For single-phase motors, only the size and relative stability of the supply voltage need to be considered, while for three-phase motors, the balance of the supply voltage must also be considered. The imbalance of the power supply will have different degrees of negative impact on the current, torque, speed, temperature rise, vibration and noise parameters of the motor.
<h1 class="pgc-h-arrow-right" data-track="2" > the change in current and temperature rise</h1>
When the three-phase voltage of the power supply is unbalanced, the most obvious impact is the change of current, especially when the motor is running at the rated voltage and rated speed, the unevenness of the current is very large, and the unevenness of the current is far greater than the voltage unevenness. Unbalanced voltage, will produce a magnetic field in the air gap between the motor stator and the rotor opposite the direction of the motor rotation magnetic field, thereby changing the current size in the motor stator windings, as well as the current frequency of the rotor part, especially the impact on the rotor part is larger, and the rotor loss will also increase significantly.
Due to the increase of the current and the resulting increase in loss, the heat loss of the motor directly increases, and it is intuitively manifested as an increase in the temperature of the motor, that is, the temperature rise performance of the motor becomes poor.
<h1 class="pgc-h-arrow-right" data-track="14" > the change in motor speed and torque</h1>
In order to better understand the relationship between speed and voltage, we can analyze it according to the limit state of the motor's lack of phase. When the motor is out of phase, the vibration increases, the temperature rises, the speed decreases, the current increases, and there is an abnormal sound, and there will be a lot of noise when starting and cannot be started successfully. After the motor lacks phase, the motor is weak, that is, the torque becomes smaller, and the motor stator winding will soon burn out. When the supply voltage is unbalanced, the symptoms are the same as the phase absence, but the severity is slightly milder.
<h1 class="pgc-h-arrow-right" data-track="15" > changes in motor vibration and noise</h1>
The vibration and noise of the motor can be divided into mechanical and electromagnetic, when the power supply voltage is unbalanced, the electromagnetic vibration and noise will be particularly obvious, and the vibration and noise performance of the three-phase motor when the phase is missing, that is, the limit state of voltage imbalance.
The above unofficial content is only a personal opinion.