transformer primary bushing confusion

[Bugman1400]

This appears to be a typical padmount xfmr for a 4160/2400Y system. I'd be really surprised to see a 2400/1386Y system.

 

[Smart $]

... I'd be really surprised to see a 2400/1386Y system.

I believe everyone would. :happyyes:

 

[electrofelon]

All it is saying is the ANSI type 2 is made in those voltage ranges, you still need to look at the nameplate of your particular unit to see it's rating.

But those designations ARE what nameplates usually say, and it really isnt very logical or clear IMO. Someone from mars would not know what voltage to feed the transformer in the second of the following cases: 1) take the grounded Y system case. I just looked at a bunch of them and their namplates. The format is 1.732XGRDY/X and the diagram shows one of the H terminals bonded to the can. So that is easy, we know it is fed line-neutral at a voltage of X. So why do they put the 1.732X figure in there? Just seems pointless and confusing. Anyone installing a transformer probably knows how to calculate the L-L voltage from the L-N voltage or vice versa.

2) Now take a look at this namplate where the designation is X/1.732XY, and tell me what voltage the transformer needs. The way I see it, you either assume from the number of bushings or you have to know what the format means (which I believe means when written like this its a L-L connected transformer thus it needs the higher Y voltage.

 

[electrofelon]

This appears to be a typical padmount xfmr for a 4160/2400Y system. I'd be really surprised to see a 2400/1386Y system.

What about a 2400 delta system, think there is any of those left? I would think that would be a nearly obsolete utility system. In my neck of the woods lots of the single phase rural distribution is two phases of a 4800 delta system - indeed thats what I am served with - but I imagine 2400's were mostly upgraded thats pretty low voltage.

 

[GoldDigger]

2) Now take a look at this namplate where the designation is X/1.732XY, and tell me what voltage the transformer needs. The way I see it, you either assume from the number of bushings or you have to know what the format means (which I believe means when written like this its a L-L connected transformer thus it needs the higher Y voltage.

I do not see that on the nameplate. Is it in the catalog or cut sheet?

The LV designation of 120/240 says center tapped single phase to me, so with four terminals it could be 240 or 120 depending on the coil connections chosen.

The HV designation requires a three phase source to make sense, and if two bushings are insulated, an L-L connection; if one bushing is insulated an L-N connection, choosing the corresponding voltage.

But I would not install and apply power based on that info alone.

 

[electrofelon]

I do not see that on the nameplate. Is it in the catalog or cut sheet?

I provided the general format, note the picture states 7620/13200Y. The two formats described in my last post are used pretty much universally for pad and pole mount single phase transformers.

 

[NewtonLaw]

I am being told this transformer is for a 2400 delta primary system. This doesnt seem correct. It looks to me like it is meant for a wye system and the second bushing is for loop feed...or am I misinterpreting the bushing numbering scheme???

This transformer is connected with the H1 lead attached to a internal bus bar. Two connections are made to this bus and are brought out as H1A and H1B bushing sockets. This connection allows a primary feed through of the attached Phasor conductor. The H2 side of the primary coil is attached to the tank of the transformer. The primary side is designed to be attached in a phase to neutral connection.

If this transformer was designed to be use in delta bank configuration there would be an H1 primary bushing and an H2 primary bushing brought out to allow the transformer to be connected in the delta configuration with two additional transformers. Hope this helps.

 

[electrofelon]

This transformer is connected with the H1 lead attached to a internal bus bar. Two connections are made to this bus and are brought out as H1A and H1B bushing sockets. This connection allows a primary feed through of the attached Phasor conductor. The H2 side of the primary coil is attached to the tank of the transformer. The primary side is designed to be attached in a phase to neutral connection.

correct. I did eventually obtain a photo of the nameplate, I'll attach for completeness.

If this transformer was designed to be use in delta bank configuration there would be an H1 primary bushing and an H2 primary bushing brought out to allow the transformer to be connected in the delta configuration with two additional transformers. Hope this helps.

I would add that such a transformer could be used for a single phase primary line that is two ungrounded conductors from a delta system. Such a system feeds my road: 2 legs of 4800 delta. Lots of single phase delta distribution here in central NY.

 

[electrofelon]

This transformer is connected with the H1 lead attached to a internal bus bar. Two connections are made to this bus and are brought out as H1A and H1B bushing sockets. This connection allows a primary feed through of the attached Phasor conductor. The H2 side of the primary coil is attached to the tank of the transformer. The primary side is designed to be attached in a phase to neutral connection.

If this transformer was designed to be use in delta bank configuration there would be an H1 primary bushing and an H2 primary bushing brought out to allow the transformer to be connected in the delta configuration with two additional transformers. Hope this helps.

