Is it true that motors with built-in thermal protection must also have external overload devices?

Motors with built-in thermal protection are designed to prevent overheating and potential damage due to excessive current flow. The purpose of thermal protection is to automatically disconnect the motor when it reaches a predetermined temperature, thus reducing the risk of failure.

However, external overload devices provide an additional layer of protection, particularly in situations where the built-in thermal sensors may not respond in a timely manner or may not cover all aspects of motor or circuit loads. These external devices can be tuned to specific overload conditions, ensuring that the motor is adequately protected in varying operational environments.

In specific applications, such as industrial or high-demand settings, relying solely on internal thermal protection may not be sufficient due to the potential for overload conditions that could exceed the thermal limits. Therefore, having external overload devices enhances the overall protection mechanism of the motor, ensuring greater reliability and safety.

This leads to the conclusion that the statement regarding the necessity of external overload devices, even when a motor has thermal protection, is true. The combination of both types of protection contributes to a more robust safeguarding of the motor and its operation.