[amsat-bb] Re: Motor for Yaesu G5500 Azimuth Rotator?

[Joe Fitzgerald]

On 2/24/2012 8:14 PM, Phil Karn wrote:
> Fortunately, the problem of
> tracking a LEO satellite with a deadband of 5-10 degrees is a very
> non-demanding problem. That's why most hams are still doing it with
> primitive, bang-bang control.
>

I had occasion to install a Pro-sis-tel rotor for a nearby ham a while 
back.  I beleve they presently ship with DC motors, but early models had 
a little (by industrial standards) three phase motor .. I think 1/8th 
horsepower.  I did not have a chance to reverse engineer their 
controller, but it was not particularly sophisticated.  They simply 
pulsed 60Hz AC from a 24V transformer when they wanted to accelerate or 
slow down.  I am not exactly sure how they generated torque since there 
was no evidence that they did anything to shift the phase of the three 
windings.  Of course my imagination started thinking about using 
industrial variable speed drives with it.   The long cable from the 
shack to the tower is a concern ... most industrial drives specify a 
length limit to to the motor in an effort to minimize reactance.    I 
suppose you could put the power electronics at the rotor, but lightning 
concerns give me pause.

-Joe