Electronics and Communication Engineering - Automatic Control Systems - Discussion

However, under specific conditions, such as when R/X is relatively small (i.e., the resistance is much smaller than the reactance), the speed curve can become approximately linear. When R/X is small, it means that the effect of resistance on the phase angle between current and voltage is minimal, and the phase angle is primarily determined by the reactance.

In such a case, the motor's speed may exhibit a more linear relationship with the applied voltage or frequency.
So, to achieve a linear speed curve in a two-phase AC servomotor, you would want to design the motor and its control system in such a way that the effect of rotor resistance (R) is relatively small compared to rotor reactance (X).

This typically involves selecting appropriate motor design parameters and control strategies to minimize the impact of resistance on the motor's performance.

So, both R/X << 1 and X/R >> 1 are correct, which is option B.