What are you thoughts about the primary voltage of the transformer in post #23? I say 13.2....

 

[kwired]

correct. I did eventually obtain a photo of the nameplate, I'll attach for completeness.



I would add that such a transformer could be used for a single phase primary line that is two ungrounded conductors from a delta system. Such a system feeds my road: 2 legs of 4800 delta. Lots of single phase delta distribution here in central NY.

The primary schematic on that one shows H1A and H1B tied together - there is two ports on the same line for feed thru purposes. The other end of the primary just ends at a ground symbol - this unit must be connected to a grounded conductor, 4160/2400 system is the most common system this would work with. My guess is the transformer in post 23 is a similar situation - must be connected to a grounded conductor.

 

[electrofelon]

. My guess is the transformer in post 23 is a similar situation - must be connected to a grounded conductor.

I don't think I agree. One couldn't tell from the picture in post 23, but that is a pole unit with two bushings. Does that change your answer?

 

[Smart $]

I don't think I agree. One couldn't tell from the picture in post 23, but that is a pole unit with two bushings. Does that change your answer?

His reply was to post #28...

As far as my thoughts on post #23, I was satisfied sitting on the sideline for your query... but now that you state it has two bushings, I'll go with 13.2kV.

 

[kwired]

His reply was to post #28...

As far as my thoughts on post #23, I was satisfied sitting on the sideline for your query... but now that you state it has two bushings, I'll go with 13.2kV.

He only asked if it had two bushings if that changed my answer.

All I can say is if it has two bushings and you apply 13.2kV to it and it burns up in short time - it probably was only rated for 7200.:happyyes:

 

[mivey]

But those designations ARE what nameplates usually say, and it really isnt very logical or clear IMO. Someone from mars would not know what voltage to feed the transformer in the second of the following cases: 1) take the grounded Y system case. I just looked at a bunch of them and their namplates. The format is 1.732XGRDY/X and the diagram shows one of the H terminals bonded to the can. So that is easy, we know it is fed line-neutral at a voltage of X. So why do they put the 1.732X figure in there? Just seems pointless and confusing. Anyone installing a transformer probably knows how to calculate the L-L voltage from the L-N voltage or vice versa.

2) Now take a look at this namplate where the designation is X/1.732XY, and tell me what voltage the transformer needs. The way I see it, you either assume from the number of bushings or you have to know what the format means (which I believe means when written like this its a L-L connected transformer thus it needs the higher Y voltage.

The lower voltage is the winding voltage except for dual windings that allow parallel or serial connection (dual voltage transformer).

X is for X volt winding on delta system.

X/1.73XY is X volt winding and can be used on X volt system. It can also be used on a 1.73X system if connected Y.

X/1.73XGrdY is X volt winding and has reduced insulation. Delta connection on X volt system. Y connection on a 1.73X volt system with effectively grounded neutral (because of reduced insulation).

1.73XGrdY/X is X volt winding with reduced insulation on neutral end. Neutral may connect to tank for Y connection or for single-phase connection on a 1.73X system if the neutral end is effectively grounded.

 

[electrofelon]

It's interesting that despite all the knowledgeable people on here, no one seems to be familiar with the designation of that transformer in post 23. That Is not an oddball, just about every single phase mv transformer uses that designation.

 

[mivey]

It's interesting that despite all the knowledgeable people on here, no one seems to be familiar with the designation of that transformer in post 23. That Is not an oddball, just about every single phase mv transformer uses that designation.

Depends on what you have seen. May also be a case of forgetting. The list in my prior post should be a refresher so everyone is back up to speed.

 

[electrofelon]

The lower voltage is the winding voltage except for dual windings that allow parallel or serial connection (dual voltage transformer).

X is for X volt winding on delta system.

X/1.73XY is X volt winding and can be used on X volt system. It can also be used on a 1.73X system if connected Y.

X/1.73XGrdY is X volt winding and has reduced insulation. Delta connection on X volt system. Y connection on a 1.73X volt system with effectively grounded neutral (because of reduced insulation).

1.73XGrdY/X is X volt winding with reduced insulation on neutral end. Neutral may connect to tank for Y connection or for single-phase connection on a 1.73X system if the neutral end is effectively grounded.

So the lower voltage is the primary voltage regardless of the number of bushings? So the post 23 unit is connected l-l on a 7.62 delta system, or l-n on a 13.2 wye system correct?

 

[mivey]

So the lower voltage is the primary voltage regardless of the number of bushings? So the post 23 unit is connected l-l on a 7.62 delta system, or l-n on a 13.2 wye system correct?

Yes and yes.

 

[electrofelon]

Yes and yes.

Good to know thanks for the clarification.

 

[mivey]

Good to know thanks for the clarification.

No problem.