Re: [CAD_CAM_EDM_DRO] RE: Re: RE: Re: Mavilor Servos, how to test + Identify

Hi, i worked with printed circuit motors(pcboard armature) or low
inertia/mass rotor. they will overheat real easy if you overload them. the
circuit board armature usually warps and grounds out on the magnet
assemblies rendering them useless. If you open one up the magnets will loose
considerable magnetizm if the maximum gap for the magnet assy is exceeded. I
have a bunch of those magnets which i put on 2 plates of steel and hit it
with a magnacharger. big tuff magnet but pull one plate loose and they all
loose a lot of magnetism. cul brian f.

----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, November 22, 2001 4:33 PM
Subject: Re: [CAD_CAM_EDM_DRO] RE: Re: RE: Re: Mavilor Servos, how to test +
Identify


> John Harnedy wrote:
>
> > > Thanks Jon for the quick reply.
> > > Did some further examination
> > > Nameplate says DC servo motor, amazing what one can find out when i
open my eyes!!!
> >
> > Ahh, that helps.
> >
> > JH Took off the nameplate and here are the best guesses that we could
make ( got the better half to assist as my eyes are suffering from 2 decades
of long days and nights on CAD)
> > Ncm = 22? or 27?
> > V 7? could be a 0, 5 6, or 8
> > RPM 3000
> > KW 0.2 or 0.7
> > Amps unable to read anything
>
> Ugh. A nameplate that can't be read isn't much good!
>
> >
> > Unfortunately, there are lots of variations. Are the brushes all the
same, and in
> > the same plane?
> > JH Just 4 at one end on same plane, with opposite ones connected
together
>
> OK, a 4-pole DC motor, standard connections.
>
> > Many servo motors have temperature sensing devices (thermocouples,
thermistors
> > even thermostats) inside to warn the machine control of overheating.
Some really
> > oddball servos have windings that either boost or buck the permanent
magnet
> > field.
> > JH Unable to find any thermal protection device
> >
> > Check the Green/Yellow wire to see if it is a case ground.
> > JH yes it is
>
> Good, now we have 3 wires pretty well identified.
>
> > Check the resistance on the brown and blue wires, maybe that will
indicate
> > something. Inspect the interior of the motor with a flashlight and see
if there is
> > a cooling fan.
> > JH no specific cooling fan, but the motor construction is " disc
armature"printed" motor" with 8 poles.
> >
> > Put a voltmeter on the brown and blue wires and turn the motor.
> > If you get a voltage, it may be a tach winding.
> > JH yes got up to 8VDC peak on fastest hand turn i could achieve
>
> Well, it seems brown and blue must be motor power, as they are heavier on
the
> larger motors. Could be about 15 V/1000 RPM, so a 45 V motor, give or
take
> about 50%. Hmmm, a disc armature motor. These aren't real powerful, and
> need a lot of amps, normally, as they have VERY few turns of 'wire' on a
> PC board.
>
> It would be real useful to figure out the peak current rating, as if you
exceed
> that you will demagnetize the magnets, and the motor will be junk.
>
> Jon
>
>
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