Bipolar Parallel or Bipolar half winding?

[Oldmanandhistoy]

Hi all

It’s like this I have two choices (well 3 but looking at 2 only) Xylotex 3axis bipolar board with 8 wire steppers, bipolar parallel or bipolar half winding?
Motor specs as follows.
Amps per phase 2.1
Phase resistance 1.1
Phase inductance 1.7 mH
Volts 75 max
Power supply is 24v at 10 Amps. I’m working on higher voltage.


First of all I think I am right in thinking I need to set the vref to double the amp rating for bipolar parallel (not possible on a xylotex) but only 2.1 Amps for half winding?

My main question would I gain anything is power using parallel at 2.5 Amps rather than using 2.1 Amps with half winding?

I’m posting this thread here because although it’s a stepper question I think it is more of an electronics question.
I am building a small MDF router for a friend he supplied the stepper motors.

Thanks in advance for any input given (man I love this site).

[ger21]

It's bipolar series with 8 wire motors. Half winding is with 6 wires.

Are you sure the motor is rated bipolar series? some are rated unipolar, which is different as well. If it is rated bipolar series, then yes, the bipolar parallel ratings would be 4.2A. If you have a wiring diagram, you should be able to check the resistance and determine which way it is rated. Make sure it's wired to the Xylotex correctly, or you'll blow the Xylotex.

It's possible that you might get higher speeds wired parallel at 2.5a, but you'll also have less torque at lower speeds. A little trial and error may be in order to find what works best.

[Oldmanandhistoy]

Thanks Gerry

I have no idea how these motors are rated I have given the information on the motor plate and what I have on a sheet that came with them. I know I can wire these 8 wire steppers half winding but cannot find any info on which would be the best for the purpose they will be used.
He wants the router for cutting RC planes and pcb.

Could you or some one else tell me how I can check which rating has been used?
If they are rated unipolar would I use 2.1 Amps to set the Vref for parallel?

[ger21]

Measure the resistance of the coils for each type of wiring, and compare it to the specs.

Unipolar amps = series amps x 1.4
Unipolar amps = parallel amps x .7

Series amps = parallel amps /2
Series amps = unipolar amps x .7

Parallel amps = series amps x 2
parallel amps = unipolar amps x 1.4

[Oldmanandhistoy]

While measuring resistance I get.
Parallel 0.6
Series 2.2
Half winding is 1.1
No idea how to measure for unipolar.

So does this mean (sorry forgot to mention I am electronically challenged)?
Guessing unipolar would be 2.1 Amps
Parallel would be 2.94 Amps
Series would be 1.47 Amps
Half winding would be 2.1 Amps

If I have this all correct then for best performance with these motors for cutting wood Parallel would be the way to go? More torque at higher speeds?

John

[ger21]

I don't know what you're calling half winding? There are 3 ways to wire an 8 wire motor. Bipolar parallel, bipolar series, and unipolar. It looks like you're calling unipolar half winding. If that's correct, then you have the unipolar ratings for the motor. I'd use bipolar parallel. Set the current on the Xylotex to 2.4a, and use a fan on the heatsinks.

[Oldmanandhistoy]

My understanding of half winding is this.

If I use only 2 wires from a phase of 4 and isolate the other 2 I am only using half the winding. This would be the same as half winding with a 6 wire motor.

To get my 1.1 I measured the resistance between 2 wires only.

Did I calculate my 2.94 Amps incorrectly for parallel?

[ger21]

I think the difference between your half winding and unipolar is that unipolar uses all the coils, each wired individually. So you get the same rating per coil. 2.94a seems correct. The Xylotex only can use 2.5a, I'd set it a little low to start.

[Oldmanandhistoy]

Thank you very much Gerry much appreciated.

In my ignorance I thought I would need 4.2 Amps for parallel 2 x unipolar rating. That is why I was asking the question.

Just out of interest and if you have the time (or anyone else who would like to contribute), if I had an 8 wire motor rated say 4 Amps unipolar.
I could use the motor wired bipolar series at 2.8 (or 2.5 with a xylotex) Amps ok.
But would there be any advantage using the motor half winding at 2.5 Amps where speed torque would be concerned? Or would I be right in thinking I would lose half the torque?

I’m thinking of how you would wire a 6 wire motor series compared to half winding just for educational purposes.

Many Thanks

[H500]

If you have an 8 wire motor bipolar parallel is the ideal config if your controller could handle the current.

A 6 wire unipolar mot will have the same performance when driven unipolar or bipolar half-winding. Bipolar series will give more torque at low speeds, but will have very poor speed.

[Oldmanandhistoy]

Thanks H500

I will be running the 8 wire motors parallel at 2.4 Amps.

But these motors are a perfect example of what I am trying to understand. I can see no difference in a 6 wire motor being run half winding and an 8 wire being run half winding (as above for my understanding of half winding for an 8 wire).
Unipolar rating of 2.1 Amps so parallel rating of 2.94 Amps more than my xylotex can handle.
So half winding would be 2.1 Amps within the limit for Xylotex.

But what if these motors were rated 2.5 Amps unipolar and 3.5 Amps parallel which would be the better choice bipolar parallel at 2.5 Amps (limit of Xylotex) or half winding at 2.5 Amps? New motors or drive would be the right answer I know but what if?

The information I got for half winding with 8 wire motors came from the Xylotex forum.
Not knowing too much about internal mechanics of stepper motors is this information correct? I know it is possible to run them half winding but what would be the affect?



Thanks, John

[ger21]

Forget the half winding. I wasn't thinking clearly earlier. You can really only wire themeither bipolar series or bipolar parallel. You **could** only use 4 wires and only use half the motor, but you'd probably only have half the torque. I've never heard of anyone doing this. Wire it bipolar parallel, that should be the best way to go.