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...
73!
Dave KB5WIA
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...
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
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
Hi Greg,
Hey, thanks!
Good question about how long it takes the windings to degrade. Haven't tested this myself, but I'd seen a post a while back where someone measured current draw on the motor, and found that it's actually almost the same between normal operation and a full stall. That also could be the reason why the 1-Amp fuse I installed in the controller (which was barely enough to run the motors without blowing - a 0.75-Amp fuse I tried blew) never blew throughout my motor stall. So .... with similar current and voltage in a stall as compared to normal use, that should mean the power consumed (and heat generated) would be similar whether the motor is running or stalled.
When I was bench testing the rotator, after maybe 5 full trips to 450 degrees and back (perhaps 10-15 minutes of continuous motor operation) the thermal switch rated at 75C tripped open. So that means the switch is sensing the motor heat, and that it seems in normal operation the motor can go from ambient to 75C (or more) in 10+ minutes. Hard to tell what the failure temp of the enamel wire in that motor is, but let's guess 120 degrees to be conservative. That would give a very rough ballpark of 20 mins stall (or 20mins continuous back-and-forth with no stops) to raise the temp by 100C to cook the motor.
You're right about thermal mass and winding temps -- certainly the windings will be hotter than the motor chassis. Will cutting power to the motor when the chassis gets to 75C protect it? Don't know for certain, but after my last experience, I'm adding this insurance, since it's better than no protection! :-)
(doesn't beat common sense tho -- if I had more of that, I would have checked antenna clearance before letting the computer run the sat array automatically!)
73 de Dave KB5WIA!
On Wed, Mar 14, 2012 at 2:41 AM, Greg D [email protected] wrote:
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
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i8cvs