On 3/4/23 13:53, Leonardo Marsaglia wrote:
Hi guys.
Sorry for the OT but I'm having a strange behavior with my spindle and I'm
a little worried.
The problem I had today for the first time is the spindle was getting
really hot and started to slip (you could hear the frequency from the
inverter was on spot but the rotor sometimes wasn't even turning).After a
few seconds of slipping the VFD triggered the over current alarm and the
spindle was stopped. Once the the spindle cooled down it worked perfectly.
This never happened before but also I must clarify that today the ambient
temperature reached 40⁰C and I'm sure that under that roof where the router
is placed there were 45⁰C so I suspect this has something to do with the
problem.
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.
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.
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?
The spindle is rated 11kw of max power output and is air cooled. It has a
built in fan motor so it doesn't rely on spindle speed for cooling. It
always gets warm (there are several labels on the spindle’s body for
caution because of the heat) but nothing like today.
Could this be normal because of the extremely hot days I'm having here?
Should I think about changing bearings or even rewind the motor? I've only
had the over current alarms when the spindle was too hot.
I will be really thankful if you can share your thoughts about this.
Thanks for your help as always!
Leonardo.
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
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/>
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
