Question

The disadvantage of the Ward Leonard control method is ___________

(a) High initial cost

(b) High maintenance cost

(c) Low efficiency at high loads

(d) High cost, high maintenance and low efficiency

I got this question during an internship interview.

This intriguing question comes from Ward Leonard Speed Control Method topic in section DC Motors of DC Machines

Answer 1

Right answer is (d) High cost, high maintenance and low efficiency

To explain I would say: Ward Leonard speed control method requires large number of building blocks like generators, motors. Thus, installing cost and maintenance cost of the whole unit is very high. Apart from cost, it gives low efficiency at very high loads.