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

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
>
>
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