<P> There are three parts of protective devices: </P> <Dl> <Dd> <Ul> <Li> Instrument transformer: current or potential (CT or VT) </Li> <Li> Relay </Li> <Li> Circuit breaker </Li> </Ul> </Dd> </Dl> <Dd> <Ul> <Li> Instrument transformer: current or potential (CT or VT) </Li> <Li> Relay </Li> <Li> Circuit breaker </Li> </Ul> </Dd> <Ul> <Li> Instrument transformer: current or potential (CT or VT) </Li> <Li> Relay </Li> <Li> Circuit breaker </Li> </Ul>

Why must electric motors need overload protective device