Red Seal Industrial Mechanic (Millwright) Practice Exam

Which types of motors typically require a starter?

1. High-speed motors only.

2. Induction motors and larger DC motors.

3. All electric motors.

4. Small AC motors.

The correct answer is: Induction motors and larger DC motors.

Induction motors and larger DC motors typically require a starter due to their operational characteristics. These motors, when started directly, can draw a significant amount of inrush current, which can be several times higher than their normal operating current. This inrush can lead to electrical and mechanical stress on the motor and the electrical supply system, potentially causing damage or tripping circuit breakers. A starter serves to limit this inrush current, ensuring a smoother start for the motor. Soft starters, for instance, gradually increase voltage to the motor, allowing it to accelerate gently. Similarly, in the case of larger DC motors, starters are essential for managing the initial voltage and current to protect both the motor and associated circuits. In contrast, while all electric motors have specific starting requirements, not all require a separate starter system, especially smaller AC motors, which may be designed to start without additional controls due to their lower power consumption.