# Delta-wye motor



## Jirishno1 (Feb 6, 2014)

We had a problem with a motor that can be hooked-up wye or delta by changing links in the peckerhead. The Siemens breaker that was part of the contractor kept tripping. As it turned out the breaker was to small,so we increased the size but the breaker still tripped when it was hooked up delta,when we hooked up wye the breaker held and motor worked fine. Can't figure out what the difference was!


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## Big John (May 23, 2010)

The Δ connection means that full phase-to-phase voltage is imposed across each winding. 

The Y connection means that any two windings are in series, and phase-to-phase voltage is divided between them. There's a higher total winding impedance so for the same voltage you would get a lower current.

But it's not just a matter of preference, changing the winding configuration changes the voltage the motor is designed to run on and it's very likely listed on the nameplate as dual voltage, e.g.: 208/480


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## don_resqcapt19 (Jul 18, 2010)

Big John said:


> ...
> 
> But it's not just a matter of preference, changing the winding configuration changes the voltage the motor is designed to run on and it's very likely listed on the nameplate as dual voltage, e.g.: 208/480


That would not be the correct voltages for a delta/wye dual voltage motor. If the 208 is correct the high voltage would be ~360 and if the 480 is correct the low would be 277.


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## Safari (Jul 9, 2013)

Jirishno1 said:


> We had a problem with a motor that can be hooked-up wye or delta by changing links in the peckerhead. The Siemens breaker that was part of the contractor kept tripping. As it turned out the breaker was to small,so we increased the size but the breaker still tripped when it was hooked up delta,when we hooked up wye the breaker held and motor worked fine. Can't figure out what the difference was!


in wye line current is same as phase current while in Delta line current is root three of phase current. so obviously your breaker would trip on Delta.wish you used a clamp meter to get the currents. also state the size of breaker.
AND
not all motors can run in Delta.check the motor name plate.

Sent from my HUAWEI Y210-0100 using Tapatalk 2


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## Ultrafault (Dec 16, 2012)

I have stolen this verbatim from our dear friend jreaf for you.

Assuming you are in North America, don't get hung up on the "Delta vs Wye" winding issue, it is almost completely irrelevant. A NEMA designed motor is what it is, you usually have no way of knowing, short of dissection, whether it is wound in Delta or Wye internally, nor should you care.

Don't confuse this with Delta or Wye power systems, the issues are completely separate and not related as far as functionality goes. Aside from Y-Start / Delta-Run motors, you ALWAYS only run 3 leads to the motor, NEVER the 4th (neutral). So how it is connected internally is for the motor mfr. to worry about, not you.

In a Wye-Start / Delta Run motor, the windings, and associated power ratings, are still based on the Delta configuration. But when you bring all of the motor leads out to the connection box and connect them in Wye, you get the 1.73 reduction factor (58%) on effective voltage across the windings. Since torque, and therefore current, follow the square of the applied voltage, you also get 33% (.58 x .58) of the normal torque and current. Since the frequency didn't change and you have less torque, you have less HP by the same ratio, so your shaft HP is down to 33% as well. Technically then, you could run a motor in Wye continuously is you are ABSOLUTELY sure the mechanical load on it is never more than 1/3 of its rating (although you must as "Why?")

How that relates to "Leads" in single speed NEMA motors is as follows:
"6 lead motors" are either single voltage motors, Wye or Delta wound (you won't know the difference) or they are single voltage, Wye-Dela start. They can also be dual-windings, for instance as you would use with a Part Winding starter. In some RARE instances they are dual voltage motors, but the voltage ratio is always 1.732:1, so that would be 480/277V or 575/331V; you won't see a lot of those, not worth considering.

"9 lead motors" can be either Dual Voltage Wye or Dual Voltage Delta (again, you won't know the difference), typically 230/460V. They CANNOT be connected for Wye-start / Delta Run. In some rare cases you will see IEC motors sold in N. America as Single Voltage 9 lead motors, because they base it only on the high voltage connection (Wye only).

"12 lead motors" are where you get into all kinds of possibilities, i.e. dual voltage, Wye-Delta starting or pretty much any lower configuration mentioned above.

In the IEC motor world, more specifically Great Britain (and Australia / New Zealand), THEY use Delta or Wye winding configurations for voltage changing. A 380/220V motor is connected with its windings in "Star" (Wye) for 380V line supply, Delta for 220V (380 / 1.732 = 220). Their system essentially rates the motor based on the Delta configuration as well, but because you are changing the applied voltage, the power remains the same. We don't do that here in the US because we don't have the same ratios of voltage supplies. 

Good aint it.


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## Big John (May 23, 2010)

don_resqcapt19 said:


> That would not be the correct voltages for a delta/wye dual voltage motor. If the 208 is correct the high voltage would be ~360 and if the 480 is correct the low would be 277.


 Good catch. Brain fart.


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