On 3/4/23 18:19, Leonardo Marsaglia wrote:
Hi Gene, hope your doing well!
As well as can be expected for an 88 yo diabetic with a chest full of
parts. I bought a couple t-shirts last fall that lie a lot, says "born
in the thirties, original and unrestored, some parts still working"
IMO and unless the armature of that motor is some sort of a ferrite
compound, that temp s/n should not be a problem. Most motors can handle
temps too hot to lay your hand on them unless they are on their way out
in some sort of shorted windings failure mode. Most motor iron is grain
oriented silicon steel since about the end of WW-II, and that is not one
on its failure modes.
Indeed, from my experience with normal induction motors the temperature
this spindle reached shouldn't be a problem. I didn't measure it with a
thermometer but I felt it was somewhere in the 65ºC range. But since this
is a high frequency spindle motor and materials are a little different I'm
a little bit lost here.
The reason I mention ferrites is because there are ferrites that have a
"curie point" temp below 100C. But I've never heard of the ferrites
being used in motor armatures, just high performance transformer cores.
But that does bring up the possibility that the problem is actually the
vfd since its switching transformer is a prime candidate to use such a
ferrite compound. But that failure is in my experience, permanent
because if it passes the curie temp while energized, there is no
recovery short of returning the core to Arnold to run it thru their heat
treatment again to re-establish its magnetic properties.
Interesting, I didn't know they used materials with such a low curie point.
Well, HP did, and it hurt them bad, I guess their engineers didn't get
all the memo's. ;o)>
In both of those failures, encountered in H.P. brand power supplies at
the tv station, it was as if the core was replaced by air, and it
happened at such a low temp that the green paint on the core was not
discolored.
I'm just guessing about your setup, my only high rpm spindle is the 24k
rev water cooled one I replaced with a better one on my 6040 mill, where
the water tank is about 4 gallons and a 3 day job making a hard maple
screw only gets the tank up to 36C in my air conditioned
garage/workshop. Its insulated, 6" walls full of cocoon, and a foot of
it on the ceiling, with a measly 5k btu window AC to cool the place.
It sounds as if the motor is on its way out, but I'd not be totally
surprised to find the vfd was somehow being a problem. Measuring the
motor inductance, looking for not more than a 5% difference between the
three coils would be my first step. Next would be suitable light bulbs
on the vfd. I'd say look at its output with a scope, but that voltage
will probably destroy the scopes usual 10x probes, and high voltage 100x
probes are mail order far away.
Whats your normal wall voltage?
I have 380 volts but I didn't had the chance to measure it today. I'll do
it tomorrow. I wasn't worried about that because I assume the VFD would
trigger an alarm in case of a voltage drop or missing phase. In fact all
the servo motors are working ok. I just really hope this is a bearing
problem, although I will have to import them anyway.
To where these days?
Take care and stay well yourself.
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>
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