an input range of +10% to -25% equals 528v to 360v.

Input Voltage

Standard input voltage offerings. Also see Step Down-Step Up

Size (kVA)

The kVA sizes available. See Calculating kVA Sizes

Line Isolation

Line isolation is the electrical separation of the incoming and outgoing power through an isolation transformer. These transformers reduce noise and transients that may be present in the incoming power. The efficiency of units using an isolation transformer will typically be 2 or 3 percentage points lower than units not providing line isolation.

Load

A device or collection of devices that draw energy from the electrical system is called a load. The load can be made up of active (motor, variable frequency drive, etc.) or passive (resistor, inductor, capacitor, etc.) components. Also see Power Factor.

Load Power Factor and Power Factor Limitation

Devices like transformers and motors require power to maintain magnetic fields to perform their function. This so called “reactive” (kVAR) power flows into and out of the device but is not really consumed to perform work. The power that is consumed is called the “real” (KW) power and the vector sum of reactive and real power is called the “apparent” (kVA) power. Power factor (PF) is the ratio of real power to apparent power. The terms “leading” and “lagging” refer to reactive power being put in or taken out by the device. In the real world, leading power factors are rare. For individual devices, lagging power factors can typically range from 0.4 to 0.99. With respect to power conditioners, a limitation on load power factor is generally required if the unit will not operate or respond properly if the power factor is too low. Unless the power factor of the existing or future devices to be protected are well known, it is best to select power conditioners with no (or minimal) load power factor limitations.

Noise Attenuation

Noise attenuation (reduction) is a common feature of power conditioners. Electrical noise reduction is measured in decibels (db). The db is a logarithmic ratio of intensity or, in the case of electrical noise, the amplitude of one noise voltage level to another. For example, a 40 db reduction in noise means that the incoming noise is reduce by a factor of 10,000. There are two types of reduced noise: common mode and normal mode.

Common mode noise exists between the ground and the neutral. Electronic devices are most sensitive to common mode noise. A shielded isolation transformer is very effective in reducing common mode noise. Normal (or transverse) mode noise exists between the "hot" lines and the neutral. Normal mode noise is generally also reduced with a shielded isolation transformer. Minimum Load

Power conditioners are frequently used to protect circuits with multiple loads. If the power conditioner requires a minimum load to operate properly, then care must be taken to coordinate the starting and stopping of individuals loads.

Operating Frequency

Voltage regulators and power conditioners come in either 50 or 60 Hertz (frequency) or in some smaller units dual frequency (both 50 and 60 Hz). The USA, Canada, Mexico, Puerto Rico, South Korea, Taiwan and the Philippines use 60 Hz. Europe, most of Asia and Africa and Australia use 50 Hz. Latin American and Caribbean countries are a mix of 50 and 60 Hz, depending on the country. Some countries such as Japan, Saudi Arabia and Brazil use both. In most developed countries, electric frequency deviates very little from the standard. A deviation one-half percent would be considered unusual. For this reason the operating frequency of the power conditioner is generally not an issue. In countries with very unstable electrical systems or when using a power conditioner behind a generator, frequency of operation can become an issue. Most power conditioners do not correct frequency. If frequency correction is required, it would normally be done separately ahead of the power conditioner.

Output Regulation

Percent deviation above or below the nominal (or rated) output voltage when the incoming voltage is within the input range. In other words, this is a measure of how accurate or tight the output voltage will be. Smaller numbers mean more precise regulation. An output regulation of ±3% is well within the tolerance required by the vast majority of electric devices. For special applications such as laboratory testing or calibration, an output regulation of ±1.5% or less may be more desirable. For a nominal 208v output, ±3% output regulation equals 214v to 202v. With many voltage regulators, there will be a direct correlation between the input range and the output regulation. As the output regulation becomes smaller, the input range will also shrink. This is due to the fact that manufacturers will have a fixed number of points or taps at which changes in output voltage can be made. To decrease the output regulation percentage without decreasing the input range requires that more taps be added. This becomes a custom and more expensive design.

