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The influence of the voltage is too high or too low on the motor

Date:2023-07-31   Author:XINDA MOTOR

Changes in power supply voltage that are too high or too low have adverse effects on the motor. When the voltage is too high (higher than 10%), the iron core magnetic circuit is saturated (because when designing and manufacturing the motor, the magnetic circuit under the rated voltage is generally near the saturation point).

Therefore, the increase of the main magnetic flux makes the excitation current increase sharply (several times the value of the applied voltage increase), so that the stator current increases, and the motor overheats, so that the temperature rise exceeds the allowable value and burns out. When the voltage is too low (below 5%), the motor turns short and the voltage square relationship decreases.

— Then the starting torque will drop a lot, and the motor will be difficult to start (slow to start or even unable to start);

Second, if the load of the running motor is constant (heavy load or rated load operation), the rotor will keep the necessary electromagnetic rotation short to balance the resistance torque of the load.

This forces the rotor current to increase, which leads to an increase in the stator current, causing the motor to overheat, increase the temperature rise, shorten the life of the motor, and even burn the motor.

There are many cases where the motor starts and runs at low voltage. At this time, the load should be reduced as much as possible or intermittent use. Generally, the voltage of the motor is allowed to fluctuate within the range of +10% to -5%.

If the power supply voltage is 380 volts, the motor is allowed to run for a long time between 418-361 volts.

Because the torque of the motor is proportional to the square of its voltage. When the system voltage decreases, the rotational torque of the motor will decrease a lot. If the load remains unchanged, the motor current must increase a lot to produce the required torque. If the required torque exceeds the limit of the motor, It may cause the motor to be overloaded and damaged. If the voltage is too low for a long time, the motor will heat up and burn out.

When the power supply voltage is lower than the rated voltage of the motor, the rotating magnetic field of the stator core will be weakened, and the weakening of the rotating magnetic field will reduce the induced current of the rotor winding. produced by the effect. Therefore, the reduction in these two aspects will greatly reduce the torque, and in severe cases, the motor may be difficult to start or cannot be started.

In normal operation, after the voltage drops, the motor will slow down due to the torque reduction due to the constant load, which will increase the speed of the rotor winding cutting the magnetic force lines and increase the induced current and stator current, sometimes causing overcurrent After running for a long time, the motor will overheat or even burn out. What should I do if the motor and water pump burn out? The best solution is to add a voltage regulator or booster up front.