Stabilizer Write Up.docx

NOTE ON VOLTAGE STABILISER1 In our day to day life we use several devices that run on electric supply like lights, fans, fridge, TV, Computers, iron boxes, heaters etc. Similarly, there are innumerable equipment that are being used in industries for productive purposes that require electricity. The electricity available in India through the public distribution systems like state & privately owned electric supply boards is supposed to have certain standard characteristics. For example, the voltage is supposed to be 220 volts and the frequency is supposed to be 50 Hertz. Unfortunately, due to load fluctuations, line disturbances, and improperly maintained transmission centers, the voltage keeps fluctuating. The voltage may be continuously less or more than the required 220 volts or for a brief period the voltage may drop or rise. Most of the equipment that run on electricity are designed to operate at 220 volts. Hence these equipment may malfunction or the components inside the equipment might fail in case of voltage fluctuations. This failure can occur immediately if the equipment are sensitive or slowly over a period of time in case of equipment that are rugged. However, the users can not afford to have breakdowns due to voltage fluctuations due to high equipment costs and criticality of applications. For example, we would not mind replacing a light bulb that has failed due to voltage fluctuation, but can we afford to replace a fridge or a TV that fails? Even getting these things repaired is very costly. Similarly, in Industrial applications repair of textile machinery or medical equipment can be very costly. Also, the productive operation comes to a standstill due to breakdown of critical equipment. The most commonly used device to overcome such problems is the Voltage Stabiliser. The stabiliser gets connected to the mains supply and the equipment gets connected to the stabiliser. If the voltage is normal then the stabiliser supplies it to the equipment and if it is not, then the stabiliser first regulates the voltage by converting the low or high voltage to normal voltage and then supplies it to the equipment. SCHEMATIC DIAGRAM OF A VOLTAGE STABILISER CONNECTION Wire Connection

Voltage stabiliser

Wire Connection

Equipment - PC, Fridge, TV, Textile machinery, Lathe machine, Medical Equipment etc

Mains supply

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Prepared by Dr. Gururaj Kidiyoor, Professor, TAPMI as the primer for the bid game

A NOTE ON SOME OF THE TECHNICAL FEATURES OF A VOLTAGE STABILISER 1. INPUT VOLTAGE RANGE This implies the range of voltage that a stabiliser can handle. For example, if the input range for the voltage stabiliser is 165 - 270 volts, it means that as long as the mains electric supply is between 165 to 270 volts, the stabiliser regulates it to around the desired 220 volts. In case the voltage drops below 165 volts, the stabiliser would supply a voltage, which is significantly lower than 220 volts and if the input is more than 270 volts, then the stabiliser would supply a voltage, which is significantly higher than 220 volts. Under such situations the entire purpose of having a voltage stabiliser is lost. The design constraints limit the input voltage range bandwidth. Only marginal changes are possible. The entire bandwidth can be either lowered or increased to few voltages. 2. CUT OFF FACILITY Since the input voltage range is a constraint, cut off facility is very important to prevent any bad power entering the equipment through the stabiliser. For example, for a stabilizer that can handle input voltage between 165 - 270 volts, the voltage stabiliser can be made to stop automatically if the input voltage falls below 165 volts or rises above 270 volts. This is called the cut off facility where the stabiliser stops supplying (bad) power to the equipment when the voltage is beyond it's input capacity range. 3. MANUAL START When a stabiliser is switched on, it starts accepting power from the mains but will not immediately supply power to the equipment. For this to happen it is necessary to press a button provided on the stabiliser front panel. This switch is called the manual start switch. Under a cut off situation, when the input voltage again comes back to the normal range this switch has to be pressed again 4. AUTOMATIC START It may be inconvenient to press the manual start button every time, when the stabiliser is switched on and when normalcy is restored after cut off. Hence automatic start feature is Offered as an option or comes by default. 5. LOAD This refers to the VA (Volt Ampere) requirement of the equipment connected to a stabiliser. For example, the VA rating required by a TV is about 85 VA, Computers is about 250 VA, Printer is about 150 VA. The rating of a stabiliser determines how much load it can take. For example, a PC and a printer (250 VA + 150 VA = 400 VA) can be connected to a 400 VA stabiliser. The sum total of VA ratings of all the equipment that can be connected to a stabiliser is called the

