a two phase ac motor

huangyhg

a two phase ac motor
i also posted this message in the electrical motors engineering forum but being a 400hz question and this the  aerospace forum.... who knows!!
"i have a very old design (from the 70's) and the information i have is pretty poor.
the schematics show a two phase ac motor which is supplied with a reference voltage of 26v@400hz. a second voltage, used for control, is a 400hz signal with a maximum of 13vrms.
i do not have any information about the relation of phases between the two signals and even more frustrating, in the drawings the motor seems to be based in a three phase motor having two of the windings connected in parallel. these parallelized windings are fed with the control signal (13v@400hz).
any idea/advice about the type of motor and control will be appreciated. obviously i don't have the motor in my hands, so any measurement can not be done before two/three months.
thanks in advance."
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it sounds like a servo for an autopilot system. the reference 26vac fixed phase must be excitation and the control would be directional/variable phase relationship controlled from a control amplifier.
there should also be additional components to a servo like this, such as a rate generator, follow-up mechanism, capacitor and torque limiting device.
the type i am used to seeing operate on 115vac 400hz excitation and a variable phase/voltage from the control amp. the phase and amplitude would determine the direction of turn and torque.