Question

In a $\Delta$–$Y$ transformer, the phase shift between primary and secondary is _______.

• A. 90$^\circ$
• B. 60$^\circ$
• C. 0$^\circ$
• D. 30$^\circ$

Hint:

$\Delta$–$Y$ and $Y$–$\Delta$ transformers have 30° phase shift between primary and secondary windings.

Answer 1

The Correct Option is D

Step 1: Understand transformer configuration
In $\Delta$–$Y$ or $Y$–$\Delta$ transformer connections, there is a phase shift introduced between primary and secondary line voltages.
Step 2: Phase relationship
For $\Delta$–$Y$ connection: \[ \text{Secondary line voltage leads primary by } 30^\circ \] Step 3: Practical implication
This 30$^\circ$ phase shift is essential when paralleling transformers — they must have same phase shift type to avoid circulating currents.