Solution for mosfet voltage protection

[seyyah]

Help me with a practical problem.

There's a 55V/63A mosfet driving a dc motor with the parameters of Ra=1.2 ohm La=16mH. To drive the motor a 20KHz pwm is used. The supply is 30Vdc. The motor is a 24V brushed one. Anyway, sometimes the mosfet is blown out under the heavy load. I'm suspicous from the created voltage due to the switching of the inductance. So my questions are;
1- Is this mosfet's voltage rating enough?
2- What can i use to protect the mosfet? (What type of snubber and how to size it?)
3- May the reason be different from the one that i am suspicous from?

 

[Nimer]

mosfet protection circuit

hi

consider the driving circuit does it swirch the mosfet as required and does the mosfet frequency and drive circuit work well at 20khz (check the datasheets) .

on the other hand i advice you to exchange your mosfet with an IGBT since it has a better protection wise parameters .

the ratings of the chosen mosfet are good but eliminate any damage cause by high voltage spikes try raise the mosfet voltage ratings up to 100 volts at alower current since i dont think you need 63 A to drive the motor ,I suppose you are using a step down or a bridge pwm drive .

hope you fix it .

regards

 

[rohitmenon_20]

mosfet protections

Hi
I hope you have placed a freewheeling diode in parallel with the MOSFET. You may have go for snubber circuit if the problem persist.

 

[PaulHolland]

mosfet motor protection

Hi, The voltage rating of the MOSFET should be more than 3 times the normal voltage,. so 3 * 24 = 72 Volts min. best 100V. current also. do not forget a diode across the MOTOR to protect your MOSFET !!.

Paul.

 

[seyyah]

mosfet protect

Replacing the mosfet with a 100V one seems solved the problem so far.

 

[Mr.Cool]

protection mosfet transistor snubber circuits

i like the idea of going to 100V. your motor's winding inductance is large, so there is probably some killer voltage spikes that need to be properly addressed. mosfets come with their own body diode (well, 99% of them do) and so you should not need to put external another diode!

check the datasheet for the diode conduction ratings, you want it to be fast and can carry the current.

Mr.Cool

 

[harimelath]

best mosfet protection

Hi
I hope the MOSFET Vds is not sufficient for the application, It should be at least 100volts, try IRF3710, This is rated at 100V with a very good Rds. may also try to put a ultra fast diode across the MOSFET for snubbing,. Try MUR8100 or BYM36E.
Thanks
Hari