Motor Wiring

[Mumbaigirl]

We have an issue here on site. Our current electrical configuration at the site is Delta however we have recently purchased a few motors that could either be wired Y or Delta. The one that I am specifially asking about has 480 Y on the nameplate (Nameplate picture attached). From what I understand, if we wire it for Y configuration the amp draw would be less vs wiring it as a delta? Do we have to wire this motor as a Y? Or can we wire it as Delta without creating issues?

Thank you,
Jui

 

[LarryFine]

If the motor has only three wires or terminals, it does not matter whether the source is wye or delta.

If it has a neutral wire or terminal (which is very unusual), then the supply should be wye.

I would like to see the nameplate picture before commenting further.

 

[Mumbaigirl]

If the motor has only three wires or terminals, it does not matter whether the source is wye or delta.

If it has a neutral wire or terminal (which is very unusual), then the supply should be wye.

I would like to see the nameplate picture before commenting further.

Thank you so much Larry. I am attaching the nameplate picture.

 

[LarryFine]

Okay, I see the "480 Y" under V, but that's more of a reference than a requirement.

This motor will function perfectly fine on 480v whether the source is wye or delta.

As a side note, I don't understand why T3 has a different number in the far right column.

 

[Jraef]

In an IEC motor design, “dual voltage” motors are made to be connected in Wye for the higher voltage, Delta for the lower voltage, because the intent is for 50Hz countries that use 400Y230V nominal systems.

But when the same companies make a motor suited for use in North Anerica where we use 480V 60Hz, a motor designed for 400V 50Hz will work fine, because the ratio of voltage and frequency is the same (or close enough); 400/50 = 8:1, and 480/60 = 8:1.

But that same motor CANNOT be effectively used in N. America at 240V 60Hz, because the ratio is off by too much. 230/50 = 4.6:1, 240/60 = 4:1, so it is lower by more than 10% and will make the motor run hot and fail prematurely.

So the label put on the motor for use in N.America, will ONLY list the Wye connection as valid for connection to a 480V system. Inside the connection box, the diagram might show both possibilities, as this one does, but you must ONLY use the Wye connection.

Whether your line source is Wye or Delta has zero bearing on this issue. The motor doesn’t “know or care”, it only is concerned with the voltage and frequency applied to it.

 

[Mumbaigirl]

Thank you so much! This helps.

Just so I understand, is there something in the nameplate that made you say the Y is for reference only and that the motor could be wired either delta or wye?

Also, I do not know why the number for T3 is different.

 

[LarryFine]

Disclaimer: The second pic was not posted when I made my comments.

 

[Mumbaigirl]

Thank you so much Jraef and Larry! Your explanation has been very helpful.

Why would the diagram show wiring for both Delta and Wye if it's recommended to be wired as a wye? Just for my future reference!

 

[Jraef]

Because that sticker on the inside of the cover is on every motor they sell, regardless of where it goes. The engraved nameplate on the outside is the only thing that changes.

 

[LarryFine]

Why would the diagram show wiring for both Delta and Wye if it's recommended to be wired as a wye?

In my opinion, it's wired as a delta, because there is no neutral terminal.

If anything, the Y merely indicates that it expects the source to be a wye.

 

[don_resqcapt19]

In my opinion, it's wired as a delta, because there is no neutral terminal.

If anything, the Y merely indicates that it expects the source to be a wye.

There is no reason a motor would care if the source is a wye or delta. It only cares about the line to line voltage,
I have never seen a 3 phase motor with a neutral connection. No idea what that would be for?

 

[MD Automation]

There is no reason a motor would care if the source is a wye or delta. It only cares about the line to line voltage,

Absolutely! I see a lot of confusion about this on this forum at times - the (incorrect) thinking that a dual voltage IEC motor capable of being wired as Wye (Hi voltage) or Delta (Low voltage) must be configured to match the Mains source supply (Wye or Delta). They are completely independent of each other. As Don points out, the motor just cares about the (3) L-L voltages. Not how they were derived.

Think about it this way - the single most common step down transformer is a 480 Delta -> 208 Wye. And it's quite common to have facility Mains of 480/277 Wye feeding that transformer's 480 Delta primary. So (source) Wye feeding a (load) Delta. The primary Delta windings on the transformer don't care about the Wye source configuration. Just that the L-L voltage is correct.

Same for motors - and after all, induction motors are kissing cousins to transformers! An induction motor is just like a transformer whose secondary can rotate... and (hopefully) is not shorted

Because that sticker on the inside of the cover is on every motor they sell, regardless of where it goes. The engraved nameplate on the outside is the only thing that changes.

Also absolutely! Because it is possible to configure the motor in one of 2 ways, the sticker is on the inside so the end user can verify the shorting jumpers are configured correctly. Just in case somebody ever disconnected them, or they were delivered wrong from the factory (rare, but it happens).

The nameplate riveted to the front, as Jraef points out, is for the end user that ordered it and here it's telling you to connect the jumpers as Wye and run it on 480 VAC only.