Fault Clearing and Overload This is a measure of a unit’s ability to tolerate levels of current Capacity higher than the rated current without sustaining short or long term wear or damage. Many electric devices, like motors, magnets, transformers, etc., require a large inflow of current when started (inrush current). A "typical" AC motor has an inrush of 500 to 1000% of the normal current that peaks in a few cycles and then decays to normal levels within 10 to 30 cycles. Power conditioners with ratings like 1000% for 1 cycle might not be good choices for industrial or commercial applications with frequent or large inrush current. For this measurement, the higher the percentage and the longer the time at that percentage, the better the unit should stand up to high inrush applications. Fault clearing has a relationship with overload capacity in that both describe the ability of the power conditioner to operate for some period of time at current levels above the unit's rating. If a power conditioner cannot pass enough current without tripping or shutting down, downstream equipment and protective devices may not be able to "clear" or reset themselves, thus creating an annoying operational problem. Phase

Availability of single and three phase AC models

Load Power Factor and Power Factor Limitation

Devices like transformers and motors require power to maintain magnetic fields to perform their function. This so called “reactive” (kVAR) power flows into and out of the device but is not really consumed to perform work. The power that is consumed is called the “real” (KW) power and the vector sum of reactive and real power is called the “apparent” (kVA) power. Power factor (PF) is the ratio of real power to apparent power. The terms “leading” and “lagging” refer to reactive power being put in or taken out by the device. In the real world, leading power factors are rare. For individual devices, lagging power factors can typically range from 0.4 to 0.99. With respect to power conditioners, a limitation on load power factor is generally required if the unit will not operate or respond properly if the power factor is too low. Unless the power factor of the existing or future devices to be protected are well known, it is best to select power conditioners with no (or minimal) load power factor limitations.

Response Time

This is the time it takes the unit to respond to deviations in the incoming voltage. The shorter the time, the better the unit is at keeping the voltage within the output regulation range. There is another term, "correction time" that may also appear in specifications. This is the time that it takes for the unit to adjust the output voltage to within the output regulation range, once the unit has begun to respond. The total time it takes a unit to correct a low or high voltage situation is the response time plus the correction time.

Electronic voltage regulators are so fast, that response time and correction time are frequently used interchangeably. On the other hand, mechanical voltage regulators have a response time similar to that of the electronic units, but their slow correction time (measured in seconds) is really the limiting factor.

Ride Through

The term "Ride through" in general usage refers to the capability of a device to correct or withstand a certain type of power quality problem. Typically, ride through is used in conjunction with sags or interruptions. Also see Correction Duration.

Size (kVA)

The kVA sizes available. See Calculating kVA Sizes

Snubber

A snubber is a special type of filter that blocks high frequency, high voltage transients that would not typically be handled by other means in the power conditioner.

Surge Suppression

Surge suppression provides protection for the power conditioner and downstream equipment against large "surges" of voltage as can happen during system transient events such as lightning strikes or transmission/distribution equipment malfunction. Surge Suppression is often accomplished with metal oxide varistors (MOVs), zinc oxide, or surge capacitors.

Technology

Motorized variable transformer units use motors to physically move or re-orient hardware within the unit to regulate the output voltage. These units can offer very precise regulation and good overload capacity but have very slow response times and, as with all mechanical systems, require regular maintenance or service. Electronic tap changers offer good regulation, very fast response times and have no moving parts, but some (not all) units have very poor overload capacity.

