Motor Overload Protection

Many people plan their motor protection around a fuse or breaker. Fuses and breakers look at short-circuit current that happens after the motor has failed. Their job is to protect the power system from damage due to the level of short-circuit current. When they go, it's already too late for your motor. For motor protection, you should look to the overload relay in your starter.

Overload relays are defined by their protection Class. Protection is based on the amount of time it takes the overload to trip at locked rotor current. A Class 10 overload is faster that a Class 20 or Class 30 overload.