How to tell how many poles a motor has. 4

[Evilsanta]

Hi just wanting to find information on electric motors and how to tell how many poles a motor has. Im being trained on winding motors but at present cant get my head around how to tell how many poles inside a motor. Anyone any interactive showings of how to tell? I know its each change in the windings results in a pole, ie each up and down, but I just dont get how to see it inside the motor before stripping it, any tips are greatly appreciated or if theres any books or photos of the inside of motors to show different poles and windings that would be great as well.


Thanks Alan

 

[electricpete]

Forgive me mentioning, the straightforward way to tell is to look at nameplate speed and figure it form there. 60hz motor at just below 3600rpm is 2-pole, at jut below 1800rpm 4 pole, just below 1200rpm6 pole.

I'm guessing you already knew that. By looking at the connection end, you can figure out how many parallels (start at a phase lead and see how many different coils connect directly to it. I guess there's a lot more an experienced winder can tell looking at the endwindings. For me I usually end up confusing myself.

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(2B)+(2B)' ?

 

[cranky108]

I would question if you really want to know how many poles or how many windings? Motors may be very complex, and the question maybe how complex are you needing to get.

A two pole single phase induction motor has 4 windings, and a two pole three phase motor has 6 windings.

But if you are looking at DC motors that may be totally different.

 

[electricpete]

a two pole three phase motor has 6 windings.

Just a minor note on terminology – I’d use “group” instead of “winding” there.

i.e. a 2-pole 3-phase motor has 6 “pole-phase groups” or simply six “groups”. Coils within a single group are both physically and electrically adjacent.

For 3-phase motors, the term “winding” usuallly refers to the complete set of all coils in a stator…. The stator winding.


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(2B)+(2B)' ?

 

[Evilsanta]

No just staying with the 3 phase motors for now as they are the most common ones we receive in and work on. I can do most of the work on the motors at present but it's looking into the stator and checking to see how many poles the motor has is where it ends. The guy training myself has said that it depends on the changes within, ie as one leg goes up and then down then that's a two pole. If it goes up, down, down then up its a 4 pole. It's trying to see what he sees is confusing to me, he draws the winding diagram out and I can follow it from there but I want to be able to draw the diagram myself from looking in and gathering the information myself so I can progress my learning. If anyone knows any good books or tips to help that would be great.

Thanks alan

 

[petronila]

Hi Evilsanta

Like pete sayd the poles depends of speed and frequency.

IMO you want to know how connect a winding to get a determinate pole number. This depends of experience and is a hard issue, so could be good that you play attention to your collegue and read some basic books or guides about winding motor. One excellent could be founded in

http://www.easa.com/software/HowToWindThreePhaseStators.

Regards

Carlos

 

[electricpete]

Assume typical lap winding.

The inter-coil jumpers within a group are the same for all groups. For example connect top lead of one coil to bottom lead of the next coil CW.

The polarity of physically adjacent coil groups must alternate (N/S/N/S etc). That must be considered in connecting the jumpers between poles. Assuming there is only one circuit per phase, the simplest way is adjacent pole connection. See here for that thread237-281260
The powerpoint attached there (adjacent pole) gives an idea of typical pole jumpers. When you look at those pole jumpers in the adjacent pole connection, you’ll see they go either top to top or bottom to bottom (they don’t go top to bottom or bottom to top for adjacent pole connection with short jumpers).

Lots of complications and variations possible. The groups in a phase are not always connected in one series path. Sometimes there are multiple parallel paths, per phase, each referred to as a “circuit”. A two-circuit winding has two parallels per phase.

If I were studying a winding, I would START with the nameplate to determine the nuimber of poles, then look at the winding itself to try to get additional details. There are plenty of the forum that spend a lot more time with windings than me.

I agree 100% with petronilla to get some good training. Unfortunately the site mentioned in the linked thread (uiitraining) no longer exists. I don’t know of any good free training materials. Maybe forum member zlatkodo has some info on his site? (if not, that might be a good marketing tool to get more people to your site… I’d link to it!). As far as books, Rosenberg’s book is often mentioned as a rewinder’s bible but it’s somewhat old and not laid out for beginners. EASA is the trade organization for motor shops in the US. You definitely can’t go wrong with their training materials if you can afford them.


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(2B)+(2B)' ?

 

[Evilsanta]

Thanks for the inputs guys its been most helpful, I can gauge the poles if theres a name plate easy enough its on the regular occurance that the nameplate has been broken off or perhaps the motor has been wound after manufacture to a different spec and the original name plate is still on the motor. Ive bought the book and in the process of downloading the file from the EASA website so fingers crossed there will be useful information on that.

Thanks Alan.

 

[zlatkodo]

The question is not as simple as it seems at first glance.
- In most cases, an experienced technician will immediately recognize the winding, thanks to previous experience.
- Some technicians are trying to determine the number of poles on the basis of winding pitch, but this way is quite unreliable. Here is one example: a 2 pole, single layer winding in 24 slots with pitch 1-8.
- Also, the so-called "polarity test" is not always reliable.
- What should be done? First, you should draw what you found and compare with previous diagrams. But, sometimes it is not helpful . For example: what is the number of poles for this simple three phase winding?

http://i58.tinypic.com/t80tva.png[/IMG]]
It's not so obvious that this winding is 10 pole.

In such a case, an analysis is only help. But note that analysis is time consuming task and may be performed manually ( hard task) or by means of a suitable software. Briefly on this is here:
(please find a title: Very basic question: In what way the number of poles should be determined?)
Link

BTW, Pete, thanks for your suggestion.

[URL unfurl="true"]http://winding.wix.com/design[/url]

 

[theode]

Assuming that the rotor can be taken out,a compass may be used.
Use a low voltage dc supply (enough to deflect the needle) across one phase.
Move the compass around the inside of the stator.
It will alternate north/south as you go round.
Do this for each phase.
n/s=2 pole n/s/n/s=4 pole and so on.

 

[Evilsanta]

Good thinking, had considered that but only problem with using dc power to pole check it is, if the winding is blew out on two phases then I won't be able to check it. I think experience is the way forward to be able to do it efficiently.