Sag Fighter™ Operation The Sag Fighter™ is a series-connected, inverter-based, voltage compensation device with builtin surge suppression. The Sag Fighter™ consists of a three phase transformer with each of its secondary windings connected in series between the source (incoming line) and the load(s). Figure 1 shows a schematic of a single phase of the unit. Normally, the unit operates in a “bypass” mode with the primary of the transformer shorted electronically through SCR switches, so that load current flows through the secondary windings of the transformer. The ampere-turn balance is maintained through the primary SCR switches. The Sag Fighter™ continuously monitors the input voltage waveform for any deviation (user selectable) from a balanced, three phase supply voltage. Upon sensing such a deviation (as would normally be caused by a voltage sag), the Sag Fighter™ engages, within 1/8th of a cycle, an inverter circuit to apply a compensating voltage to the primary windings of the series connected transformer. The compensating voltage is synthesized with a magnitude, shape, and phase angle such that when it voltage is injected in series with the abnormal supply voltage, the resulting output voltage is a balanced, three phase voltage for the load(s). When a normal three phase supply voltage returns to the input of the Sag Fighter™, the inverter circuit is disengaged and the unit returns to its bypass mode. It is important to note that the Sag Fighter™ operates differently than traditional voltage regulators in that it does not provide continuous, fine correction. Typically, the trigger point for the Sag Fighter™ is set around 90% of nominal voltage. This means that the unit will only start providing correction once the voltage drops below 90% and it will then correct the voltage back to ±5% of the nominal voltage. Mini-EVR™ Operation The Mini-EVR™ works automatically with no operator effort required. There is no scheduled maintenance, so it is virtually effort-free. The standard Mini-EVR™ uses microprocessor-controlled tap switching technology like its big brother, the Sure-Volt™. Rather than an isolation transformer, the Mini-EVR™ uses an autotransformer to reduce size, weight and provide a 99% efficiency. Relative to a ferroresonant transformer, the Mini-EVR™: Requires no oversizing for inrush current Creates minimal load on air conditioning Has near-silent operation Can readily be installed in weatherproof or hazardous location enclosure Is less than half the weight Installation of the Mini-EVR™ is simple. It arrives completely assembled, ready to wall mount like a typical panel. The is no assembly, no programming, nothing to adjust, no training needed - essentially "plug and play". Sure-Volt™ Operation The Sure-Volt™ works automatically with no operator effort required. There is no scheduled maintenance, so the Sure-Volt™ is virtually effort-free. The standard Sure-Volt™ uses microprocessor-controlled tap switching technology with an isolated, shielded transformer. The unique design provides performance and reliability that are far beyond the ordinary electronic voltage regulator such as: Overload capacity - 60 times more Tap switching - no current interruption or transients Electronic switches - fully protected from high load currents Automatic failsafe bypass - keeps the load powered

Many electronic voltage regulators will have an overload capacity rating limited by their power semiconductors while some have current-limiting designs that can accept very high load currents without compromising the power semiconductors. It is possible to oversize electronic voltage regulators to get more overcurrent tolerance, but this may not guarantee that the power semiconductors are not overstressed in a high inrush/overload application. The better choice is to select an electronic voltage regulator with a high overload capacity. Mechanical Voltage Regulator Mechanical voltage regulators for power quality applications typically have very high overload capacities, however their use is limited and rapidly dwindling for a number of reasons: 1. Their correction speed is too slow to support electronic equipment, 2. They are often limited to smaller kVA ratings, and 3. Frequent voltage fluctuation results in high maintenance. In high inrush/overload applications where the voltage fluctuations are infrequent and correction speed is unimportant, mechanical voltage regulators might be a good choice. Uninterruptible Power Supply (UPS) The typical UPS has a low tolerance to high inrush/overload currents and is often substantially oversized to accommodate peak currents. Power semiconductors and/or ferroresonant transformers found in UPS units have the problems similar to those discussed above. When a high inrush/overload application is so critical that it demands the power interruption protection provided by a UPS, it is important to generously oversize the UPS for the peak current. Conclusion It is possible to use any type of power conditioner – voltage regulator in high inrush/overload applications, however some special considerations are needed if the power conditioner has limited overload capacity: 1. Determination of frequency of occurrence and magnitude of peak current loads, and 2. Sizing the power conditioner to avoid excessive stress on power semiconductors and/or keeping maximum currents below the critical limits for ferroresonant transformers. Electronic voltage regulators with high overload capacity and mechanical voltage regulators (where applicable) are the best choices for high inrush/overload applications since they eliminate the need for oversizing, provide higher reliability and are less likely to be affected by downstream faults. High overload capacity power conditioners are generally specified as accepting at least 1,000% of rated current for 60 cycles or more.