"LOAD" on the stabiliser. The capacity of a stabiliser means its load capacity. A 1 KVA stabiliser is capable of getting connected to an equipment load of 1000VA. Rating of a stabiliser = max load that can be connected. Margin of Safety = Rating minus Load (R - L ) Desirable : R - L = 10 % of the KVA rating 6. TRIPPING If on a 400 VA stabiliser, 2 PCs and a printer are connected, then the load on the stabiliser is 650 VA (250 VA + 250 VA + 150 VA = 650 VA). Loading 650 VA on a 400 VA stabiliser is called "overload". A good stabiliser stops working under overloads to prevent damage to its components. This facility is called "tripping". 7. OUTPUT VOLTAGE RANGE No stabiliser is capable of giving exactly 220 volts output (which is the input to the equipment connected) all the time. This is due to the fact that a stabiliser requires certain time to respond to input voltage fluctuations that can occur on a continuous basis. Hence the output range can be as high as 220 V +/- 10 % ( poor quality ) or as low as 220 V + / - 1%( very good quality.). These variations may be acceptable or not depending on the equipment connected and its own input handling capabilities. 8. OVERLOAD PROTECTION This is nothing but the facility of tripping during overloads. Please not that tripping facility is desirable and can be provided during overloading, inputs being low or high, outputs being low or high etc. 9. RESPONSE TIME This refers to how fast a stabiliser responds to voltage fluctuations. For example, assume that input supply is 190 volts and the stabiliser is regulating this to give an output of 220 volts. Now, say the input voltage suddenly jumps to 265 volts, and it takes the stabiliser 3 seconds to adjust itself and again give a regulated supply output of 220 volts. The change in input is 75 volts (265 190 volts) and the stabiliser has taken 3 seconds to adjust. This means that the voltage stabiliser's response has been 75 volts / 3 seconds = 25 volts per second. This is called the response time of a stabiliser. 10. SPIKE Unusually high voltage input to the stabiliser (more than 350 volts) for a brief micro second. It can harm the equipment due to response time delay. Some stabilisers have built in spike arrestors that protect the equipment from spikes. Otherwise a separate spike buster needs to be connected externally which will come in between the mains supply and the stabiliser.

Voltage stabilisers can be broadly classified into two categories 1. Domestic Voltage Stabilisers 2. Industrial Voltage Stabilisers

DOMESTIC VOLTAGE STABILISERS These are the ones that are used for household appliances like TV, Fridge etc. These are of low value priced between Rs.350 to Rs. 1500 and the technology is not very superior. The price depends on the VA rating of the stabiliser. The response time of such voltage stabilisers is rather poor and the facility of cut off may not be available. There are innumerable manufacturers of domestic voltage stabilisers. The technology is low and is saturated. In fact it has come down to cottage industry level. However there are some regional players who run their business professionally like V-Guard & UMS. These stabilisers are sold through retail outlets where equipment requiring such stabilisers are sold. (such as fridge, TV etc ). Since these find a place in living rooms and kitchens aesthetics has become a major consideration for buying. Consumers buy these during their purchase of a fridge or a TV, mainly because the retailer tells them to buy, not being aware of the product specifications or what it is supposed to do. INDUSTRIAL VOLTAGE STABILISERS These stabilisers are used for industrial applications. They are used with almost all equipments that require a regulated voltage supply like computers, photocopying machines, CNC lathe machines, textile machinery, printing machinery, packaging machinery, photo processing equipment etc. Depending on the load various VA ratings are available - from 500 VA to 100 KVA and more. The price of a 500 VA stabiliser could be around Rs.2000.00 and for a 100 KVA stabiliser it could be in lakhs. Three phase models are also available in this category. These are the ones which take an input electric supply of around 415 volts and regulate it to 415 volts. There are several industrial devices that require three phase supply and hence industrial voltage stabilisers are also designed for this. (A 220 volts supply is called single phase supply). The technology of all industrial products is superior to that of domestic models and, hence for a given rating they cost more than the domestic stabiliser. Since the application is critical, after sales service is very important to avoid machine downtimes. Industrial voltage stabilisers are sold directly as well as through channels. Since these are available in various ratings for different applications, such distribution arrangements make sense.

The lower rated models ranging from 500 VA to 5 KVA (all single phase) are typically used for computers, STD/XEROX booths, photocopying machines, dental chairs, ultrasound scanners etc. These models are typically sold by manufacturer's dealers. The fast-moving segment is the Computer/Xerox/STD area where a strong reseller channel also exits. Resellers buy from company dealers and sell it to end users. This is a high volume, low value business. The high end stabilisers, 5-15 KVA in single phase and all three phase models are mainly sold direct. However, some numbers are also sold by the dealers who operate in such segments and have technical competence to market these products. These units are sold for use with photo processing equipment, CNC lathe machines, printing machinery, textile machinery etc. The equipment down time is a major concern for such applications and hence a lot of emphasis is accorded to after sales service. The AMC concept is quite popular for such stabilisers. There are innumerable manufacturers of voltage stabilisers in India. Most of them manufacture lower rated models. However, the number of manufacturers of 3 phase stabilisers is also quite substantial. There is hardly any manufacturer with a national presence. Some of the companies do have national level reach through channels but as the distance from their main area increases, their dependency on the channels goes up. The market is highly competitive especially in the lower rated segment where price seems to be the only buying criteria. For the higher rated stabilisers, price plays an important role but quality, reliability, after sales service, additional features also are given due consideration. Other than the stabilisers, established firms also manufacture and market other related power products like, Constant Voltage Transformers (CVT), UPS, Load Managers and Isolation transformers. Some firms position themselves as a "power protection" or "energy management" companies rather than just a "voltage stabiliser" company. Some reputed firms which manufacture only voltage stabilisers, offer the entire gamut of stabilisers in domestic as well as industrial segments. Mass media advertisement is rarely used for industrial stabilisers. Small manufacturers use "classified" sections in newspapers and the larger players use small infrequent insertions and ads in trade magazines.