[amsat-bb] Re: G5500 Azimuth Rotator Update
domenico.i8cvs at tin.it
Tue Mar 13 20:33:16 PDT 2012
Hi Greg KO6TH and Dave KB5WIA
I have always seen the thermal switches buried into the windings
themselves both for transformers and motors.
To prevent short circuits between turns of the windwing is better to
use # 24 fiber glass copper insulated wire for class H insulation of
motors or transformers wich windstand constantly very high temperature
around 180° C, Celsius i.e. 356 ° Fahrenheit.
I have used the above wire with success in critical thermal applications
to industrially rewind DC and AC motors working close to lead melting
fornaces in a steel plant in Italy.
----- Original Message -----
From: "Greg D" <ko6th.greg at gmail.com>
To: "David Palmer KB5WIA" <kb5wia at amsat.org>
Cc: <amsat-bb at amsat.org>
Sent: Wednesday, March 14, 2012 3:41 AM
Subject: [amsat-bb] Re: G5500 Azimuth Rotator Update
> Hi Dave,
> How long does one have to stall the motor before the windings'
> insulation starts to degrade? I seem to recall it's not very long (less
> than minutes).
> With all that thermal mass, and the insulation from the heat shrink
> tubing, is the thermal switch really going to be effective mounted that
> way? I would have thought it needed to be buried in the windings
> themselves somehow (though I can't imagine getting good thermal contact
> there either).
> Great pictures, by the way.
> Greg KO6TH
> David Palmer KB5WIA wrote:
> > Hi Everyone,
> > Here's a quick update on my G5500 Azimuth rotator story. (Recall that
> > three weeks ago I stalled the rotator after switching antennas.)
> > Yaesu Parts USA is still backordered on the replacement motors,
> > possibly some will arrive from Japan in a few more weeks (or possibly
> > not). The company that I sent the motor to in LA (Eurton Electric)
> > just gave me a quote today for the rewinding cost: $365. That's
> > close to $3X what the motors go for new (if you can find one!), so at
> > least with them it's not cost-effective to repair the motor. I'm
> > having the motor shipped back, and I'll either try to rewind it
> > myself, maybe someone else who can rewind it, or buy a replacement
> > sometime in the future.
> > To get the antennas back on the air, I decided last week that it would
> > be good to have a spare -- so I ended up purchasing a replacement
> > G5500 system and installing the azimuth rotator this last weekend.
> > Everything's working great so far! I also added a thermal cut-out
> > switch to the motor to prevent a similar stall-induced-motor-burnout
> > in the future. If anyone is interested in how I installed the switch
> > (or what a G5500 azimuth rotator looks like inside), I've added
> > pictures to my blog at:
> > 73!
> > Dave KB5WIA
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