Electronic – Why do the mosfets keep breaking/ dont work

microcontrollermosfettransistors

or the past few weeks I've been trying to control a 48-volt DC motor with 4 12-volt batteries, an Arduino, and a mosfet. Even though the datasheet says it can run up to 60 volts and 110 amps, as soon as I hooked up my mosfet it got really hot and stopped ignoring commands from my Arduino and ran continuously.

After this I tried removing one of the batteries but after it's been hooked up to a different mosfet it works for 15 seconds or so, then the mosfet stops working. I'm just lost at this point. If anyone could help me with why the mosfets keep breaking I would greatly appreciate it.

Here is a link to the data sheet of my mosfets, IRF3205.

http://www.irf.com/product-info/datasheets/data/irf3205.pdf

This is what my setup looks like.

enter image description here

Long story short my setup makes my mosfets super hot and makes them no longer functional and i would m
like to know why.

Best Answer

There are some obvious problems with your circuit:

  1. You probably don't have enough gate drive voltage. Did you even look at the datasheet for the transistor you are using? If you had, you would have seen at what gate voltage it is intended to run at. Something rated for 60 V and 110 A almost certainly requires 12 V or so on the gate to get to the rated RDSON.

    With only partial gate drive of 3.3 or 5 V, the effective resistance of the FET is much higher. This causes it to dissipate enough power to heat up to the point of self-destruction.
  2. You don't have a flyback diode across the motor. There should be a diode in reverse across the motor. This is reverse-biased and does nothing when the motor is running normally. However, when you turn the motor off, it provides a safe path for the inductive kickback current. Without the diode when you try to switch off the motor, its inductance makes whatever voltage it takes to keep the same current running in the immediate short term. That means abusing the FET to the point where it conducts anyway, even though it is driven to off. That's bad for the FET.
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