Question

A 8-kW, 4-pole, 220-V, 50-Hz reluctance motor has a torque angle of 30° when operating under rated load conditions. Calculate the load torque.
1. 51 Nm
2. 4.3 Nm
3. 43 Nm
4. 5.1 Nm

Answer 1

Correct Answer - Option 1 : 51 Nm

Concept:

A reluctance motor is a constant speed motor like a synchronous motor.

Speed (N_s) = 120 f / P

f = frequency, P = number of poles

Angular speed (ω) = (2 π N_s) / 60

Calculation:

Given

P = 4, f = 50 Hz, power = 8000 W

N_s = 120 × 50 / 4 = 1500 RPM

ω = (2 × π × 1500) / 60

ω = 157 rad/s

Torque = Power / ω

Torque = 8000 / 157

Torque = 51 N-m