3
\$\begingroup\$

I got an induction motor in a junkyard, a WEG motor made for an Electrolux washing machine.

It is a single-phase 1/2 hp 4 pole motor. It runs in 127 V and has a 40 uf capacitor feeding the auxiliary winding.

Here's a photo of an identical one I found on the internet (mine is currently disassembled):

A motor identical to  mine

Its winding can be divided into 2 sets of 4 units each: The set of inner windings (green in the picture below) and the set of outer windings (red in the picture below).

windings

After several tests I could assure it was what It looked from visual inspection, a concentric winding scheme where each unit looks like this:

concentric winding unit

Furthermore, I found out the 4 outer units are wound with two wires in parallel, having the same number of turns and inductance of the inner ones, but half the DC resistance.

In each set (inner and outer) there are 2 units wound clockwise and 2 units wound counter-clockwise, interleaved.

The stator has 32 slots, so the overall winding looks like this:

Diagram of the windings

It originally came with these connections:

A'—B ; B'—C ; C'—D ; D'—1 ; 1'—2 ; 2'—3 ; 3'—4

The capacitor was connected between A and 4', and the electrical network was connected between 1 and A or between 1 and 4' (for the two directions of rotation).

So, now that you know the motor,

My question is:

Is there a way to reconnect this to create a decent 2 pole or 8 pole motor?

Does the fact it's a concentric winding brings this any special properties?

I'm asking this because I couldn't manage to connect the units in any way that produces a viable 2 pole or 8 pole field.

The first thing I tried was undoing all the original connections, connecting only A'—C' and the electrical network to A and C. That should make an oscillating 2 pole field (not a rotating one), starting it manually should do.

But it didn't. Besides the immense current this draw (around 20 A), it would only accelerate to a rotation like 800 RPM and no further. It also sounded like it had a terribly uneven torque.

Remember those outer units were wound with two wires in parallel, so I changed that to series and tried again. Now I had less insane currents but no luck getting it to run at anything around 3600 rpm.

I tried several other configurations, also using the inner windings together to try to create a 2 pole field. I tried many possibilities but the closest I got was a very strange behavior, while using an auxiliary winding set fed with a 10 uf capacitor, where it would first accelerate to ~1800 rpm and then jump to ~3600 rpm by itself. All of that while drawing ridiculous currents, always over 15 A.

I had a different luck with 8 poles, cause it would actually run at ~ 800 rpm, but again presented ridiculous currents, didn't have a decent torque and I couldn't avoid ridiculous currents.

Anyway, I'm not understanding how it can be failing even to make a 2 pole oscillating field. It looks like it's somehow producing additional poles.

Could the radial motion of the current in the concentric winding (from the outer turns to the inner turns and vice-versa) play any role in this?

Thanks!

\$\endgroup\$
1
  • \$\begingroup\$ The limited number of rotor cores prevents 8 pole and 2 pole demands 60 V \$\endgroup\$ Aug 24 '20 at 4:21
0
\$\begingroup\$

An 8 pole cannot be made with only 8 windings in opposing pairs

This should make a two pole motor, but the design voltage will be halved.

schematic

simulate this circuit – Schematic created using CircuitLab

\$\endgroup\$
5
  • \$\begingroup\$ Just a question: When a current flows in the same direction in any two coils in this diagram you made, does this mean those coils will be producing the same pole? Just asking cause in my diagram for example, a current going from A to A' produces the opposite pole of a current going from B to B', cause I always used the prime to refer to the inner leg of each core (but they're wound in different directions). \$\endgroup\$ Aug 24 '20 at 5:12
  • \$\begingroup\$ yes that's my intention, eg left-to-right makes a north \$\endgroup\$
    – Jasen
    Aug 24 '20 at 5:19
  • \$\begingroup\$ Yes a 2 pole at 60V works if you have a VFD now if only he had two motors locked in phase on same shaft but series wound as 2 pole then he has twice the power half speed at same line voltage. Stil a waste of effort except for the learning process.. now get a new washer motor from the dump and make a VFD for a lathe using DC to sine /cos synth Constant V/f \$\endgroup\$ Aug 24 '20 at 5:25
  • \$\begingroup\$ I took a lot of time to understand this scheme, but after simulating this using transformers in the place of opposing pairs, I got to the conclusion that the cores 2 and 4 would be producing the double the field (having the double the current) of the cores A, B, C and D, right? Is that correct? \$\endgroup\$ Aug 24 '20 at 19:54
  • \$\begingroup\$ Because if that's the case I can also reconnect the cores A to D to have the double the amount of turns of cores 1 to 4 (because they're wound with two wires in parallel). In that way I could have the same current produce the double of the field in them. So I could make a similar scheme of that you made but swtiching the groups, using 1 to 4 in the place of A to D and vice-versa, plus using all cores from A to D with the double amount of turns, in some way to increase design voltage. \$\endgroup\$ Aug 24 '20 at 19:57

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.