What is the minimum number of overload sensing units required for a three-phase motor?

For a three-phase motor, the appropriate number of overload sensing units is three, with one designated for each phase of the motor. Each overload sensing unit is responsible for monitoring the electrical current in its respective phase to detect overload conditions that might lead to motor damage or failure.

In three-phase systems, it’s crucial to ensure balanced operation, meaning that if one phase experiences an overload due to, for example, a locked rotor or excessive load conditions, the respective overload sensing unit will trigger and disconnect the motor to prevent damage. Additionally, having one sensing unit per phase allows for more precise monitoring of the motor’s operational status, contributing to better protection and maintenance of the motor system overall.

This approach also supports effective troubleshooting and maintenance practices. When all three phases are monitored, technicians can accurately assess performance and make informed decisions if there is a malfunction within any specific phase, thereby enhancing reliability and safety.