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From: email@example.com (Bill Allison)
Subject: Re: Help - Power mosfets - difficult load
Date: 25 Oct 2002 03:40:59 -0700
References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
NNTP-Posting-Date: 25 Oct 2002 10:40:59 GMT
"Phil Allison" wrote in message news:...
> "Bill Allison" wrote in message
> > For the benefit of new participants, I'm not that concerned about
> > motor or battery efficiency as the winch, currently equipped with
> > crude tension sensor driving on/off relay, has power to spare. My main
> > concern is keeping within the (expensive) fets' ratings.
> ** And you have studiously ignored advice on exactly that point.
No - questioned, debated (sure - ignorantly and unwisely or with
tongue in cheek on occasions) but absolutely *not* ignored it.
> > I'm not using a permanent magnet motor.
> ** So ???
Sorry - I should have asked the question explicitly - It's natural (to
this f**wit at least)) to wonder what difference it might make to a
pulse driven motor's behaviour to have a permanent rather than pulsed
It's prompted me to wonder, for example, whether, at the low pulse
frequency it's convenient for me to use :) differences in inductance
between armature and stator windings, might result in magnetic field
pulses in one leading or lagging the other and whether therefore I
might benefit from adjusting the timing (i.e. rotating brush pack
relative to stator) to compensate for that?
> > To all - this has generated such interest and controversy that I feel
> > obliged, once construction is complete and assuming (!!??) success, to
> > post oscillograms somewhere (somebody suggest where?) to quantify just
> > how much of a problem operating at 50Hz turned out to be. So keep an
> > eye open for this thread re-awakening in a few weeks.
> ** Keep all the blown fets and post a picture later on will you.
I refuse to be unfriendly back! I'll assume there's an invisible
smiley at the end of your sentence :)
> .. . . . . ............... Phil
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