| Abstrakt: |
The article discusses how to protect alternating current motors. Techniques for protecting are well-developed, but which to apply and how to set protection limits may differ in response to the failure cause, motor importance or system design philosophy. In the case of impending motor failure, certain signs may be detected. One such sign is that the motor fails to start when commanded, or the motor trips off the line because of excessive motor current. Other signs include a high motor temperature during normal performance. A fault on a motor circuit will draw fault current from the source as well as from other motors connected to the system. If the fault is on the circuit between the motor and the controller, the motor will also feed into the fault. |
