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RECTIFIER TRANSFORMERS

Transformers for AC/DC High Current Rectifier applications

Capacity up to 50 MVA;
DC Voltage up to 1000 V;
DC Current up to 140 kA;
AC Primary Voltage up to 145 kV;
Various configurations available in a single unit: single bridge, double bridge, double star with IPT, two double stars with IPTs;
Multi-pulse topologies available: from 12-pulse unit to 72-pulse;
Regulating autotransformer available in the same tank to allow on-load coarse voltage regulation;
Saturable reactors available in the same tank to allow on-load fine voltage regulation.

In conjunction with thyristor or diode rectifiers, these transformers form the link between the AC and the DC systems of the industrial plant.
Their development and construction requires extensive experience as well as deep theoretical knowledge.




ELECTROLYTIC PLANTS

We manufacture transformers for electrolytic plants. In this case both bridge and double star with interphase transformer circuits are frequently used. Coarse voltage regulation is often obtained by means of an on-load tap-changer (OLTC) operating on taps made on primary windings. We design the cooling system of a rectifier transformer with particular attention to the current harmonics arising from the rectifier operation, which can otherwise cause very high eddy current losses. This becomes very important in transformers for electrolytic plants and for SCR power circuits, where high values of delay angle determine very fast commutations. Rectifier transformers are usually oil-immersed, but dry-type units in sizes up to 5 MVA have been manufactured by our firm. In small oil immersed units natural cooling (ONAN) is utilized. In larger units cooling is mostly obtained by forced circulation of either oil and water (OFWF) or oil and air (OFAF) in a cooler connected by oil pipes to the transformer tank. The cooler acts as a heat exchanger with the heat flowing from either the oil to the water (OFWF) or the oil to the air (OFAF). In the case of OFWF cooling, two coolers are usually provided. Each of them is rated for the full transformer losses, so that the transformer can be kept running at its full load in the event of a failure of either a cooler itself or its auxiliary equipment.

METAL REFINING

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DC ARC FURNACE

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CHLORO-ALKALI

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PVC

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