Delta vs Wye motor connections

[mull982]

I have been reading informatino regarding delta vs wye motor configurations but am still a little foggy on the subject. I have noticed that most of the motors in our plant are wired for a 3-wire delta configuration. If I understand correctly, a 3-wire connection is not one that can be changed, and it is what it is wheather its delta or wye.

This brings me to the 6-wire motors which can be changed between delta and wye. I understand that a delta wired motor will have the L-L line voltage across the stator windings, and a wye configured motor will have (L-L)/1.73V across the stator windings. I've seen a high voltage and low voltage referenced when using delta / wye connectiosn but am unsure what these voltages refer to? If I have a 480V L-L system voltage, would this be a high voltage or low voltage when refering it to a 480V 6-wire motor? What is meant by these voltages.

Aside from a wye-start / delta-run soft starting application what are some other applications where a motor would be wired for a wye configuration for starting and running? What happens if you wire a motor configured for one type the other way?

I would appreciate any info or resources regarding this topic.

 

[coulter]

mull -
It's too much for me to tackle all at once. i'll nibble off a couple of pieces

...Aside from a wye-start / delta-run soft starting application what are some other applications where a motor would be wired for a wye configuration for starting and running? ...

I'm not much on motor winding theory. But there are plenty of wye wound motors out there. When I was fingering the wires for a living, that is pretty much all I saw. 99% fell into 2 - 50hp, 9 lead dual voltage. I don't know what is common now.

... What happens if you wire a motor configured for one type the other way? ...

If you connect a delta wound motor as a wye, it is a lower hp motor.

If you connect a wye wound motor as a delta -- well, I've never seen one that you could do that to. All of the wye wound motors I've seen are 9 lead or 3 lead. The 9 lead are dual voltage (usually 480/240) and the 3 lead are single voltage. The 3 lead have the wye point buried in the internals. The 9 lead has 6 coils that can be connected in series, or parallel fed. One set of three windings have the wye point already made up and buried in the internals

carl

 

[Jraef]

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.

 

[coulter]

... "9 lead motors" can be either Dual Voltage Wye or Dual Voltage Delta (again, you won't know the difference), typically 230/460V. ...

This confused non-Southern American is completely unsure how the motor coils of a dual voltage, 9 lead motor could be connected delta. All the ones I have seen have LV with 3 pairs individually connected to line and one trio connected. The HV connection is 3 pairs connected, and 3 leads to line. That sure looks like there is a wye point buried in the motor.

Perhaps you could send a sketch on how the coils of a dual voltage, 9 lead motor are connected for an internal delta.

carl

 

[crossman]

Carl, they do make a nine lead, dual voltage, delta motor. Give me a few minutes and I'll draw the diagram amd post it.

 

[crossman]

Here is what the windings and connections of the nine-lead, dual-voltage, delta motor look like.

The high voltage connection is straight-forward. The low voltage connection isn't quite so obvious.

Also, it is easy to tell whether one is working with a wye 9-lead or delta 9-lead by using an ohmeter to check the common leads.

 

[coulter]

Carl, they do make a nine lead, dual voltage, delta motor. Give me a few minutes and I'll draw the diagram amd post it.

I saw this picture in a 1934 motor winding handbook. but it looked like this. But, I have never seen or heard of one - and I have wired a lot (until twenty-five years ago). Is this something that has been around and common for ever, or a recent (less than twenty-five years) development, or a 1934 design that never went anywhere?

carl

 

[crossman]

Good question Carl. I can't say that I ever actually hooked up or even saw a motor that was wound like this. I have only seen it mentioned in the texts. I would bet that they made these years ago but don't anymore. I am on dial-up right now, otherwise I would do a search.

 

[mivey]

Carl, your picture looks like the 1/2 voltage version of crossman's picture.
see:
http://www.usmotors.com/products/ProFacts/1-120-7.htm

 

[Jraef]

Here is what the windings and connections of the nine-lead, dual-voltage, delta motor look like.

The high voltage connection is straight-forward. The low voltage connection isn't quite so obvious.

Also, it is easy to tell whether one is working with a wye 9-lead or delta 9-lead by using an ohmeter to check the common leads.

That's the right diagram, I saw a lot of them when I worked in a surplus house years ago, no idea if anyone still makes or sells them.

The connections are:
LV: L1 to 1, 6 & 7; L2 to 2, 4, &8; L3 to 3, 5 &9
HV: Li to 1, L2 to 2, L3 to 3, Join 4 & 7, 5 & 8, 6 & 9

 

[coulter]

Carl, your picture looks like the 1/2 voltage version of crossman's picture. ...

