Question

Which of the following will be useful to generate positive feedback?

(a) Increasing the field resistance

(b) Increasing the armature resistance

(c) Decreasing the armature resistance

(d) Changing the shaft direction

I got this question at a job interview.

My enquiry is from Characteristics of Self Excited Generator in chapter DC Generator of DC Machines

Answer 1

Right answer is (d) Changing the shaft direction

To elaborate: Negative feedback can be remedied simply by reversing the field connection to the armature or reversing the direction of rotation. For large dc generators with permanent connections and a fixed direction of rotation, the problem is overcome by temporarily exciting the field from a battery source.