Electrical Engineering ⇒ Topic : Polyphase Mercury-arc Rectrifier
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Sachin
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Polyphase Mercury-arc Rectrifier These may be
Note 1. Glass rectifiers, because of inherent mechanical weakness of glass, cannot be manufactured fc very large outputs. These are usually made into units capable of D.C. output of 500 A at 500 V (maximum continuous rating). Note 2. Steel rectifiers are mounted in a vacuum chamber of steel, are dismountable, continously evacuated and are water cooled. Because water-cooling is employed, hence the condensing chamber is much smaller than that of the glass bulb type rectifier. The arc operates in a large vacuum tank which is made out of a special quality of sheet iron that resists the action of mercury vapours and helps in maintenance of consistently g,00d vacuum. In between the condensing chamber and the vacuum tank is the anode plate which carries the Main anodes in the ring. Necessary high vacuum is maintained by a pumping system consisting of a mercury vapour diffusion pump backed by a rotary pump working under oil. Ignition and excitation of steel tank rectifiers is different from that of the glass-bulb type rectifiers. Such units have been constructed for as much as 16000 A at comparatively low voltages, 2500 kW at 3.3 kV and for voltages as high as 20 kV at 600 kW. Voltages up to 30 kV can be obtained only by derating the current | |
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