What is the purpose of thermal relays in motor circuits?

The purpose of thermal relays in motor circuits is to protect against overload conditions. These relays are designed to detect excessive current flowing to the motor, which can occur when the motor is subjected to mechanical jams or other factors that increase its workload beyond safe operating limits. When the current exceeds a predefined threshold, the thermal relay activates, interrupting the electrical supply to the motor. This action helps prevent damage to the motor due to overheating, ensuring its safe and reliable operation.

In contrast, the other options do not accurately describe the primary function of thermal relays. While regulating voltage or controlling current flow pertains to other electrical devices, thermal relays specifically focus on overload protection to maintain the integrity of the motor circuit. Improving energy efficiency is more relevant to other technologies or devices that enhance performance without compromising safety.