Variable speed control of
a 3-phase azimuth motor

The following infomation about how to make a variable speed control of a 3-phase azimuth motor was posted in the Moon-Net reflector by Roland ON7RB. I found the subject so interesting that I decided to put it in this page.

On 2-September-1999 ON7RB wrote:
Hello OM,

Some time ago I asked on this reflector if anyone had a solution for the problem of reducing the speed of the 3-phase motor I use for azimuth rotation. The replies were either "the solution is very expensive" or "if you find it, let me know".

Well, I found a solution that is both simple and inexpensive.

In HR Jan 81, WB4EXW published an article on "Pulse-position control of the CDE Tailtwister rotor". I still use such a system on the portable eme array. It uses 2 NE-555 timers, one for pulse rate and another for pulse width. It triggers an electronic switch, a Triac 2N6071 which gives full wave ac control to the rotor motor.

For a 3-phase motor, the simple triac won't do the job. I got 10 Amps Solid State Relays at the fleamarket in Friedrichshafen and set up the system as follows :

There is no more jerking and twisting when I rotate the array now :-)))

C U on the moon and 73's de Roland ON7RB

(Note: I'm not showing any E-Mail address here in order to avoid them from being collected by SpamBots. You can possibly find the E-Mail addresses of the above OM at QRZ.COM.)

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