# Can a three phase motor wired in wye be rewired for delta?



## MDR-Maker (Apr 18, 2018)

I have a surface grinder who's motor is wired in wye.

I need to install a three phase converter to make it run, both spindle motor and the hydraulic pump motor.

Reading through American Rotary's PAC are wired in delta and according to their tech folks I need a transformer(?) that will change the delta feed to wye. At about $700 I wanted to know if there is a less expensive route I can take.

The Doerr 1hp spindle motor has 9 leads and based on my research is wired in wye with leads 4,5,6 tied together. 

Any help would be appreciated.

Thanks


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## ddickey (Apr 18, 2018)

Is this a dual voltage motor?


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## markba633csi (Apr 18, 2018)

I thought 9 wire motors could be wired either way? 
Mark


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## MDR-Maker (Apr 18, 2018)

ddickey said:


> Is this a dual voltage motor?




To the best of knowledge it is.

Based on the wiring of the leads it's 220 volts. The motor plate shows it can be wired for 440.

I'm still trying to get more information on the motor. The model number is:67314GD801.


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## markba633csi (Apr 18, 2018)

Correct me if I'm wrong but I think the delta connection is the lower voltage and the wye (or "star") is the higher-?
Can you post a pic of the motor plate?
Mark
ps I'm wrong it looks like the delta is the higher


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## Martin W (Apr 18, 2018)

Not sure if this helps. http://www.phaseconverterinfo.com/phaseconverter_deltawye.htm 
Cheers
Martin


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## Bi11Hudson (Apr 18, 2018)

The spindle motor appears to be wired for low (240) volts. A nine wire motor with 4,5,6 tied together is the pointer there. It is "Wye" connected. To convert to delta, it would be necessary to physically enter the motor and access the (theoretical) 10, 11, 12 connections. They are connected internally and not easily accessable. And not so easily changed, even if you knew how to rewind a motor. *Can be done*(?) but then you have to deal with winding voltage ratings. One divided by the square root of three is your starting point there. Or the inverse of*........*

Then there is the pump(?) motor, already wound in delta. Likely a 12 wire motor, or a 6 wire *fixed voltage* motor. There wasn't much detail given for that one. Lacking that, I would have to ask*:*

What voltage did the machine run on before purchase? 240 *or* 480? In any case, there is no need to change the motor from one to the other. Just get the voltage right and go. Again, 240 or 480.....

The 3 phase conversion has two solutions. A rotary converter is nothing more than a 3 phase motor with a few capacitors and a kicker to start it. The electronic converter *synthesizes* a three phase output. It is not a pure sine wave but usable in motor(and other such) applications. Just don't run a transformer on it without derating it.

There *should be* no plausable need to switch a motor from wye to delta to make it work. Just hook it up for whichever voltage. If there is a passage in the converter instructions about a motor being wye or delta, I would take a long, hard look at the converter itself, not the motors. No, I don't have one. But I have worked with motors since 1969. And yet to let the majic smoke out.

Bill Hudson​[Edit] The connections I saw on the converter manufacturer page are relative only to how 120 volts are derived. As long as this device is used only for three phase loads, there is no concern. The assumption that you will be connected to a 120-240 single phase source, such as a shop sub-main, with multiple circuit breakers. If there are any 120 volt loads connected to the converter, just watch out for the "wild leg".


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## markba633csi (Apr 19, 2018)

Apparently this is a dual voltage motor and they do bring out all the necessary taps-
Waiting on a picture of the motor nameplate to see
Mark


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## mksj (Apr 19, 2018)

The restriction regarding RPCs is when the motor Y is tied to neutral/ground. If the Y is not tied to neutral/ground, it should be a non-issue. You need to provide the motor plate/wiring or check the schematic, but. most motors do not have a Y star ground/neutral, T4-6 are just connect together. This is one reason why when measuring RPC voltages you look at leg to leg not leg to ground for balancing the voltages.



Per the blurb:
*If a piece of three-phase equipment operates only on phase-to-phase voltages, it does not matter whether the power is configured as wye or as delta. If none of the circuits in the machine or the motor being operated derive a voltage by referencing neutral/ground, the machine does not know or care where ground/neutral is in reference to any of the phases*. It only “sees” the relationship between the phases. It is evident that if you reference the three voltages of wye power and “erase” the connection to ground/neutral, you have a triangle, the same as in delta configured power. Only when equipment has single-phase 120V circuits that are derived from phase-to-neutral connections does it matter if the power is configured as wye or delta.

If the three-phase equipment has 120V phase-to-neutral circuits that cannot be isolated and connected to either leg 1 or leg 2, the output of the phase converter must be passed through a 240V delta to 120/208V wye isolation transformer. This transformer will establish ground and neutral at equal distance from all three legs and deliver the power in a wye configuration.


