(a) What is meant by the “clock-hour number” of a three-phase transformer?  Explain the symbol of three-phase transformer with “Dy11” stands for.      

(b) Explain why Dy11 transformer cannot be operated in parallel with a Yd1 transformer.

(c) Briefly explain why a three-phase induction motor does not develop any torque at synchronous speed?

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a Clock hour number Phase displacement of a threephase transformer is expressed as the clock hour nu... View the full answer