When the supply voltage is rated, the influence of the power frequency reduction on the operation of the motor?
As the power frequency decreases, the synchronous speed decreases, and the speed of the asynchronous motor is reduced, which results in the decrease of the fan air volume, the difficulty of heat dissipation and the increase of the temperature rise of the motor. Thus, the decrease of frequency will increase the stator current of the motor, decrease the power factor, decrease the efficiency and increase the temperature. Therefore, when the power frequency is lower than the rated value of 0.5HZ, the motor is not allowed to be put into operation.
How much lower? The most obvious is the lower speed, the input current increases, more than the rated current continuous operation, serious overload, will soon smoke burning.
When the supply voltage is rated, the induction electromotive force formula shows that the stator electromotive force is basically the same, which inevitably results in the increase of the flux per pole of the motor, that is, the excitation current generated by the magnetic flux increases. The excitation current is a reactive current, and its increase leads to a reduction in the power factor of the motor.
