Answer / shridhar awasthi

The oil is used is mineral oil,synthetic oil(Chlorinated diphenyl/askarel) and silicon oil.The synthetic oil is used to reduse the risk of fire.it is heavier than water,non-oxidising and has higher dielectric strength than mineral oil.the synthetic oil contains PCB (polychlorinated benzyne)which is hazardous for human being and handling of this oil require great precaution,which is why this oil is banned in many countries.
Silicon oil offers nearly all the advantage of synthetic oil and does not contain PCB also but ten times cost than mineral oil.
Silicon oil is an option where the fire is also a criterion.

Mineral oil in good condition appears clear and transparent.
It degrades faster due to oxidation,so anti oxidant called inhibitors are mixed with the oil to prolong it's life.
Dielectric strength of treated oil should be 50KV

For a 6.6kV Motor it is recommended to do megger test with 500 V d.c and not more than 5kV d.c but the Hi voltage withstand test should be performed by 12kV AC. Why the dc voltage test should be limited but AC voltage withstand test could be with such a high voltage?

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Dear Sir / Madam, Actually we requied 64 A MCB, But i have 32 A MCB = 2 No's this two i have to make series connection and we usw any place? isit possible or not......

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