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From: "Phil Allison"
References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
Subject: Re: Help - Power mosfets - difficult load
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Thu, 24 Oct 2002 09:36:33 +1000
NNTP-Posting-Date: Thu, 24 Oct 2002 09:27:51 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"Eric Y. Chang" wrote in message
> 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
> : 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
> 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,
** Does it not smooth the current? Then the rms value is made the same
as the average?
Does this not ( dramatically) reduce I squared R losses in the
With a permanent magnet motor and runing at lowish speed the
efficency boost is a factor of ten or more - that is pretty useful when
operating from a battery - no ?
. . .. . .............. Phil
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