Hits:Updated:2020-04-14 09:04:34【Print】
Observe the coil burned out by the motor, if it meets the following two characteristics, it can be judged that the phase is burnt out.
① When the motor is star-connected, the two-phase coil is burned, and the one-phase coil is intact.
② When the motor is connected in a delta mode, the one-phase coil is burned out, and the two-phase coil is intact.
Reasons for lack of phase of oil pump motor
1.Power phase loss
Before three-phase power is connected to the AC motor. This power supply has one or two phases missing (the power supply has a problem, and one phase of the three-phase fuse has been burned out), which can cause the oil pump motor to fail to start or run abnormally.
2. The terminal in the motor terminal box is loose.
One of the three-phase windings of the stator of the oil pump motor is disconnected. As a result, the motor runs out of phase.
3. The connection head is connected or disconnected.
A virtual connection in the power supply line or it may be disconnected by external force may also cause the motor to lose phase.
4.Control circuit causes phase loss
The contactors and relays in the control circuit are used for a long time, and the contacts may be oxidized to a certain extent. Causes poor contact, or long-term wear of the component movement mechanism. When these electrical components are impacted by the starting current of the motor (usually 5-7 times the rated current), or are subject to vibration due to the vibration of the electromechanical equipment or the movement mechanism is stuck and malfunction, the stator winding is missing.
5.Insulation aging
After the oil pump motor has been running for a considerable period of time, the insulation of the stator windings may deteriorate (the ambient temperature during which the motor is running is too high for a long time. When the power supply voltage is too high or the load is too large), it causes a short-circuit between the phases of the stator windings of the motor and the stator of the motor One or more phases of the winding will also open.
Solution for lack of phase of oil pump motor
1) The coils Y0 of 3 relays or contactors are connected, and the phase voltage of 3 phases is monitored. The normally open contacts of the three relays are connected in series and then connected into the contactor coil circuit of the motor. In this case, if the three-phase power is normal, the three relays are all closed, and the three normally open contacts are closed, and the contactor coil circuit of the motor can work normally; if the power supply is out of phase, at least one relay must not be attracted. Close, the contactor coil circuit of the motor is disconnected, the contactor cannot be pulled in, or it is forcibly disconnected, which has the function of phase failure protection.
2) At present, there are many kinds of special phase-open protection relays in China. The principle is similar to the above, which can simplify your wiring and take up less space in the control cabinet.
3) The use of intelligent motor protectors, small size and multiple functions, not only phase-break protection, but also quick-break protection, over-current protection, long start-up protection, unbalanced current protection, etc.
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