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

doug98105 wrote:

> Peter,
>
> I know very well why the motors burned out. We're using the machine
> to bar feed small parts. Once every year or so, we get a jam up of
> cut-off parts which stops the Z axis from moving forward. Since it
> runs unattended the servo burns up before anyone notices the jam up
> problem.
>
> Normally I assume the servo amplifier would error-out with an over
> current condition before the motor burned up except the machine
> builder chose to disable that function to get more performance out of
> the motors (dumb??).

Gasp! That may be illegal! Don't ever let OSHA catch you with a disabled
safety feature.

Do they really NEED that extra bit of performance?

> The motor builder suggested the fuse or circuit breaker solution.
> They have become very familiar with this situation. I asked if other
> users of this machine were having servo problems and had they sold
> many replacement motors? The answer was, "yes, hundreds."
>
> As I mentioned, the motor builder now offers this motor with a built-
> in 7 amp circuit breaker. Unfortunately, the circuit-breaker type
> motor won't fit my particular version of the machine because of
> interference with the circuit breaker cover and the machine
> structure.

Well, if a 7 A fuse will hold without fatigue failure or nuisance trips, then
I'd definitely put it in. I'd also keep in mind that the maker of this machine
is some sort of suicidal nut, and never buy anything from them again!

> Since the motor builder is using the 7 amp breaker I'm guessing that
> must be a reasonable value for this motor. They tell me they have
> had none of their breaker-ized motors burn up.
>
> I have since gotten the info from the motor builder regarding the
> circuit breaker they're using.

Well, there's no reason except convenience to the motor manuf. for
the breaker to be ATTACHED to the motor, so you should be able
to put it anywhere. Since this is apparently a TESTED retrofit, then
I'd go with the breaker, rather than spend the next couple months
worrying when the fuse is going to fatigue.

Jon