A two phase AC motor 2

[zape]

I need help.

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 coils connected in parallel. These parallelized coils 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.

 

[Skogsgurra]

These motors are usually aircraft motors. The 400 Hz system is used also today. It makes everything electromagnetic smaller and lighter. Which is good when up in the air.

Visit aircraft technology sites. There should be some information available. Or join a forum for aircraft technology.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Compositepro]

It doesn't exactly match your description but it sounds like you may have a synchro motor. These are used for precise motion control where one motor will follow another's position. No electronics is needed. The stator is designed like a three phase motor and two, or more, motors are wired in parallel. These leads are traditionally labeled R1, R2, R3. The rotors are single phase and labeled S1,S2. Power is applied to the rotor winding. I have some from WWII aircraft. Fun to play with. Any motor will control the others and you can feel the torque feedback.

 

[sreid]

You have what is called a two phase AC servo motor.

http://www.electricmotors.machinedesign.com/guiEdits/Content/bdeee4a/bdeee4a_3.aspx

 

[waross]

Hi Compositepro;
What you know as a synchro motor I know as a selsyn motor. (Self Synchronous).
respectfully

 

[zape]

Thank you all for your support.

Sreid, I think you are right. The link you provided describes the use of a fixed voltage reference for a winding and a variable one for the secondary, and that's what I see in the drawings.

There is a fixed reference to the main winding, and the output of a power amplifier conected to the secondary. So I guess this amplifier is fed with an error signal and it shall modify the amplitude and phase (+90º, -90º with respect to the main voltage phase) in order to control speed and direction.

What I do not understand, mainly due to my ignorance, is the fact of being the two windings isolated.

Besides, it's not clear the motor control. For example to start the engine, do I need the two voltages? Are these motors similar to single phase motors which uses an auxiliary winding for starting? My logic says that I need the two voltages, being the variable one the one starting, acelerating and stopping the motor, but I don't understand how the motor is manufactured in order to behave like that.

I found this other link but it does not add more information than the one from sreid:

http://www.ibiblio.org/obp/electricCircuits/AC/AC_13.html#xtocid892252

 

[Skogsgurra]

The inventor of induction motors, Nicola tesla, built his motors as two-phase motors with two sine voltages, 90 degrees apart.

He got the idea when studying basic trigonometry in scool and noted that, in an orthogonal system, you plot sine(a) along one axis and cos(a) along the other, you get a circle (the well-known Lissajous figure).

To run the motor, you need the two voltages. Not only for starting. It is probably possible to start the motor with two phases and then disconnect one phase, like you do with normal single-phase motors with auxiliary starting winding. But that is not how this motor is designed to work.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...