The consequences of voltage not meeting the requirements

Changes in power supply voltage, whether too high or too low, have adverse effects on electric motors. When the voltage is too high (above 10%), the magnetic circuit of the iron core saturates (because in the design and manufacture of electric motors, the magnetic circuit at rated voltage is usually near the saturation point). Therefore, the increase of the main magnetic flux causes a sharp increase in the excitation current (several times the increase in the applied voltage), which increases the stator current and causes the motor to overheat, resulting in a temperature rise exceeding the allowable value and burning out.

When the voltage is too low (below 5%), the torque of the motor decreases in a square relationship with the voltage, which greatly reduces the starting torque and makes it difficult to start the motor (slow or even impossible to start); Secondly, for a running electric motor, if the load remains constant (during heavy load or rated load operation), the rotor must maintain the necessary electromagnetic torque to balance the resistance torque of the load. This forces the rotor current to increase, resulting in an increase in stator current, causing the motor to overheat, increase temperature rise, shorten motor life, and even burn out the motor.

There are many situations where the motor starts and runs at low voltage, and in this case, the load should be reduced or intermittent use should be avoided as much as possible. 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 operate for a long time between 418-36 volts.