[ausev] MOSFETs for contactors?

[Gil Dawson]

Mike--

At 10:17 A -0600 12/22/06, MLAB wrote:
>Here in my Mouser catalog is a Fairchild FQA65N06 power MOSFET in a
>TO-3P thru-hole package measuring a couple of cubic centimeters, rated
>for 60V drain-source voltage and 72A drain current.  (And I can get
>bigger ones.)

>  What am I missing?

The one thing that I think of most is the peak inverse voltage.  It 
wouldn't take much inductance in the surrounding circuitry to pop the 
substrate with a back-EMF of a thousand volts when that monster 
switches.  You might be able to fix that kind of problem, if it 
exists, with a parallel reverse-biased diode atop a Zener to shunt 
away whatever overshoots show up above the Zener voltage.

Also, pay attention to shielding -- a large delta-I over a small 
delta-t would produce a large, short magnetic pulse that will induce 
current in anything nearby that looks like a conductive loop. 
Conceivably, such a pulse could melt a small washer.  More likely, it 
could fry a delicate circuit that's too near by.

Read the application notes carefully, and ask Fairchild for some 
engineering help.  You know they would be delighted to serve the EV 
market if they can.  Wouldn't it be great to find an EV buff among 
their account reps?  Wouldn't he be glad to have ausev for an account?

You are not alone.

--Gil