△Connection method Voltage relay protection circuit for motor phase failure

For motors with △ connection, an artificial neutral point must be made, that is, three capacitors (impedance components) of equal value are connected in a Y shape and connected in parallel with the motor. At the midpoint of this Y shape, a relay or other protective components are connected. as the picture shows. When the motor's three-phase power supply is operating normally, the neutral point voltage U00 is generally less than 10V. When the motor load is running and the phase is interrupted, the size of the neutral point voltage U00 is related to the load, and its variation range is 10 to 50V. The heavier the load, the higher the voltage, but it has little to do with the capacity of the motor. If DJ131/60CN type voltage relay is selected (the operating voltage range is 15~60V, the coils are connected in series, the long-term allowable voltage is 220V), the operating voltage can be adjusted to 20~25V; if the motor load is lower than 50%~60%, the setting The voltage is 15~20V. If the motor is connected in △, its Y-shaped impedance component can be a 0.1~0.47μF, 400V capacitor. This circuit is suitable for 0.6~55kW motors.