Re: [CAD_CAM_EDM_DRO] Re: Stepper Dissasembly

mariss92705@... wrote:

> Hi,
>
> I understand your point of view, but I have to deal with situations
> when "junk goes wrong".
>
> I had someone (no one on this group) that hooked up and destroyed 6
> drives in succession on a motor he had liberated from a dumpster. I
> had him send me the offending motor and it had a shorted turn on one
> phase. An ohmmeter wouldn't show it but an inductance bridge did.

Gee, I hope those weren't your drives! You'd think he'd notice, maybe after
blowing two drives, that there was something wrong? I can't believe anyone
would just keep throwing money at it like that.

If they WERE your drives, how come they blew up? Shouldn't the current
limiting keep it from frying? (I guess if there was NO inductance in the
winding, the current could rise to damaging levels before the limit circuit
could respond. This is a real problem with IGBTs, which have positive
thermal coefficients, but MOSFETs generally are pretty rugged in this
regard.)

Jon