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From: email@example.com (Eric Y. Chang)
Subject: Re: Help - Power mosfets - difficult load
Date: Wed, 23 Oct 2002 18:27:52 +0000 (UTC)
Organization: California Institute of Technology, Pasadena
References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
NNTP-Posting-Date: Wed, 23 Oct 2002 18:27:52 +0000 (UTC)
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Phil Allison (email@example.com) wrote:
: Check out ANY professional DC motor drive - they all whistle - 1
: to 5 Khz is the norm for good battery efficiency. At low speeds the benefit
: can be 10 times lower drain for same speed and torque.
Really? How about DCP or Curtis 1221?
As for good battery efficiency, the lower frequency audible rates are tough
on lead acid plates due to ripple current which cannot be filtered with a
cost effective bank of capacitors. 1-5 khz is selected for other reasons,
such as sensing requirements or the fact that recoil forced commutation of
SCR's commonly used in the lower frequency devices require this much time.
See www.evdl.org, www.crest.org for archives.
: The PWM buck regulator is the same principle, inductance in the
: DC motor will keep the current almost at a steady value if the PWM frequency
: is high enough and there is a freewheeling diode in place.
this is correct
: . . . . . . .. ................. Phil
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