"RedRoby" wrote in message
...
Hi to all!
I need iof your help.
I have a lot of 400Hz Muirhead Servomotor-Tachometer generator mod.
15M81A,fom Mil surplus.
For 400Hz supply isn't a problem but I Don't have idea how to apply or
drive
this servomotors.
This motor is supplied with a 115Vac primary plus two 13Vac control
windings, one tachometer 115 Vac primary with a secondary output.
Do you have some suggestion, scheme, application notes for use this motors
in a light CNC project?
Will be welcome application notes, schematic, literatures or URL's for
this devices..

I wonder if you can use them as motors in a CNC project. Their original use
is to convey an angular position over wires. In such a setup, two of these
motors or Selsyns as they are also called, are connected with the rotors and
stator windings in parallel. 115V 400Hz is applied to both rotor windings.
If you now turn one by hand, the other follows. Such a system is used to
convey the position of a gyro compass to an instrument with a dial.

If you want to use such a selsyn as a servo, you must apply a fixed 115V to
the rotor, and a lower voltage with the appropriate amplitude to the stator
windings. These voltages must be in phase with the 115V. If you vary both
voltages, one with a sine envelope, the other with a cosine envelope, the
motor will turn.

Meindert