Traditional squirrel cage of high voltage motor

The simplest estimation method is to get the calculated reactance x of the loop according to the impedance voltage of the transformer on the power supply side of the motor, and then add 6 times the capacity of the motor to be started with the transformer with load before starting the motor. That is, S, U0 is the unit value of the low-voltage side voltage of the transformer, which can be 1.

This calculation is not very accurate, but it is enough to estimate. See the following formula.

U=U0/( 1+SX)

The power of step-down starting motor mainly depends on the capacity of your power supply transformer.

When the motor power is greater than 5% and less than 25% of the transformer load, step-down starting can be adopted.

Generally speaking, the requirement of motor start-up is that the voltage drop of power grid caused by frequently started motors is not more than 10%, and that caused by infrequently started motors is not more than 15%.