Question

For two-phase AC servomotor, if the rotor’s resistance and reactance are respectively R and X, its length and diameter are respectively L and D then,

(a) X/R and L/D are both small

(b) X/R is large but L/D is small

(c) X/R is small but L/D is large

(d) X/R and L/D are both large

I got this question at a job interview.

Query is from Concepts of State, State Variables and State Model topic in section State Variable Analysis and Design of Control Systems

Answer 1

Correct answer is (c) X/R is small but L/D is large

Easy explanation: Small X/R gives linear speed torque characteristic. Large L/D gives less inertia and good acceleration characteristic.