The reason why the oil pump motor is missing phase_How to solve the problem of oil pump motor missing phase

How to judge whether the oil pump motor is missing phase

Observe the burnt coil of the motor. If it meets the following two characteristics, it can be determined as a phase loss burnt out.

① When the motor is connected in star connection, two-phase coils are burned out and one-phase coil is intact.

② When the motor is connected in a triangle, one-phase coil is burned out and the two-phase coils are intact.

Causes of oil pump motor phase loss

1. Power supply phase loss

Before the three-phase power supply is connected to the AC motor, the power supply has lost one or two phases (the power supply has a problem and one phase of the three-phase fuse is burned out), which can cause the oil pump motor to fail to start or start abnormally.

2. The terminal in the motor junction box is loose

One phase of the three-phase winding of the oil pump motor stator is disconnected, causing the motor to lose phase during operation.

3. The connection head is not connected or disconnected

If the connector in the power supply line is loose or disconnected due to external force, the motor may also lose a phase.

4. Phase loss caused by control circuit

The contactors and relays in the control circuit may be oxidized to a certain extent after long-term use, causing poor contact or long-term wear of the component action mechanism. These electrical components may malfunction when subjected to the impact of the motor starting current (generally 5-7 times the rated current), vibration of electromechanical equipment, or jamming and failure of the motion mechanism, resulting in stator winding phase loss.

5. Insulation aging

After the oil pump motor has been running for a long time, the insulation of the stator winding may age (the ambient temperature of the motor is too high for a long time, the power supply voltage is too high, or the load is too large), causing the motor stator winding to short-circuit between phases or turns , and one or more phases of the motor stator winding may be disconnected.

Solution to the lack of phase in the oil pump motor

1) The coils of three relays or contactors are connected to Y0 to monitor the phase voltage of the three phases. The normally open contacts of the three relays are connected in series and then connected in series to the contactor coil circuit of the motor. In this way, if the three-phase power is normal, the three relays are all energized, the three normally open contacts are all closed, and the contactor coil circuit of the motor can work normally; if the power supply is missing a phase, at least one relay must not be energized, the contactor coil circuit of the motor is disconnected, the contactor cannot be energized, or is forcibly disconnected, and the phase failure protection function is achieved.

2) There are many kinds of special phase failure protection relays in China. The principle is similar to the above. It can simplify your wiring and take up less space in the control cabinet.

3) Use an intelligent motor protector, which is small in size and multi-functional. It not only provides phase loss protection, but also quick-break protection, overcurrent protection, long start-up time protection, unbalanced current protection, etc.