Question

A 4-pole, 3-phase, 50 Hz induction motor has a voltage between slip-rings on open-circuit of 520 V. The star-connected rotor has a standstill reactance and resistance of 2.0 and 0.4 Ω per phase respectively. Determine:

the full-load torque if full-load speed is 1,425 r.p.m.

Answer 1

The full-load torque of the 4-pole, 3-phase, 50 Hz induction motor can be calculated using the given voltage and rotor resistance. Substitute the values and use the formulas to find the full-load torque.

Step-by-step explanation:

The full-load torque of an induction motor can be determined using the formula:

Torque = (3 * power) / (2 * π * speed)

Where:

• Power is the power input to the motor
• Speed is the full-load speed of the motor

In this case, we need to find the power input to the motor. We can calculate it using the formula:

Power = V12 / R1

Where:

• V1 is the voltage between the slip-rings on open-circuit
• R1 is the rotor resistance per phase

Substitute the given values for V1 and R1 into the formula and find the power. Then substitute the calculated power and the given full-load speed into the first formula to find the full-load torque.