Analysis and Maintenance of Three phase Asynchronous Motor with Phase Loss Operation
TIME：2024.11.04

According to the different wiring methods of electric motors, the current required for phase loss operation varies under different loads, therefore, the protection methods adopted are also different. For example, when a motor with Y-shaped wiring experiences phase loss operation, its motor phase current is equal to the line current, and its magnitude is related to the load carried by the motor. When the internal wire of a motor with delta type wiring breaks, the motor becomes a ∨ type wiring, and the phase current and line current both increase proportionally to the motor load. At rated current load, the two-phase current should increase by 1.5 times, the one phase current should increase by 1.5 times, and the other two-phase current should increase by √ 3/2 times. When the external of a motor with delta type wiring is disconnected, the two-phase windings of the motor are connected in series with the third group of windings in parallel between the two-phase voltages. The line current is equal to the sum of the current in the parallel winding path and increases proportionally to the motor load. Under rated load conditions, the line current increases by 3/2 times, while the current of the two windings connected in series remains unchanged. The current of the other phase will increase by 1/2 times. Under light load conditions, the line current increases from the light current to the rated current, and the current of the two-phase winding remains unchanged under light load. The third phase current increases by about 1.2 times. So when a motor with angular wiring runs in phase loss, its line current and phase current not only change with the location of the break, but also vary depending on the load. In summary, the reasons for motor phase loss operation are mainly due to the following reasons: 1. Poor environment or some other reasons causing one phase power supply to be disconnected. 2. Abnormal insurance circuit breaker. 3. Starting equipment, wires, contacts, burns or damage, looseness, poor contact, improper selection, etc. can cause a power outage. 4. One phase of the stator winding of the electric motor is open circuited. 5. The new motor itself is malfunctioning. 6. The startup device itself is malfunctioning.