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Low voltage application- wye or delta

Don Gitzel

Aluminum
Joined
Jul 25, 2017
I sold a guy a phase converter. He is asking me if my converter is wye or delta because he has a choice of wiring his lathe in wye or delta on low voltage. The idler winding are wye however I read on the forum it is an considered an open delta source. ??
I can’t seem to post a picture of the wiring diagram. What is the advantages of either wiring configuration. Just wondering how to respond to him. Thanks guys.
 
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He needs to connect his lathe for whatever the output voltage of the converter is.

That's going to depend on how his motor is wound.
 
I sold a guy a phase converter. He is asking me if my converter is wye or delta because he has a choice of wiring his lathe in wye or delta on low voltage. The idler winding are wye however I read on the forum it is an considered an open delta source. ??
I can’t seem to post a picture of the wiring diagram. What is the advantages of either wiring configuration. Just wondering how to respond to him. Thanks guys.

An idler or load-motor cannot be connected true "Wye" unless it has a five-wire - (each of 3-Phases, Neutral, plus PE), feed. At which point it would not be an RPC idler. Proper 3-Phase, rather, and just one more ignorant motor using that!

:)

In general... RPC are inherently Delta-out. So are Phase-Perfect. And VFD, if it matters.

Phase-Perfect publish the schematic and specifications for use of a Delta-Wye transformer when Wye is needed. Or simply preferred. Not that it is in any way complicated!

I use one - an EGS-Hevi-duty 27 KVA "Drive Isolation" transformer, Delta-in, Wye-out.

But my loads motors are optioned and connected Delta - the re-derived or "local" Neutral not even carried the "last inch".

I just don't like corner-grounded Delta, is all!

:D
 
iCloud

Here’s his question.

“” Yes I realize that the output is 240v. My guestion was is the converter output wye or delta because as you can see according to the drawing the wiring is different for both””
 
iCloud

Here’s his question.

“” Yes I realize that the output is 240v. My guestion was is the converter output wye or delta because as you can see according to the drawing the wiring is different for both””
 
It doesn't matter and/or isn't a question that can be asked. Equipment can be connected star or delta. Lines are just that.

Assuming the third image is of his motor, he needs to read his nameplate, which will tell him what voltage to supply for each combination of low/high voltage and star/delta. Only one will match 230V 60Hz.
 
Thanks for the reply. I understand the concept of wye/delta starting to mitigate the high voltage spike, but why switch to delta. All the smaller motors I have seen are wired Wye. You guys rule!!
 
Delta Wound 12 Lead RPC Idler Motor

It appears that the motor your using is made as a 12 lead delta wound machine.

For the low voltage connection the diagram you posted on iCloud, shows both wye and delta, more specifically double wye or delta. The wye connection is used for starting only and applies half voltage to each winding, to keep the starting current spike lower. But that is for momentary use only.

The delta connection is used for the run mode and provides full voltage to all of the windings. The motor can be started and run on the delta connection, without a wye/delta 9 pole motor starter.

Attached are a couple of drawings in the American style for reference. Similar to your IEC style, but labeled differently and a bit easier to comprehend the winding layout and interconnections.

12LeadDeltaWoundDualVoltage.jpg

12LeadDeltaWoundDualVoltageUS.jpg

12LeadDelta-iCloud Photos.jpg

A delta wound motor is not the best choice for a RPC idler, because when you apply single phase, you are only energizing one pair of windings in the delta. The other two are unpowered.

With a more typical North American 9 lead wye wound motor, when you apply single phase, you are energizing two of the three sets of windings, and getting twice the input, to magnetize the motor.

I think you proved this out to yourself, by saying your delta wound RPC would not start an equal sized wye wound unloaded motor. For best results switch the motors around and re-balance the RPC and try your test again.

SAF Ω
 
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Ok. How do I tell if a motor is y or delta. If it is nine lead and 4,5&6 are connected then I can assume it is y. ???
 
….

