back emf suppression of ac motor

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moez

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Hi,

I made an invertor using PWM and H-bridge configuration. But when I attached it with heavy ac motor it destroy my circuit..
Can anyone guide me to how i can suppress the back emf of ac motor??
In dc motor, diode is attached in parallel with motor with its reverse polarity but what should I do in case of ac motor??

Thanks
 

Better to put diodes in parallel to switches. If you don't want to put the diode then you need to generate swithing sequence so that motor should never be opened in circuit.

Umesh
 

I used NMOS( IRFP450) for switching and connected diode in series after each NMOS so that no back emf will pass through the NMOS, is that the right way?
I also read somewhere that to put two 0.1uF ceramic capacitors from each terminal of the motor to its grounded case, it is better option or not?
 

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