Question

For the same rating machines, which of the following statement is correct regarding the efficiency (η)?

(a) η of low speed machine > η of high speed machine

(b) η of low speed machine < η of high speed machine

(c) η of low speed machine = η of high speed machine

(d) Any of the mentioned

This question was addressed to me in final exam.

My doubt is from Losses and Efficiency in portion Rating and Loss Dissipation of Electrical Machines

Answer 1

Right option is (b) η of low speed machine < η of high speed machine

For explanation I would say: The amount of conductor and iron materials required for a machine of given rating is inversely proportional to its speed. Also, more iron and conductor would entail more losses.