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. 73" de i8CVS Domenico ----- Original Message ----- From: "Greg D" <[email protected]> To: "David Palmer KB5WIA" <[email protected]> Cc: <[email protected]> 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: > > > > http://kb5wia.blogspot.com/2012/03/az-el-antenna-system-new-70cm-yagi-and.ht ml > > > > 73! > > > > Dave KB5WIA > > _______________________________________________ > > Sent via [email protected]. Opinions expressed are those of the author. > > Not an AMSAT-NA member? Join now to support the amateur satellite program! > > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > _______________________________________________ > Sent via [email protected]. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
