Question

Why field test is conducted even if Hopkinson’s test is present?

(a) Instability of an operation

(b) Possibility of run-away speed

(c) Both instability and possibility of run-away speed

(d) Field test is not conducted

I had been asked this question in examination.

This intriguing question comes from Hopkinson’s Test in chapter Efficiency and Testing of DC Machines

Answer 1

Correct answer is (c) Both instability and possibility of run-away speed

To explain: Regenerative test on two identical series motors is not feasible because of instability of such an operation and the possibility of run-away speed. Therefore, we have toconduct a loading test.