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Is The Motor Delta Or Wye & How To Test It?

03/15/2017 9:48 AM

We have several motors made in the USA (industrial floor-standing band saw, belt sander etc.).

They are labelled only "240v 60hz 3 phase" and don't say wye or delta.

How can i tell which they need? I think it matters because 240v L-L

delta is 240v L-ground and 240v L-L wye is 139v L-ground.

I assume they're all delta since that's a standard voltage in the USA.

But the difficult question is another motor labelled "480v 60 hz 3-phase."

How do I test if it needs 480v L-L delta or wye?

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#1

Re: Is the motor delta or wye & how to test it?

03/15/2017 10:32 AM

Have you held up a wye tester to it? LOL.

that can be revealed with some quick continuity checks between the wires present.

Google it, for a fair assessment of what you are holding to hold it to, or hold up to it.

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#2

Re: Is the motor delta or wye & how to test it?

03/15/2017 10:58 AM

Maybe this will help:

"How to Wire a 480V 3-Phase Motor"

http://goneoutdoors.com/wire-480v-3phase-motor-4464117.html

How many wires are coming out?

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#3

Re: Is the motor delta or wye & how to test it?

03/15/2017 11:00 AM

The biggest hint is the number of wiring nodes available. If there are only three nodes (and none are chassis) then that three phase motor must be wye wired.

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#4

Re: Is The Motor Delta Or Wye & How To Test It?

03/15/2017 11:11 AM

Redfred- AFAIK 3-wire delta is common (3 "nodes") and 4-wire wye is common (4 "nodes") not the other way around. Do I mis-understand something?

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#6
In reply to #4

Re: Is The Motor Delta Or Wye & How To Test It?

03/15/2017 11:14 AM

No, you got it exactly.

Instead of claiming a brain fart, I'll claim I was testing people.

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#7
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Re: Is The Motor Delta Or Wye & How To Test It?

03/15/2017 11:22 AM

Redfdred, u did the hardest thing in the world, admitting your not perfect :)

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#8
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Re: Is The Motor Delta Or Wye & How To Test It?

03/15/2017 11:27 AM

redfred IS a test.

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#10
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Re: Is The Motor Delta Or Wye & How To Test It?

03/15/2017 11:35 AM

Only some pass it.

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#5

Re: Is The Motor Delta Or Wye & How To Test It?

03/15/2017 11:12 AM

They don't need to be either. As long as they get the correct voltage they are fine.

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#14
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Re: Is The Motor Delta Or Wye & How To Test It?

03/15/2017 6:50 PM

BINGO!

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#9

Re: Is The Motor Delta Or Wye & How To Test It?

03/15/2017 11:34 AM

It really isn't difficult to note down the serial number and manufacturer of each motor, and the manufacturers, now, is it?

<sigh>

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#11

Re: Is The Motor Delta Or Wye & How To Test It?

03/15/2017 11:47 AM

<...240v L-L delta is 240v L-ground and 240v L-L wye is 139v L-ground...> That statement is incorrect. The voltage between supply phase/live and ground/earth does not alter according to whether the motor windings are configured wye/star or delta; it is the voltage across each individual winding that alters.

What do the "as built" wiring schematic drawings say in each case? Have they been mislaid?

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#12
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Re: Is The Motor Delta Or Wye & How To Test It?

03/15/2017 11:59 AM

PWSlack, there are no as-builts or any paperwork, these motors were purchase by others. What I was trying to say is: 240 delta is 240 L-L and L-ground which is common in the USA 240 star or wye is 240 L-L, 240/(sq rt of 3) = 139v L-ground which afaik doesnt exist or is very uncommon

so doesnt it make a difference to the motor, most people say no!

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#13

Re: Is The Motor Delta Or Wye & How To Test It?

03/15/2017 5:19 PM

Apples and oranges.

How the motor coils are connected internally is not at all related to how the supply transformer is connected. If a motor says 240V, that means 240V phase to phase. If you have a 240V 3 phase system, it is 240V phase to phase. That's all you need to know. The phase to ground voltage reference of your supply is relevant to a number of other issues, but the connection to a 3 phase motor is NOT one of them.

The INTERNAL connection of the coils inside of the motor makes a difference ONLY to the motor design engineer, having to do with conductor dimensions, slot depth, and magnetic permeability of the steel.

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#15
In reply to #13

Re: Is The Motor Delta Or Wye & How To Test It?

03/16/2017 6:28 PM

I don't follow that. If the nameplate says 240V and there are just 3 studs in the box, there's no choice but to wire to them. Assuming you can't see inside the motor, you don't know whether the internal windings are Y or Δ, and it doesn't matter.

But if there are 6 studs and the nameplate doesn't say, it could be 240V Δ (415V Y), or 240V Y (139V Δ). Unless I'm missing something.

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#16

Re: Is The Motor Delta Or Wye & How To Test It?

03/16/2017 10:30 PM

Codemaster said: "But if there are 6 studs and the nameplate doesn't say, it could be 240V Δ (415V Y), or 240V Y (139V Δ). Unless I'm missing something." .......I think Codemaster meant to say: "it could be 240v delta (240 phase to phase and 240v line) or 139/240 wye or 240/415 wye." .......but what JRaef said, and makes the most sense to me is this: Motors always give the phase to phase voltage, not line to line, so 240v 3 phase means 240v phase to phase. .......also think about this: 139v phase to ground doesnt exist as a standard voltage. and so that leaves only 1 choice: 240v delta, and that is a standard voltage 60hz in the USA, in residential one phase is center tapped giving a house 120/240

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#17
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Re: Is The Motor Delta Or Wye & How To Test It?

03/17/2017 7:40 AM

I think we can all agree that the supply voltage is always quoted as line-line.

Can you confirm your supply voltage? Your original post implies 240V, but it's not entirely clear (to me anyway), and that would be 139V phase (or line) to neutral (or ground) which you say (correctly) doesn't exist as a standard voltage.

Also how many studs does your terminal box have?

Most motor nameplates nowadays state volts for Δ and Y, eg 400V Δ, 690V Y in Europe. Assuming, following JRaef, that if only one voltage is given it is always phase-phase, and your supply is 240V, the answer is clear - connect it in Δ.

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#18

Re: Is The Motor Delta Or Wye & How To Test It?

03/17/2017 1:31 PM

It does not matter what the source vector group is anymore than it matters how the motor is wired internally; the only requirement is that the line to line voltage from the source side match the terminal voltage listed on the load's nameplate. This assumes that both are of the same frequency, and that the shaft rotates in the desired direction; if not simply reverse two leads and proceed.

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1capybara (4); Brave Sir Robin (1); Codemaster (2); James Stewart (2); JRaef (1); PWSlack (2); RAMConsult (1); redfred (3); Rixter (1); tcmtech (1)

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