AC Machines (Motors)

A 60Hz induction motor has two poles and runs at 3510rpm. What is the synchronous speed of the induction motor?

• 3200rpm

• 3600rpm

• 3800rpm

• 3400rpm

The rotor of a three phase, 60Hz, 4pole induction motor takes 120kW at 3Hz. What is the rotor speed of the induction motor?

• 1710rpm

• 1800rpm

• 1700rpm

• 1810rpm

A three phase induction motor rotates at of 3510rpm at normal voltage and frequency of 60Hz. What is the motor slip in percent?

• 3.5%

• 4%

• 2.5%

• 3%

Determine percent slip of induction motor when running at 960rpm.

• 4%

• 1.8%

• 6%

• 2%

Determine the number of poles of induction motor running at 175rpm.

• 2

• 6

• 8

• 12

A 3phase induction motor is wound for 4 poles and is supplied from a 50Hz system. What is the rotor frequency when runs at 1410rpm?

• 3Hz

• 2.9Hz

• 2.5Hz

• 3.5Hz

The rotor of a 3phase, 60Hz, 4pole induction motor takes 120kW at 3Hz. Determine the rotor copper losses.

• 16kW

• 4kW

• 6kW

• 8kW

A 15Hp, 4pole, 60Hz, wye connected, 208V induction motor draws 12kW from the line have losses as follows: Stator copper loss 900W, Rotor copper loss 300W, Iron loss 800W and Friction & Windage loss 100W. Determine the speed of the motor in rpm.

• 1710

• 1720

• 1700

• 1747

A 5Hp 4pole 60cycle 3phase induction motor takes 4500W from the supply. The rotor and stator copper per losses are 92 and 292 watts, respectively. The friction and windage losses are 72 watts and the core loss is 225 watts. What is the efficiency?

• 86.4%

• 82.4%

• 84.8%

• 88.6%

What is the ratio of maximum to full load torque in a motor having slip of 5% at full load and 25% at maximum torque?

• 15

• 3

• 2.6

• 5.2