Yes,as you saw, they are the same. Just grab the corners and stretch it out to the HV version.

carl

 

[frenchelectrican]

I will add a link to the motor connection diagram as well http://www.electricmotorwarehouse.com/motor_connection_diagrams.htm

this will be pretty instering combation you may run into one of the days

Merci,Marc

 

[mull982]

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. .

Looking through some datasheets here at the plant I noticed that we have both 480V 3-wire delta and 480V 3-wire wye motors. Our system voltage is 480V. Basically what you are saying is as long as the motor is rated for 480V we should not care weather we install a delta or wye motor on our system? If we installed a 3-wire wye motor on our 480V system would the motor only see 277V and thus only give 1/3hp as you explained?

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.

So if I have a 6-lead 480V motor that I want to put on my system I have an option of how I connect this motor either wye or delta? What do you mean when you say "you wont know the difference" regarding the wye or delta windings? With 6 leads, dont you have the option of wiring a motor for wye or delta? On my 480V system I'm guessing I want to wire this motor for delta? What would happen if i wired it in the wye configuration, would I only have 277V on the motor and thus only 1/3hp? Would I want to use the wye configuration if I only had a 277V system voltage?

 

[don_resqcapt19]

Our system voltage is 480V. Basically what you are saying is as long as the motor is rated for 480V we should not care weather we install a delta or wye motor on our system? If we installed a 3-wire wye motor on our 480V system would the motor only see 277V and thus only give 1/3hp as you explained?

If the motor is designed for 480 volts and the windings connected correctly, it will give the full rated horsepower. You are correct that in a wye motor each internal coil (or set of two coils in series for a dual volatage motor) will only have 277 volts across it, however that is what it is designed to run on. Each coil or set of coils in a delta wound motor is designed for 480 volts.

So if I have a 6-lead 480V motor that I want to put on my system I have an option of how I connect this motor either wye or delta?

That motor would be designded for wye start and delta run. You don't really have a choice.[/quote]

On my 480V system I'm guessing I want to wire this motor for delta? What would happen if i wired it in the wye configuration, would I only have 277V on the motor and thus only 1/3hp? Would I want to use the wye configuration if I only had a 277V system voltage?

I am not aware of any 3 phase 277 volt systems so you have to supply it with 480 and connect it for delta.

 

[LarryFine]

The high voltage connection is straight-forward. The low voltage connection isn't quite so obvious.

It would be if you look at it like this: Mentally "pick up" the three L's (the little "open Deltas") above, and move them towards the center of the triangle, so the pairs of coils overlap, literally placing them in parallel. You'd have T6 and T7 meeting at T1, T9 and T5 meeting at T3, and T4 and T8 meeting at T2.

Looking at one side of the large triangle, say T1 to T4 and T7 to T2, each pair of windings can be in series or in parallel; in series for high volts, or in parallel for low volts. Either way, each winding receives its design voltage, thus current, thus power, thus its contribution to output horsepower.

Similar to dual-voltage transformer windings, like buck-boosts.


Added: Carl's drawing shows the 'after' positions of what I described above: http://forums.mikeholt.com/attachment.php?attachmentid=1525&d=1208219067

 

[rattus]

Obvious:

Obvious:

Obviously, you can wire the split windings in series or in parallel. Same flux, same coil currents, twice the line current at half the voltage.

 

[crossman]

When I said "the low voltage connection isn't quite so obvious" I wasn't implying that I didn't know how to do it. :roll: I was just saying "it isn't quite so obvious as the high voltage connection."

One way to look at the low voltage connection is that we are creating three open deltas.... not that we actually are, but going from my diagram, the LV connection would appear to be three open deltas.

 

[LarryFine]

So if I have a 6-lead 480V motor that I want to put on my system I have an option of how I connect this motor either wye or delta?

No, if you have a 6-lead 480v motor, you have the option of 240v or 480v, but it will remain wye or delta. A 9-lead motor is actually a 12-lead motor with one connection point inaccessible.

To switch a motor between wye and delta, you need all of the winding ends individually accessible, which means it will be a 6-lead, single-voltage motor, or a 12-lead, dual-voltage motor.

 

[crossman]

No, if you have a 6-lead 480v motor, you have the option of 240v or 480v

I am missing something here. Can a six lead 480v motor also be connected for 240 volts?

 

[billsnuff]

Connections

Connections

here is a bunch of motor connection dwgs i ran across awhile back

http://www.usmotors.com/Connections/Connections.htm

enjoy