Why do inverter of a motor need capacitor? More specifically, a Tesla model 3 induction motor case. But in fact, almost all electrical vehicle's motor has film capacitor. Film capacitor is an important part at inverter, IGBT, or SiC mosfet module. But, why does a inverter of a EV motor needs capacitor?

Is it used to correct power factor? We know for sure that motor coil is inductance. It causes phase lag and power loses. Does the capacitor compensate it?

Also, I googled. Single phase induction motor has a start and a run capacitor. Tesla model 3 is with a 3 phase induction motor. Does it means that it will has 3 run and start capicitor?

Sorry I am new at electrical parts. Please correct me.

Thank you very much!


1 Answer 1


No, it has nothing to do with correcting power factor. The bus supplying the inverter is DC.

It's because there is substantial inductance and resistance between the battery and the switches that make up the 3 phase inverter, and if they were to switch without any capacitance on the local bus, there would be a substantial voltage drop and probably a lot of ringing due to the series inductance and parasitic capacitances.

This would cause EMI, issues with control of the motor, losses, extra stress on the switches, and probably other bad things I'm not thinking of off the top of my head.


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