480Y 277 delta motor wiring

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Aleman

Senior Member
Location
Southern Ca, USA
We have a motor on a machine built for 480V and it is in a building that has only 208/120. It's European but the motor in question is rated for 60hz.
On the nameplate it states 480Y 277 Delta. It's a new one on me, usually I see motors that are wired one way (Y) for high voltage typically 480 and
the other way (Delta) for the low voltage 208. It's a 6 lead motor same as other IEC motors I have worked with. I was asked if this could be wired to run
on 208 and I said to buy a transformer. How can you get 3 phase to phase 277V without using neutral or ground? It's not my job but I am curious about
this one.
 

Smart $

Esteemed Member
Location
Ohio
We have a motor on a machine built for 480V and it is in a building that has only 208/120. It's European but the motor in question is rated for 60hz.
On the nameplate it states 480Y 277 Delta. It's a new one on me, usually I see motors that are wired one way (Y) for high voltage typically 480 and
the other way (Delta) for the low voltage 208. It's a 6 lead motor same as other IEC motors I have worked with. I was asked if this could be wired to run
on 208 and I said to buy a transformer. How can you get 3 phase to phase 277V without using neutral or ground? It's not my job but I am curious about
this one.
Umm 480 wye and 277 delta is the same thing... only the latter uses a neutral wire. Think about it... 480 wye is three windings with one end connected together and the other ends each connected to a respective line. Connect the 480/277 neutral to the three leads connected together and you have 277 delta.

Note motor windings are never really delta or wye. A better depiction though still not technically accurate is three arced (as in part of a circle, not the fault type :)), but separate windings occupying 120° of a circle and their line-connected leads brought out radially, while their connected leads go inward to center...
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
Umm 480 wye and 277 delta is the same thing... only the latter uses a neutral wire. Think about it... 480 wye is three windings with one end connected together and the other ends each connected to a respective line. Connect the 480/277 neutral to the three leads connected together and you have 277 delta.
I'm lost here. Are you saying you can hook up a three phase motor with four wires and that makes it run on 277V?
Note motor windings are never really delta or wye. A better depiction though still not technically accurate is three arced (as in part of a circle, not the fault type :)), but separate windings occupying 120° of a circle and their line-connected leads brought out radially, while their connected leads go inward to center...
If a motor is wound star 10, 11, 12 (U6, V6, W6) all tie together and tie to 1,2,3 (U1, V1, W1) for delta. Are you saying that dual voltage IEC motors are not wound this way?
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Often motors are designed to be connected either in wye or delta. A motor that has 277V coils could either be connected in wye, to a 480V source. Or the coils could be connected in delta to a 277V source.

If the motor is specified as being '480V wye 208V delta', that _probably_ means that the coils have been designed to work acceptably over the range of 208V to 277V, but that the 'optimal' operating point is someplace in between.

-Jon
 

Smart $

Esteemed Member
Location
Ohio
Where is this 277V source to be found in three phase? That is like getting 120V line to line from 208V.
480/277V 3Ø 4W Line to Neutral or it is derived from 480V 3Ø 3W by connecting the windings in wye with a floated neutral. The latter is actually the same connections as the former without the source neutral wire.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Where is this 277V source to be found in three phase? That is like getting 120V line to line from 208V.

I don't know if anyone uses 277V three phase anywhere.

All I am saying is that I would read that name-plate as meaning that the motor can be connected in wye or delta, and that it has 277V 'coils' (voltage across the two terminals of a single phase in that motor).

Normally in the US this motor would be connected in wye, and connected to a 480V supply.

My guess is that 277V three phase is even less common than 120V delta. (And yes, 120V delta is used, for some shipboard systems...and if you took a normal 480:208/120wye transformer and re-connected the secondary in delta you would get 120V delta. Generally this sort of re-connection is not possible because the wye is welded in place...)

Multi-terminal motors can often be connected in bizarre ways that would in theory work if you had a bizarre power source.

-Jon
 

Aleman

Senior Member
Location
Southern Ca, USA
Often motors are designed to be connected either in wye or delta. A motor that has 277V coils could either be connected in wye, to a 480V source. Or the coils could be connected in delta to a 277V source.

If the motor is specified as being '480V wye 208V delta', that _probably_ means that the coils have been designed to work acceptably over the range of 208V to 277V, but that the 'optimal' operating point is someplace in between.

-Jon

So....the motor might be fine if hooked up to 208V Delta same as most of the motors I have worked with? Because if it can run on 480Y then the windings should be roughly equivalent to
any other motor that can be wired for high Y or low Delta? I realize this might not be optimal at the lower voltage but why would this motor be different than a typical motor wound for 480?

Another issue here is the increase in load when wired to Delta. The wiring in the panel is rated for 480Y loads. Which brings me to the next question which is....if it was converted to 277 Delta by tying
neutral to the Y, does the current increase?
 

Besoeker

Senior Member
Location
UK
We have a motor on a machine built for 480V and it is in a building that has only 208/120. It's European but the motor in question is rated for 60hz.
On the nameplate it states 480Y 277 Delta.
Are you sure it's European? EU land is standard 400/230V and 50 Hz.
 
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kwired

Electron manager
Location
NE Nebraska
Besoeker's question is valid.

But whether it is European or not voltage ratio is same

400/230 = 480/277 = 415/240 = ~1.732

Same individual motor coils in either case see same voltage across them if connected in wye at the higher voltage as they see if connected in delta at the lower voltage.
 

Besoeker

Senior Member
Location
UK
Besoeker's question is valid.

But whether it is European or not voltage ratio is same

400/230 = 480/277 = 415/240 = ~1.732
No disagreement with that but it wasn't really my point.
I was asking the OP if he was sure the motor really came from Europe.
480/277/60Hz isn't used in Euroland.

The "harmonised" standard across EU member states is 400/230/50Hz
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Most likely this is a Bonfiglioli (assuming so, because you said Italy) IEC motor that was originally DESIGNED to be used at 400V 50Hz when connected in Wye, then 230V 50Hz when connected in Delta. When connected in Wye, the V/Hz ratio of the motor is 8:1 (400/50). If you apply 480V 60Hz to is, the V/Hz ratio is still 8:1, so the motor will put out rated torque all day, every day, no problem. It will of course turn 20% faster.

But when Bonfiglioli gets the motor listed and labeled in North America, they sell it as a 480V rated motor. Then, BECAUSE people here might THINK it can also be connected to 230V, they explicitly make the nameplate say "277V" if connected in Delta, that way they will think twice about connecting it to 240V 60Hz, which would make it burn up.

So technically the motor is rated 480Y, 277V Delta, but not because anyone can USE it at 277V 3 phase since that doesn't exist. It just says that so that you know you CANNOT use it at anything but 480V when connected to a 60Hz system.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
I don't know from motors, but what does 277V delta mean? Three phase, three wires (no neutral) with 277V phase to phase?
 
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