Licensed Electrical Contractor Licensed Electrical Contractor Motors and Motor Controls Questions and Answers 2

Question 1

What is the primary purpose of a reduced-voltage starter for an AC induction motor?

Accepted Answer

To limit inrush current during startup

Answer

To increase the motor's full-load speed

Answer

To reverse the direction of rotation

Answer

To provide regenerative braking

Question 2

Per the NEC, what is the maximum allowable setting for a motor branch-circuit short-circuit and ground-fault protective device using an inverse-time circuit breaker for a standard AC motor?

Accepted Answer

250% of the motor full-load current

Answer

150% of the motor full-load current

Answer

125% of the motor full-load current

Answer

175% of the motor full-load current

Question 3

Which type of motor control method uses a Variable Frequency Drive (VFD) to adjust motor speed?

Accepted Answer

Frequency control

Answer

Voltage control

Answer

Pole switching

Answer

Wound rotor resistance

Question 4

What is the function of an overload relay in a motor control circuit?

Accepted Answer

To protect the motor from sustained overcurrent conditions

Answer

To protect against short circuits in the feeder

Answer

To regulate motor speed under varying loads

Answer

To provide instantaneous trip on ground faults

Question 5

When installing a motor disconnecting means, the NEC requires it to be located where?

Accepted Answer

Within sight of the motor and its controller

Answer

At the main service panel only

Answer

In an adjacent room with clear labeling

Answer

At least 50 feet from the motor

Question 6

A three-phase motor has a nameplate FLA of 40 amps. What is the minimum ampacity required for the branch-circuit conductors per NEC 430.22?

Accepted Answer

50 amps

Answer

40 amps

Answer

45 amps

Answer

60 amps