How To Electrical - star vs delta with 3ph 380V and vfd

Nathan the Machinist said:
View attachment 2004899

This blue wire here on the bridge. It is my understanding that, by European convention, that is neutral. Is this correct? It's weird to see that there but if that is in fact how this motor works, you need to feed it WYE, not delta 3ph.
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Standard industrial connections are rendered mute when connecting thru a VFD. VFD creates a separate circuit.
 
Nathan the Machinist said:
View attachment 2004899

This blue wire here on the bridge. It is my understanding that, by European convention, that is neutral. Is this correct? It's weird to see that there but if that is in fact how this motor works, you need to feed it WYE, not delta 3ph.
Click to expand...

I believe you are correct in that is a neutral. If this was a single speed running off of high voltage that would be the neutral.

If what I understand is happening he is changing it to VFD with three phase output, so he would remove that wire on the jumpers.

Is that what you are thinking as well?

To your earlier post. Delta high leg, 120 degrees apart. Hate delta high leg! Lol A73C6546-A2DF-4548-807C-04C1686CC201.jpeg
 
DaKruiser said:
I believe you are correct in that is a neutral. If this was a single speed running off of high voltage that would be the neutral.

If what I understand is happening he is changing it to VFD with three phase output, so he would remove that wire on the jumpers.

Is that what you are thinking as well?

To your earlier post. Delta high leg, 120 degrees apart. Hate delta high leg! Lol View attachment 2004903
Click to expand...

Yes, that is Delta high leg. Which is what is output from most phase converters and variable frequency drives. (Edit: I'm having a brain fart here, that is incorrect) But, around here, most variable frequency drives are sending through the two hot legs so they are 180° apart which is what necessitates the high leg. That's why I asked what he was feeding his variable frequency drive, because if it is one leg of neutral and one leg of 220, it isn't sending that through that way. So it might actually be sending out true WYE 120° apart.


Edit: hold up I'm not thinking about this right. Variable frequency drives do not send through the two legs. I'm thinking of rotary phase converter and a static phase converter. A variable frequency drive does not send through the legs.
 
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That would probably be a much more complicated VFD to do that because it's basically acting like an amplifier. It would need a big filter capacitor and it would be running a high-powered DC bus to do that. That's complicated and not normally the way it's done, but perhaps that's how his works.


Edit. I am mistaken here. That is how a variable frequency drive works. That's not how a phase converter or static phase converter works but, that would in fact be the way that it works. I'm wrong.
 
I got confused here because he's using a variable frequency drive as a phase converter for this machine. But yeah, a VFD should send out three equal legs. I'm still not sure why there's a neutral on that bridge and what happens if you remove it.
 
But, if it is supposed to be there, there's nothing stopping you from taking the utility neutral and putting it there. Assuming you are getting equal legs out of that VFD, which you probably are. Personally I would verify that, because if it is, for whatever reason, (high leg) Delta 3 phase like you would get out of a regular phase converter you risk damaging your motor.
 
I am also in Europe. I run my 3-phase motor discgrinders and buffer from a VFD that has 230V input:

Delta:

fEwRrAJ.jpeg


My grinders I run on 380V input through another VFD, that has 380 V in and 380V out: Star.
 
Scaniaman said:
I am also in Europe. I run my 3-phase motor discgrinders and buffer from a VFD that has 230V input:

Delta:

fEwRrAJ.jpeg


My grinders I run on 380V input through another VFD, that has 380 V in and 380V out: Star.
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Does the 380 volt star set up use a neutral or is it just the three live wires?
 
Scaniaman said:
Just the three phases, no neutral.
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Here is what he has right now. And that wire on the bridge looks like it is a blue wire if you look higher up on the insulation. And if I'm not mistaken I think that a blue wire in France means neutral. I'm trying to wrap my head around why that is there and what happens if you hook up a neutral to that spot. It's weird.
 
Nathan the Machinist said:
View attachment 2005206

Here is what he has right now. And that wire on the bridge looks like it is a blue wire if you look higher up on the insulation. And if I'm not mistaken I think that a blue wire in France means neutral. I'm trying to wrap my head around why that is there and what happens if you hook up a neutral to that spot. It's weird.
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You're right. I haven't seen that before, and I have no clue. Without knowing any better I'd just ditch that wire and hook it up delta.
 
Problem with 3ph is in the grid. It's impossible to level the power thru all 3ph. Delta is troublesome here. In a star connection the neutral is for protection of the motor as it levels the power when it's out of balance. Essentially undervoltage is corrected out. Second protection is grounding. Phases push the motor, neutral is for protection only. VFD creates a separate circuit that doesn't have grid issues. So there is no need for neutral.
 
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Nathan the Machinist said:
View attachment 2005206

Here is what he has right now. And that wire on the bridge looks like it is a blue wire if you look higher up on the insulation. And if I'm not mistaken I think that a blue wire in France means neutral. I'm trying to wrap my head around why that is there and what happens if you hook up a neutral to that spot. It's weird.
Click to expand...

H HSC /// what does the other end of this blue neutral connect to? A starting device?
 
I was looking around online and what I found said that there is really no current on that point and you can hook neutral to it to pull out some of the harmonics and that most people don't, but you could.

I did not know any of that.

But now I do.

Except I don't.

But, from what I read, you can omit it and it won't hurt anything, or you can put a neutral on that bridge and it might in theory be a good thing. It shouldn't hurt? I would do it.

I also would use a neutral from the utility and not just the ground. Because I don't like getting randomly shocked.
 
What is interesting to me is that the neutral at that point is not really intended to carry a current. It could carry a current if there was some wonky imbalance or whatever, and strictly speaking it is not necessary, but you can put a neutral at that point. That's pretty cool. I learned something today.
 
I have learned that a fourth lead can be added to a 3 phase system hooked up in Y/star. I would guess maybe in this case that lead's other end has been connected to a 230 V start/ break device..?

And to sum up: get a 4 lead wire (3 phases and ground) and forget all about that neutral when hooking it up through your VFD
 
I think ya'll might be missing the point the motor was originally wired to something other than VFD when the blue wire was used. Now, per the diagram in post #3 shows the motor is wired for a Wye (Star) connection with the blue wire connected. No idea how it was used originally.. For wiring to VFD the only wires needed are the 3 phases connecting to R, S, T and a ground wire connected to frame of motor.

Listen to JoeBusic, he seems very knowledgeable of wiring methods over there. Their methods are different than on this side (USA) of pond. Over here we tend to purchase VFD that take 1 ph 220 vac that uses 2 hot wires and a neutral. Over there they tend to use 1ph 220 vac that uses one hot wire and neutral. Of course ground wire for safety. The VFD is still going to put out 3 phases (wires) of voltage depending on voltage needed.

USA 3 ph motors tend to be dual voltage (230/460) that is wired in Wye (Star) mode. A motor has 6 coils giving 12 leads. Normally the T10, T11, & T12 leads are tied together inside the motor bringing 9 leads out putting the motor in the Wye wiring. I've seen a few 12 lead motors with no labels on the leads. That always requires sorting the polarity of the coils to wire up.

As Nathan said, lots of good knowledge in this thread, but also some errors so read with caution.
 
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