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## MDR-Maker (Apr 19, 2018)

markba633csi said:


> Correct me if I'm wrong but I think the delta connection is the lower voltage and the wye (or "star") is the higher-?
> Can you post a pic of the motor plate?
> Mark
> ps I'm wrong it looks like the delta is the higher





markba633csi said:


> Correct me if I'm wrong but I think the delta connection is the lower voltage and the wye (or "star") is the higher-?
> Can you post a pic of the motor plate?
> Mark
> ps I'm wrong it looks like the delta is the higher





markba633csi said:


> Correct me if I'm wrong but I think the delta connection is the lower voltage and the wye (or "star") is the higher-?
> Can you post a pic of the motor plate?
> Mark
> ps I'm wrong it looks like the delta is the higher





markba633csi said:


> Apparently this is a dual voltage motor and they do bring out all the necessary taps-
> Waiting on a picture of the motor nameplate to see
> Mark




Mark, here is a picture of the motor plate.


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## MDR-Maker (Apr 19, 2018)

Martin W said:


> Not sure if this helps. http://www.phaseconverterinfo.com/phaseconverter_deltawye.htm
> Cheers
> Martin



Thanks for the reference Martin.

I've read it a couple of times - sometimes my bulb doesn't burn very brightly.

It was very helpful.


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## MDR-Maker (Apr 19, 2018)

Thanks to everyone that has helped me out on this.

The surface grinder has three motor systems, the spindle motor wired in 208/220, the hydraulic pump motor wired 220, and the lube pump motor. I finally found the motor tag for the lube pump  which after a bunch of cleaning showed it to be wired for 208. 

Now that I know there are no 120 volt systems in the machine , and after all  the information you all provided, I feel a lot more comfortable with the RPC route.


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## Joe in Oz (Apr 19, 2018)

Hi. This motor can easily be changed from 415-440 Wye (or Y) connection to Delta 208-230V. Just look at google photos for determining which pairs of wires need to be joined. Hint: in Y mode, there are 3 single wires to be connected to the supply, with the other 3 connected each other only.
Another hint: very often the terminal arrangements are pasted on the INSIDE of the terminal box lid - and you are worrying much more than necessary 
 I'm a bit puzzled by the "9 wire" comment. There are three sets of coils with two ends each in the motor - that makes 6. Or did you count the 3 wires for the power GOING IN?
Also, your pump motor may only have 3 wires in the terminal box. If so, the other 3 are joined to each other internally, which means you may need to open up the motor and find that soldered or welded joint, to bring those 3 wires out into the junction box too. Sometimes that is very easy (in fact I have seen that joint made and hidden INSIDE the junction box - which makes it very easy.
On the other hand, if there are already 3 pairs of wires terminated in the terminal box, and the motor labelled 400/414/440V, then it is already in delta mode - and that is the lowest voltage it will provide the maximum power. SO you might be stuck. However, it is still worth trying that motor on 220V 3-phase, because you may not NEED the rated motor power to pump what you need. Never give up too easily  
I've converted loads of motors that others had given up on.... If you need more detailed help, take a nice sharp photo of the terminal box with the lid off both motors. 
If finding the "star point" joint inside the motor is required, don't despair: take that motor apart and show us a few photos of the stator end with all the insulating sleeves. Chances are high that I can find it for you in a photo.


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## MDR-Maker (Apr 19, 2018)

Thanks Joe.

With leads 4, 5, and 6 tied together I believe I'm looking at a 220 volt wired motor in wye configuration.

If it were high voltage I believe that leads 4 and 7, 5 and 8, and 6 and 9 would be tied together.

This counts the line wires, 3 line and 6 leads from the motor.

This is what I understand from what folks have given me for information.


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## Martin W (Apr 19, 2018)

I have a 440 volt motor wired delta, that I run on 240 volt three phase for 10 years now. I see no noticeable loss of power or any heat generated. This is on a 29 spindle boring machine for wood. Saved having it rewound because it was a very compact motor.
Cheers
Martin


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## MDR-Maker (Apr 20, 2018)

Another question.

Is anyone running a surface grinder, having the three motor systems I referenced earlier, on anything less than an extreme duty 5hp level converter? I've been told by one company that I should use this level converter yet another says that the system will run fine on the base level 3hp.

The system has a 1hp spindle motor, a 1/2hp hydraulic pump motor, and a lube pump motor that is maybe 1/4hp ,I can't find any reference to the hp of it but it only pushes lube oil to the ways. 

Thoughts?

Thanks


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## benmychree (May 16, 2018)

I have a surface grinder as you describe, it has no trouble running on my 5 HP (homemade ) phase converter.  When you add motors to the circuit, they all act as phase converters, adding, not subtracting from the converter's capacity.  I see no need for an extreme duty unit, since there is no high starting load involved (like maybe an air compressor). Three phase motors in a hobby shop will rarely draw full load amps.  I think the other company that told you that the 3 HP unit is sufficient is telling you the truth.  The machine's nameplate lists full load amps as 7 on 230 volt supply; it is a Brown & Sharpe Micromaster.


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