Red Seal Industrial Mechanic (Millwright) Practice Exam

What is the purpose of overload protection in electric motors?

1. To allow motors to run at high temperatures

2. To prevent motors from overheating due to excessive load

3. To ensure motors operate at maximum efficiency

4. To increase the lifetime of the electrical supply

The correct answer is: To prevent motors from overheating due to excessive load

Overload protection in electric motors is critical for preventing overheating caused by excessive load conditions. When a motor experiences a load that exceeds its design capacity, it can draw more current than it normally would. This increased current generates additional heat, which can lead to thermal damage or failure of the motor windings if not controlled. By incorporating overload protection, such as thermal overload relays, the system can detect when the current is beyond safe operating levels and disconnect the power before permanent damage occurs. This mechanism is essential for maintaining the integrity and operational reliability of the motor, thus ensuring that it operates within safe thermal limits. The primary goal is to protect the motor from conditions that could lead to a premature failure due to overheating, thereby extending its operational life and maintaining performance efficiency. While some of the other options mention aspects related to motor operation, such as efficiency and operating temperatures, they do not accurately reflect the primary role of overload protection, which centers specifically on preventing overheating from excessive loads.