[socalelect]

I'm not to up to speed on exotic transformer connections , so I want to see if something is possible
Customer has 35kva 3 phase genset problem is there are no 3 phase loads , no 3 phase panels etc , generator is having a fit over phase imbalance is there such a transformer with 3 phase y primary with single phase sec ? P
Or another way to go about this ? Reconnection of windings is not possible due to the construction of genset

 

[Big John]

I don't understand why you can't balance the single phase loads among all three phases as is...?

 

[socalelect]

It is because of the way it is tied into the building ,

 

[Ultrafault]

It is because of the way it is tied into the building ,

What does that mean?

 

[Big John]

To answer your question, no, there's no such thing as a 3Ø:1Ø transformer. But I still don't understand why it's possible to install a transformer, but not to split up the feeder?

 

[micromind]

To answer your question, no, there's no such thing as a 3Ø:1Ø transformer. But I still don't understand why it's possible to install a transformer, but not to split up the feeder?

I'd guess that the service to the building is single phase, and the gen is 3 phase.

It's not a good idea to load two legs of a gen and have nothing on the other. Bad news all the way around. And if the gen cannot be re-connected.........

One possibility is a transformer with a 3 wire delta primary and a 4 wire delta secondary. Simply connect the single phase load to the 120 volt legs and the neutral and leave the high leg unconnected.

You'll need to oversize the transformer, and balance the single phase loads as closely as possible.

This set-up won't balance all 3 phases at the gen, but it will spread the load to some degree. Very likely enough that the gen won't act up much.

 

[socalelect]

What does that mean?

Customer has single phase SVC with manual transfer switch , uses generator during the day to cut power bill apparently he gets nasty diesel fuel cheap and his gen likes it

 

[socalelect]

I'd guess that the service to the building is single phase, and the gen is 3 phase.

It's not a good idea to load two legs of a gen and have nothing on the other. Bad news all the way around. And if the gen cannot be re-connected.........

One possibility is a transformer with a 3 wire delta primary and a 4 wire delta secondary. Simply connect the single phase load to the 120 volt legs and the neutral and leave the high leg unconnected.

You'll need to oversize the transformer, and balance the single phase loads as closely as possible.

This set-up won't balance all 3 phases at the gen, but it will spread the load to some degree. Very likely enough that the gen won't act up much.

How much over size are ya thinkin ?

 

[micromind]

How much over size are ya thinkin ?

Somewhere around twice the expected load.

The trouble here is there are 3 coils in this transformer, and only one of them is being used for 120/240 single phase loads.

The other two will share part of the load, but not a lot.

 

[socalelect]

Somewhere around twice the expected load.

The trouble here is there are 3 coils in this transformer, and only one of them is being used for 120/240 single phase loads.

The other two will share part of the load, but not a lot.

Wouldn't 2 of the coils be used ?

 

[Birken Vogt]

I fix generators. It is possible to get three phase through transformers but it seems an expensive way to go. I am not quite ready to take your word that it is not reconnectable. What kind of a generator is it? Do you have a diagram of the alternator connection points? Or is this one of the old railroad 2-71 GMCs? What kind of a fit is it having, exactly? Sometimes these things can be worked around by picking the 2 legs that are regulated and leaving one unregulated leg run wild and unloaded. It sounds like the customer is not having problems with the equipment running on 208v, correct?

 

[socalelect]

I fix generators. It is possible to get three phase through transformers but it seems an expensive way to go. I am not quite ready to take your word that it is not reconnectable. What kind of a generator is it? Do you have a diagram of the alternator connection points? Or is this one of the old railroad 2-71 GMCs? What kind of a fit is it having, exactly? Sometimes these things can be worked around by picking the 2 legs that are regulated and leaving one unregulated leg run wild and unloaded. It sounds like the customer is not having problems with the equipment running on 208v, correct?

Birken , all the way over here from wlf ?
Good call on it being a old RR gen , its a 3 71 not a 271. Its voltage output is 225. On the nameplate

 

[socalelect]

 

[dmxtothemax]

is there such a transformer with 3 phase y primary with single phase sec ?

NO !


If your tring to run a single phase load, off a three phase genny,
then the only way is to reconfigure the main panel bus arrangements.
of the building.
Have you looked at the main panel ?
Is it a split bus ?

Not a small or cheap job, but possible,

You would be better of swaping the genny with someone who has
a single phase genny surplus !

Or maybe offer free power to the neighbours,
and put them on the other two phases !
Instant friends !


The right genny ! for the right job !

 

[socalelect]

There's the nameplate ,

 

[Birken Vogt]

Yes, I was a FF in the past and might be again this season.

Being a RR gen there are only 3 hots and no neutral, correct? No midpoint taps in the stator, correct?

I am still unclear on what the root problem is to the customer's facility.

 

[socalelect]

NO !

If your tring to run a single phase load, off a three phase genny,
then the only way is to reconfigure the main panel bus arrangements.
of the building

Not a small or cheap job, but possible,

You would be better of swaping the genny with someone who has
a single phase genny surplus !

Or maybe offer free power to the neighbours,
and put them on the other two phases !
Instant friends !

The right genny ! for the right job !

Yea he won't go for reconfiguring tried that

 

[socalelect]

Yes, I was a FF in the past and might be again this season.

Being a RR gen there are only 3 hots and no neutral, correct? No midpoint taps in the stator, correct?

I am still unclear on what the root problem is to the customer's facility.

Its got a noodle , the issue is the voltage goes output of the gen becomes unstable when only 2 legs are loaded , I have load banked this unit on 3 phase and it did very well and had stable voltage and freq

 

[socalelect]

I'm not sure about any taps in the windings , its all concealed within the housing , only has 4 wires coming out of the housing. , its nothing like the mqs I'm used to working on

 

[dmxtothemax]

Yea he won't go for reconfiguring tried that

Can you find some load for the other two phases ?
Is it an industrial facility or domestic ?
Perhaps put up some big power sucking outdoor floodlights ?
And hang them on the other two phases ?

View attachment 33789

Put up as many as you need,
may be six lights total,
Three each on the two other phases.