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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: Help - Power mosfets - difficult load
References: <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <3DB81206.E28CA99F@rica.net> <email@example.com> <3DB963BE.939694C2@rica.net> <firstname.lastname@example.org> <3DBC2B63.146AA440@rica.net> <email@example.com>
Date: Mon, 28 Oct 2002 14:01:50 GMT
NNTP-Posting-Date: Mon, 28 Oct 2002 09:01:50 EST
Bill Allison wrote:
> Thanks John
> Useful as always. Comments below. Also, I've come across a post on
> another forum which states that my particular starter motor's static
> inductance is 70uH. Unable to verify accuracy of that, and the same
> poster also stated that resistance is 40mOhm, which conflicts with the
> 32mOhm I have from two other sources. And don't know how useful to
> know given the complex scenario of stator and multiple, commutator
> switched, inductances...
I would call 40 mohm a confirmation of your previous 32 mohm value.
This pair also gives me some idea of the minimum frequency this motor
will run well on. I would estimate that the L/R time constant is a
good maximum pulse repetition period for your PWM circuit. That comes
out to just over 500 hz. Much slower than that will cause the current
to occur in big blasts with zero current between them.
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