Nate Electrical Practice Exam

What is a primary use of the heater in a motor starter?

1. To close contactors

2. To measure amperage

3. To control the motor's temperature

4. To limit the current flow

The correct answer is: To control the motor's temperature

The primary use of the heater in a motor starter is to control the motor's temperature. In industrial and commercial applications, motors can generate considerable heat during operation, which can lead to overheating and potential damage if not managed properly. The heater, often part of a thermal overload relay, works by monitoring the current flowing through the motor. When the current exceeds a certain threshold for an extended period, indicating that the motor may be working harder than it should (which could be due to a mechanical issue or overload conditions), the heater absorbs heat and the thermal element can initiate a trip, which disconnects power to the motor. This protective measure is critical in preventing overheating, ensuring that the motor operates within safe temperature limits. This function not only extends the life of the motor by preventing thermal damage but also enhances safety by reducing the risk of fire due to overheating. Thus, the heater plays a vital role in maintaining the operational integrity and reliability of motor systems.