# Delta Wiring Scheme



## modern_messiah (Dec 8, 2010)

Hi all,

I need some help determining the correct winding pattern and end configuration for a motor I’m building. This is the _first_ time I’ve ever attempted this so I want to try and get it right without too many issues.

My motor has an 8 pole, 9 tooth configuration and I have decided to try and use the delta wiring scheme. Everything I know (so not much) is here:

http://www.bavaria-direct.co.za/models/images/CD_Delta_diagram.gif

As I understand it, this diagram implies that:

- The start of phase 1 connects to the end of phase 3
- The start of phase 3 connects to the end of phase 2
- The start of phase 2 connects to the end of phase 1


Is the winding diagram below (the winding configuration and delta connections) correct? Those 3 endpoints labelled at Phase 1/2/3 connect to the 3 phase output of the controller yes?




So yeah – just after someone to stop me before I do something dumb. Your guidance would be greatly appreciated!

Cheers,

- Matt


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## DawidvC (Feb 14, 2010)

It looks correct in that each winding start and end appropriately. It is, however, not a good idea to run in delta, as you can have unwanted circulating current in the motor. It would be preferable to, at least for testing purposes, run the motor in a star configuration.

Dawid


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## frodus (Apr 12, 2008)

you mean "Wye" configuration.


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## Jorge Garcia (Apr 8, 2011)

frodus said:


> you mean "Wye" configuration.


Aren't "wye" and "star" configurations both the same thing? I have thought so for so long. Maybe have been wrong all this time.


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## Tesseract (Sep 27, 2008)

frodus said:


> you mean "Wye" configuration.


The rest of the world (ie - besides the US) calls it "star". Only we call it "wye".


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## frodus (Apr 12, 2008)

yeah, just found that.... sorry for the correction.... In communications and lighting controls (my field) Star is used for a bunch of points coming from one place, and we use WYE or Delta for wiring power. I had never heard of Star before concerning a motor, appologies.


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## modern_messiah (Dec 8, 2010)

For the same number of turns and wire thickness:

DELTA gives 1.73 higher power and amp draw than STAR

DELTA RPM (Kv) = 1.73 higher than STAR Kv 

DELTA Kt (Torque) = 1.73 lower lower than STAR Kt

In a STAR connection, 1.732 less turns are needed to be wound to get the same power as a DELTA connected motor.

So I guess STAR (WYE) would be better in a small motor because you need less turns for the same power, but you will have a lower possible RPM. When the motor is capabale of RPMs higher than you'd ever reasonably need then I guess it doesn't matter so much...

HOWEVER! Your statement that there would be "unwanted circulating current in the motor" confuses me because a WYE configuration simply has the end points of each phase connected (see here:http://www.powercroco.de/bewicklungsrechner.html).

So won't the same thing happen? Or is this occurring in the DELTA config because the end points of each phase connect to the start point of other phases and hence will be sending currents through windings/coils that shouldn't be powered at that time and hence causing 'mis-firing' (hope that makes sense)? 

I don't have a firm grasp on the situation obviously.


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## Jorge Garcia (Apr 8, 2011)

Perhaps another advantage (or maybe just a difference) between a delta and a star configuration would be the capability of a delta connection to deal with fault lines. Delta configurations are more "reliable" than star connections in this regards.

However, a star configuration can be somewhat protected in a similar way by pulling a fourth line from the star center. A neutral line, that is.


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## DawidvC (Feb 14, 2010)

modern_messiah said:


> HOWEVER! Your statement that there would be "unwanted circulating current in the motor" confuses me because a WYE configuration simply has the end points of each phase connected (see here:http://www.powercroco.de/bewicklungsrechner.html).
> 
> So won't the same thing happen? Or is this occurring in the DELTA config because the end points of each phase connect to the start point of other phases and hence will be sending currents through windings/coils that shouldn't be powered at that time and hence causing 'mis-firing' (hope that makes sense)?
> 
> I don't have a firm grasp on the situation obviously.


In an untested motor, as in this new design, you can end up with different coil impedances, changing the current for each phase slightly. In an industrial motor it doesn't matter too much, but any invertor-driven motor *may* create a problemif the phases are in delta and they are far enough out. A wye-connection is simply less sensitive to phase imbalance in the motor, and is less likely to create unwanted circulating currents in the stator and rotor. If you take a look at the two different schemes you will see that delta allows more current to flow, and also can allow circulating currents, which can lead to problems.

I was not suggesting that delta not be used at all. My suggestion was that initial testing be done with the motor connected in wye, so that it is easier to troubleshoot any problems. If the phases are in reasonable balance ( < 1% imbalance), you can run it any way you please.

Regards
Dawid


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## modern_messiah (Dec 8, 2010)

Great explanation Dawid...that's cleared a lot of thing's up for me. I guess the best way to build my motor in this case would be to cut identical lengths of wire and use them to wind the teeth, and not just wind the same number of turns irrespective of how much wire I use?

Either way I think I'll go with the WYE/STAR connection regardless, because a smaller number of turns is desirable in my design - it just didn't occur to me until I was forced to think about it a bit harder by responses in this thread.

Thanks!


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## DawidvC (Feb 14, 2010)

My pleasure to have been of help.


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