Mauricio,

    Check out  http://www.ep.liu.se/exjobb/isy/2002/233/exjobb.pdf

Pete

Mauricio Jancic wrote:

> Hello people,
>
>         Have the following problem:
>
>         We (me and Dennis Crawley, also a piclister) built the abob=
e
> circuit to control, using PWM, the speed of a series wound motor. I=
t
> worked fine at the factory, with no problems until we bring it to m=
y
> place, where I have no GROUND connection.
>
>         The problem it presented was that it worked fine for a few =
days,
> one day, I live my place for about an hour and a half and leave the
> board powered, but with out any input signal (no PWM). When I came =
back,
> I turn on the control board, wich only sends some PWM to the power =
board
> and then I couldn=92t stop the motor anymore, even if I disconnect =
the PWM
> source from the power board.
>
>         Okay, I changed the FET (by the way it=92s a IRF 730) and t=
hough,
> ok, perhaps it has to happened, let's see if it happens again. It w=
orked
> fine the rest of the day. When my day finished, I just unplug every=
thing
> from the mains and leave it there.
>
>         This morning when I turn on the boards, it didn't work agai=
n,
> but this time the motor doesn't receive any power at all, I know th=
at
> there is pWM, the 300V bus is powered,....
>
> Any experiences to share?
>
> Mauricio Jancic
>
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--
____________________________________________
Peter Donahue
AMTS (Code Monkey)
COM DEV International, R&D
P (519) 622-2300 x2439
F (519) 622-8706

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