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# Dingfeng Capacitor--Start capacitor size selection

Sep 8,2018

The starting capacitor is an AC electrolytic capacitor, a polypropylene or polyester capacitor, used to start a single-phase asynchronous motor.

The new motor has a nameplate on it, which records data such as motor power, current, and capacitance. If you encounter an old motor without a nameplate, how do you calculate the capacitance?

A single-phase motor with too small a starting capacitor can cause difficulty in starting. If the capacitor is too large, it will burn out the motor, so it is important to choose a suitable capacitor.

The formula for calculating the starting capacitor capacity is:

C=350000×I/2p×f×U×cosφ

I---current;

f---frequency;

U---voltage;

2p---the power factor big is taken as 2, and the power factor small is taken as 4;

Cosφ---power factor (0.4 ~ 0.8) is generally 0.8 for the motor.

Starting capacitor withstand voltage:Capacitance withstand voltage is greater than or equal to 1.42 × U, the pressure is small and easy to be broken down.