[amsat-bb] Re: Motor for Yaesu G5500 Azimuth Rotator?
jfitzgerald at alum.wpi.edu
Sat Feb 25 06:46:56 PST 2012
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.
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