I have a project that requires the control of a 90v 4amp DC motor. The motor currently has a speed control that sets the initial speed of the motor. What I am doing is then varying that normal speed down to another slower speed using PWM to create a sinusoidal wave. The circuit works as planned, but the problem is that I am burning up mosfets. Attached is a diagram. The parts are what I had around.
Tried changing PWM Frequency from around 32k hz to 200 hz, no change in time to overheat. I also have tried to minimize the switching time on the Mosfet, which I believe to be in microseconds.
My calcs are showing that at say 45 volts, the motor is drawing 2 amps, which equates to P = 2 ^2 * .3 ohms (mosfet resistance) = 1.2 watts running through the mosfet. This can ramp up as high as 4^2 *.3 or 4.8 watts at full power.
Should I change out the Mosfet to one that can handle the voltage and amp load but with like .07 ohm resistance? Or is my circuit in need of help? or both?
Mosfet burning up is IRF9530 P-Type
See attachment
Tried changing PWM Frequency from around 32k hz to 200 hz, no change in time to overheat. I also have tried to minimize the switching time on the Mosfet, which I believe to be in microseconds.
My calcs are showing that at say 45 volts, the motor is drawing 2 amps, which equates to P = 2 ^2 * .3 ohms (mosfet resistance) = 1.2 watts running through the mosfet. This can ramp up as high as 4^2 *.3 or 4.8 watts at full power.
Should I change out the Mosfet to one that can handle the voltage and amp load but with like .07 ohm resistance? Or is my circuit in need of help? or both?
Mosfet burning up is IRF9530 P-Type
See attachment
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