Test: Three-Phase Transformers - Electrical Engineering (EE) MCQ

The V-V connected transformer and D-D connected transformers have same phase displacement, so they only can be connected in parallel to each other.

Three single phase transformers and one single unit of three phase transformer will be same only. this is done to reduce the cost and spacing.

Star-delta will have lower voltage at delta end.

Delta connected winding handle line voltages so it needs more turns in the winding but thin wires.

 If one of the transformers is removed from the bank of only delta-delta, then it behaves with 58% power delivery.

 If the core is not ferromagnetic then the transformer will not operate at all so no humming sound.

Due to aligned magnetic dipoles in the material, the size will reduce by a small margin and vice versa while demagnetization.

 If the frequency is reduced, the core flux density increases, so the noise also will increase.

In a star connected transformer, closed path to generate 3rd harmonic is not there. So the emf shape will be peaky in nature.

 The phase current will be reduced by 1/1.73.