Re: [CAD_CAM_EDM_DRO] Need a circuit breaker.......

The question I have is: Why are these motors "burning out"? Are they not
properly sized for the job? Unless they are seeing fault conditions
(hitting stops, brakes on etc) they shouldn't normally be overloaded to the
point of destruction.

Thermal overloads, circuit breakers etc. cures the symptom, not the problem.

>From: "Peter Seddon" <peter@...>
>Reply-To: CAD_CAM_EDM_DRO@yahoogroups.com
>To: <CAD_CAM_EDM_DRO@yahoogroups.com>
>Subject: Re: [CAD_CAM_EDM_DRO] Need a circuit breaker.......
>Date: Tue, 26 Mar 2002 09:07:49 -0000
>
>Is that the best way to protect motors from burning out? A 7Amp slow blow
>fuse will carry 7Amps minimum for ever which is above your motor rating.
>Fuses and circuit breakers are really designed for short circuit protection
>and not thermal protection.
>
>The best way to protect a motor is by embedded thermal detectors which
>detect the actual motor winding temperature but are installed when the
>motor
>is built and best suit ac motors which have stationary windings. The
>alternative is a thermal overload relay in series with the motor but this
>often trips too early as it does not have the thermal inertia of the motor.
>
>I would try a thermal overload relay and leave fuses and circuit breakers
>for short circuit protection.
>
>Regards Peter
>
>
>----- Original Message -----
>From: "doug98105" <dougrasmussen@...>
>To: <CAD_CAM_EDM_DRO@yahoogroups.com>
>Sent: Monday, March 25, 2002 11:16 PM
>Subject: [CAD_CAM_EDM_DRO] Need a circuit breaker.......
>
>
> > Group,
> >
> > It's recommended by the maker of the DC servos on my lathe that I
> > install a 7 amp slow blow fuse or circuit breaker to protect the
> > motors (2 motors burned up in last 4 years, $820/each).
> >
> > Motors are rated 4.6 amp continuous, 18.4 peak. Max volts 100.
> >
> > The motor manufacturer offers a breaker protected motor, but it won't
> > fit in my space with the breaker protruding from the side. Their
> > circuit breaker reset is sided mounted with protective cover, .63"
> > square by .813" tall (fairly small considering that includes the
> > cover). They buy the breaker from Newark, no part number is
> > available to me, though.
> >
> > Anyone have suggestions, brands, etc. I can't seem to come up with
> > much locally. What I find here are rated 32VDC, would that be okay?
> >
> > thanks,
> >
> > Doug
> >
> >
> > Addresses:
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> >
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>Addresses:
>FAQ: http://www.ktmarketing.com/faq.html
>FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>
>OFF Topic POSTS: General Machining
>If you wish to post on unlimited OT subjects goto:
>aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
>you have trouble.
>http://www.metalworking.com/news_servers.html
>
>http://groups.yahoo.com/group/jobshophomeshop I consider this as a sister
>site to the CCED group, as many of the same memembers are there, for OT
>subjects, that are not allowed on the CCED list.
>
>
>
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>bill,
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>List Owner
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