A delta wound motor is not the best choice for a RPC idler, because when you apply single phase, you are only energizing one pair of windings in the delta. The other two are unpowered.

...
SAF Ω

Ummmm…. In my mind, all 3 windings in delta receive current. Not sure what you mean.
And I have found 230v 12 wire delta motors make the best RPCs.
They run the most quiet with no buzzing.
Just wondering what you mean.

-Doozer
 
a wye will have a diagram like a Y shape.
Delta is a delta triangle shape for the wiring diagram.

and no, not always if they are connected together, those leads just set the input voltage. making it a low 230V or high 600V connection.
 
iCloud

Here’s his question.

“” Yes I realize that the output is 240v. My guestion was is the converter output wye or delta because as you can see according to the drawing the wiring is different for both””

The other guy is mistaken about the entire concept.

Whether a MOTOR is internally connected wye or delta is a decision made by the motor mfr, having to do with coil wire sizing, slot sizing inside the stator, etc. etc. That has NOTHING TO DO WITH the incoming power being wye or delta. Nothing. From the motor's standpoint, there is just 3 phase coming in. That's it.

SOME motors, typically made for countries adhering to British Standards (BS), use wye or delta connections to change the VOLTAGE that the motor can be connected to. So for example 220/380V, 230/400V or 240/415V (depending on the age) because the two different voltages are related to the square root of three to each other (400/1.732 = 230, etc. etc.). So if you have 230V available, you connect the motor with its windings configured in the delta pattern, if you have 400V available, you connect to the motor with its winding in a wye (star) pattern. We (North America) do dual voltage motors differently, and it has no relation to being wye or delta. You can get dual voltage wye wound motors, or dual voltage delta wound motors. Totally different concept here.

So if he says that he has a motor that can be connected either way, it MUST be one of those BS motors, and it can ONLY be connected for 230V in its delta pattern, otherwise if he connected his motor in delta and fed it 230V, it will not produce much torque and likely stall out.

But again, this has NO BEARING WHATSOEVER on what the configuration of the RPC (or generator, or utility transformer) looks like, all you are doing is giving the motor 3 phases.
 
I sold a guy a phase converter. He is asking me if my converter is wye or delta because he has a choice of wiring his lathe in wye or delta on low voltage. The idler winding are wye however I read on the forum it is an considered an open delta source. ??
I can’t seem to post a picture of the wiring diagram. What is the advantages of either wiring configuration. Just wondering how to respond to him. Thanks guys.


Every three phase standard motor I have ever seen takes in power on three wires. There may be anything inside the motor, but that does not matter.

Three wires is all it takes to supply 3 phase power. And 3 wires is possible with EITHER a "delta" source, OR a "wye" source.

Motors can be wired internally with the various coils connected in wye or in delta. However, those correspond to two DIFFERENT voltages. A 230V motor connected internally as "delta", will have three coils each taking the line-to-line voltage of 230V. (It will have three input wires for the power.) If reconnected as "wye", it will be ready for use at 400V line-to-line.

NO regular 3 phase motor I am aware of uses the neutral for any purpose at all. If the motor is connected internally as "wye", there will be a "neutral point" internal to the motor, but that point is never connected externally to the power source. Only three wires are used for power regardless of the internal connections. Consequently, the internal wiring of the motor is ONLY important as it applies to getting the wiring correct for the voltage it needs to work on. The type of source, so long as it is three phase of the correct voltage, does not affect the motor, which only uses 3 wires, Whether the source is wye, delta, corner grounded, wild leg 3 phase, or whatever.

If the source happens to be a rotary phase converter, the output of it will be "wild leg 3 phase", also known as "high leg 3 phase", "farm 3 phase", "lighting tap 3 phase", "stinger 3 phase" and other names.

But that is not relevant to the internal wiring of the motor, so long as the motor is set up for the voltage that is being supplied.
 
Star-delta start requires six wires. Likewise with pole-changing motors. I believe the US double-delta and double-star motors have similar options for reduced-voltage starting.

Of course, you then need more than three poles of switch/contactor.
 








 
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