The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: firstname.lastname@example.org (Bill Allison)
Subject: Re: Help - Power mosfets - difficult load
Date: 24 Oct 2002 00:37:20 -0700
References: <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: 24 Oct 2002 07:37:20 GMT
"Phil Allison" wrote in message news:...
> "Eric Y. Chang" wrote in message
> > Phil Allison (firstname.lastname@example.org) 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
> motor ??
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.
> 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 ?
I'm not using a permanent magnet motor.
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.
> . . .. . .............. Phil
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup