Question 127Electricity & Electronics - 1st Asst/Chief

The correct answer is C) low or zero voltage drop reading, while the other coils will have higher readings. When testing the rotor of a synchronous motor for short circuits, a low voltage source is applied across the rotor coils through the collector rings. If a coil is short-circuited, it will have a very low or zero voltage drop across it, as the short circuit effectively bypasses the coil. In contrast, the other (non-shorted) coils will have a higher voltage drop, as the current will flow through their resistance. This low or zero voltage drop is the indication of a short-circuited coil. The other options are incorrect because they do not accurately describe the expected behavior of a short-circuited coil in this test scenario.