Why Three-Phase Diesel Generator Loses Phase?

Three-phase diesel generator is a new type of power generation equipment, with a lightweight design, reliable quality and wide range of applications. Many customers feedback that the three-phase diesel generator sometimes has a lack of motor phase during the use of it. What is the reason for the phenomenon?

The reason for the phase loss of the three-phase diesel generator motor is that the power supply line (usually a contactor or a circuit breaker) does not supply the three-phase voltage to the motor at the same time, or the line is disconnected. The phenomenon is that if the motor can rotate at no-load, it will instantly heat up and hum, and the rotation will be weak; when it is overloaded, it will just hum and instantly heat up. If the power is not turned off in time, the motor will be burned.

For three-phase induction motor, the normal operation should be three proportional AC current flow into the three proportional stator windings to produce a circular rotating magnetic field. When the three-phase current is missing one phase, the motor will appear abnormal operation phenomenon. The main reasons for the motor to cause a phase failure are the following situations.

1. Motor phase loss

Three-phase diesel generator motor phase loss is due to motor overheating. Bearing damage, loose joints, mechanical trauma, broken terminals and other reasons can also cause phase loss of the motor.
The judgment of this kind of fault can be measured by the electric block of the multimeter to measure. If the three phases are balanced, that is, the three-phase diesel generator motor has no phase loss. If there is a phase or two-phase disconnection, you can determine that the motor is out of phase.

2. Power phase loss

Power phase loss means that the power supply phase of the input motor is missing. The reasons for such failures are generally fuse or automatic circuit breaker phase loss. The lack of phase of the AC contactor, the lack of phase of the thermal relay, the lack of phase of the terminal, or a line break will also cause the lack of phase of the power supply. Diagnosing such failures is simple. Just use the voltage range to measure at the input of the motor when the circuit is on. If any one of the diesel generator's three phases shows a serious voltage deficiency, it can be determined that the power supply is out of phase.

3. Phase loss caused by control loop

The contactors and relays in the control circuit are used for a long time, and the contacts may be oxidized to a certain extent. This can cause poor contact, or long-term wear of the element action mechanism. When these electrical components are impacted by the starting current of the motor (usually 5-7 times the rated current), or by the vibration of the diesel generator or the movement mechanism is stuck and malfunctioning, the stator winding will lose phase due to this.

4. False connection or breakage of connector

If the connector in the power supply line has a false connection or may be broken by external force, it will also make the motor out of phase.

5. Insulation aging

After the three-phase diesel generator has been running for a considerable period of time, the insulation of the stator winding may be aging. The aging of the insulation of the stator winding is because the ambient temperature of the motor is too high for a long time or the power supply voltage is too high or the load is too large. The reasons for the aging is that the ambient temperature of the motor is too high for a long time or the power supply voltage is too high or the load is too large. This will cause a short circuit between phases or turns of the motor stator winding, and the motor stator winding can also be disconnected in one or more phases.