Two-phase induction motor

The demonstration illustrates support material for a first year introductory Electronics module, and is prepared in the Undergraduate Hardware Electronics Laboratory of the Department of Computing and Electronic Systems at the University of Essex, Colchester UK.

It uses a set of deflection coils that would have generated the scanning raster pattern on a TV display tube. The magnetic axes of the coils are at 90 degrees to each other, and they are designed to provide a uniform magnetic field across the diameter of the tube. In a 625 line/50 field/sec TV system, they would be fed with sawtooth current waveforms at 15.625 kHz (horizontal) and 50 Hz (vertical). Here we drive both coils, via an audio power amplifier, with 50 Hz sinewaves from separate, but highly stable, oscillators that enable their relative phase to be set precisely.

When the phase difference between the 50 Hz sources is 90 degrees, a constant magnitude rotating magnetic field is generated within the coils. This can be shown with a search coil, but more convincingly by making it act as a two-phase induction motor. When the phase difference is zero or 180 degrees, the field has no rotational component and the rotor is stationary.

Category:

Science & Technology

Tags:

• electric
• induction
• motor
• two-phase
• rotating
• magnetic
• field
• University
• of
• Essex

[chiefer99]

Absolutely amazing job! Your first application was the principle a resolver operates on correct?

[james9149]

Yes; driving one of the main coils and synchronous demodulation of the 2 sense coil outputs would enable angle to be found as arctan of demod. outputs. However, easier to drive both main coils with cos() and sin() as for motor, and use 1 sense coil. Comparing phase of its output with one of the drive signals would give direct info. on angular position.

[gddeen1]

Best Ive seen so FAR!

[ntn888]

Very well presented.

[definitionofis]

By the way, that tiny current is likely from some residual magnetism in the rotor, which theoretically has zero magnetism when no current is applied to the motor.

[definitionofis]

Nobody answered. So I will take a try at it.

I think the answer is no, because the only way to induce a magnetic field into the rotor is to apply a voltage to the same stator, where you want to extract the energy.

Could it be primed, like a water pump ?

I doubt it.

Would it have to be at the same freuency as the rotation of the propeller, lagging ?

Difficult to do, at best.

I say forget it.

Good webpage here about such motors:

phys unsw edu au/hsc/hsc/electric_motors1 html

[ppsjsh]

is it possible to use a motor from sewing machine to use as wind turbine? it has no magnets, i think its induction type. it produces like .5 milliamps when i turn by hand. it runs on 120V @ 95A. think you can help. thank you

[chiefer99]

Awesome. Perfectly explained!

[urveen]

Thank you. Very informative and clear.