three phase ac drives using pic microcontroller

[piyush_embedded]

hello friends,,

i am working on 3Φ ac drives and i have generated pwm waveform by pic(18f2331) controller.i have build the ckt as follows

pic18f2331 -> optocoupler -> ir2110 -> h-bridge.... first i want to simulate single phase ac drives so i have attached below ckt diagram.
but my problem is that one half bridge gets warm then other. so what is the possible solution.

thanks in advance

 

[goldsmith]

Dear piyush
Hi
Did you created enough dead time in your SPWM signals ?
Best Wishes
Goldsmith

 

[piyush_embedded]

first of all thanks for giving me reply..

yes i have maintained 2us constat dead time by micrcintroller.
but my problem is that 1 out of three half bridge is get warm then other two. i dont have connected any load across inverter yet.
have u any idea about that. its urgent please...

 

[goldsmith]

If all of the stages are the same , and just one of them is going to be warm , it can be because of dead time , too !!!!!! don't forget that we don't have any things that are really similar together . so i think the internal capacitor of your switches are different .
Try to increase dead time of that section that is dissipative . it would be cold !

 

[piyush_embedded]

yes, you are right, now i have incresed the dead time from 2us to 10us and its working!, thanks for your help.
now the problem is when i try to run 3-phase motor it can't run smoothly. and speed is also low however i give 200v dc supply.

what is possible cause for that do you know?
i follow AN900 application note from micrchip.

 

[goldsmith]

Hi again
200v dc supply. ???!!! how much is the work volt of your motor ? is that 380 volts ? if yes , why you gave it 200 volts ??!!
Best Wishes
Goldsmith