Major Electrical Equipment-feb08

MAJOR ELECTRICAL EQUIPMENT

The maximum total electrical load for the Pelletron facility is expected to be 1500 KVA. One of the major electrical loads at the facility comprises the electrical and electronic equipment associated with the accelerator itself, which does not exceeds 150 KVA at any time during its operation. A fraction of the total load, amounting to about 60 KVA is due to electrical lighting and other electro- mechanical service equipment in the building need about 300 KVA. Provision has been made for another 400 KVA, that would be needed for the LINAC Booster when it becomes operational. Accelerator Equipment The Accelerator equipment may be divided into following six main categories: (1) Control Electronics (2) Ion Source Supplies (3) Accelerator Tank Equipment (4) Accelerator Power supplies (5) Magnet Voltage Supplies (6) Electrical Equipment Control Electronics It consists of, mainly, CAMAC system, control computer and other Low voltage solid state electronic circuit associated with small beamline components such as double slits, Faraday cups, beam profile monitors etc. The control system is described in Chapter 7. These low voltage, low power circuits do not present any electrical hazard to personnel. Ion source Supplies These are usually low voltage, medium power or high voltage, low power regulated DC power supplies. The control is manual, via light-links and CAMAC system, either from a local console or, remotely from the main console in

the Control room. The Ion Source and its associated equipment are mounted in a cubical enclosure, called the ion source DECK, which is supported on about 1.0 meter high porcelein insulators. The I.S. Deck is operated at a high potential of 300 KV by connecting it to a HT power supply. The main power for the ion source supplies is brought to the I.S. Deck through an oil filled, isolation transformer with secondary winding insulated from primary and ground for 300 KV. Accelerator Tank Equipment The electrical equipment within the accelerator column consists of, mainly several AC generators, drive motors, high voltage power supplies and control electronics. Intercommunication with control computer and CAMAC system is via light-links kept in the centre terminal and dead sections. The low energy dead section contains an electron trap, an electrostatic quadrupole doublet, ion pump and light-links. The lower or high energy dead section also contains identical equipment except for a foil-stripper in place of the quadrupole. The centre terminal has a ion pump, an electrostatic quadrupole triplet, sublimation pump (for foil and gas stripper chamber) and a variable aperture-Faraday cup assembly. It also contains control electronics and lightlinks. An AC generator of 2.5 KVA capacity is provided in each of the dead sections to supply mains power at 208/115 V, 400 Hz to the power supplies and other electronics. The centre terminal has two such generators. A small 0.2 KVA generator is also provided in each of the twentyeight, 1 MV modules. These generators are houses in the hollow aluminium casting and are meant for supplying power to the heater plates within the accelerating tube. All the column generators are driven by a common, insulated

rotating shaft, which is coupled to a 15 H.P. drive motor placed at each end of the column. The accelerator tank also contains the charging system already described in chapter 1. The Pelletron accelerator has been equipped with two pellet charging chains, each being driven by a 30 cm dia sheave and a 7.5 HP motor on the bottom base plate of the tank. High voltage required for charging the chains is brought in through feedthroughs provided in the tank base from a dual, ± 50 KV, 0.1mA regulated power supply placed outside the tank. MAGNET POWER SUPPLY The power supplies for the various magnets are supplied by M/s Danfysic (Demark) and M/s Sorensen Inc. USA and are mainly of two types, viz. High power, high current supplies used to energies the Injector, Analysing and Switching magnets. 2. Medium power, low current supplies for the quadrupole triplets and the magnetic beam steerers. 1.

Both are regulated power supplies with a conventional circuit design utilizing a bank of series power transistors to control the load current, which is sensed by a resistive element and a feedback amplifier. The power supplies are manually controlled from either the front panel or the main console. The high current type supplies are water cooled and are protected against coolant failure by thermal or flow switches interlocked with the contactors supplying main power. Low current supplies are air cooled and are also protected by thermal elements. High Voltage Power Supplies High voltage, low current and low stored energy power supplies, operating at 5-15 KV and 0-0.1 mA, are used to energise the

electrostatic beam steerers and quadrupole triplets in the low energy beam line and accelerator column. These supplies are self contained, completely shielding unit with a circuit based on a 100 KHz oscillator and a Cockcroft-walton type rectifier cascade. The output voltage is regulated through a potential divider sensor and a feedback amplifier and it can be controlled via the CAMAC system. The supplies are protected against overvoltage and spark breakdowns. A series protective resistor is connected at the output to limit surge currents. Similarity, a bleeder resistor is connected across output terminals to discharge the output capacitors when the power supply is switched off. A 300 KV, 1 mA regulated power supply of similar of design is provided for the pre-accelerator. Electrical Rotary Equipment Several electrical motors of various capacities are in use at different locations in the Pelletron Accelerator system, e.g. (i) (ii) (iii)

drive motors inside the accelerator tank for the chains and the rotating shafts. Linear motor drives for the shorting rods and the corona probe. Drive motors for the compressor and the rotary vacuum pump in the gas handling system.

ILLUMINATION Electrical lighting is provided at an average illumination level of 250-300 lux at the floor level in the laboratories and about 100 Lux in the staircase and corridors. In certain areas such as the laboratory block, control room,etc, illumination by natural light is also provided by an adequate number of windows. However, in radiation shielded areas such as the tower and the beam halls it is not possible to provide any window and all lighting is electrical. In order to avoid total darkness in the latter areas during power failures about 30 percent of the lights are connected to the emergency power line. A minimum

illumination level of about 100 lux at the floor level is thus ensured during mains power failure. However, as an additional back-up, portable battery powered emergency lights have also been installed in all the important areas. Fluorescent tube light in industrial mountings with transluscent covers are used to provide uniform and diffused lighting.