Question

Ideal commutation can be shown graphically by _____________

(a) Straight line passing through origin

(b) Straight line not passing through origin but with +ve slope

(c) Straight line not passing through origin but with -ve slope

(d) Curve increasing towards +ve t axis

This question was posed to me in class test.

Asked question is from Commutation Process in chapter Commutation Process & Excitation Methods of DC Machines

Answer 1

Correct choice is (c) Straight line not passing through origin but with -ve slope

The explanation is: Ideal Commutation (also called straight-line commutation) is that in which the current of the commutating coils changes linearly from + Ic to – Ic in the commutation period. Thus, it will form a straight line with -ve slope.