Did I purchase the wrong transformer?

[racer_41]

Hello.
I needed to purchase a transformer to convert 480VAC 3 phase to 240 VAC single phase. I used the configurator to spec it out but when it arrived the 240 output is delta. Can I use two of the legs to get my single phase?
This is the one: Square D 9T75F https://www.grainger.com/Grainger/SQUARE-D-General-Purpose-5B618

Thanks!

 

[augie47]

Their written definition leaves a lot to be desired,but if the pictured transformer is correct the diagram shows a 480 or 240 single phase input with a 240 or 240/120 single phase output so if you want 480 input and 240 output you are all set.

 

[petersonra]

It appears to be fine. very pricey though. maybe square D transformers cost 2-3X what other brands do though.

 

[racer_41]

Thanks for the replies! I did get a substantial discount over the list.

 

[winnie]

I believe that the picture on the grainger page does not match the transformer being described.

The _picture_ on the grainger page shows a single phase 0.05 KVA transformer. The description is of a 3 phase 9 KVA transformer.

Searching for the model number given in the description (9T75F) pulls up a nameplate showing an _open delta_ transformer with no center tap for grounding.

Depending on how the core is arranged, it _might_ be possible to use it as a 4.5 KVA 480 to 120/240 single phase transformer, but it is clearly intended to be a three phase to three phase step down transformer.

 

[petersonra]

you can still get 240V single phase out of it. Just connect to any two of the leads on the secondary and feed 480V to the corresponding two leads on the primary. you will only be able to get 3000 VA though.

 

[steve66]

It appears to be fine. very pricey though. maybe square D transformers cost 2-3X what other brands do though.

I think some suppliers are a "gotta have it fast - willing to pay whatever it costs" type place. Or maybe its like the Square D catalog - nobody pays list price??

I believe that the picture on the grainger page does not match the transformer being described.

The _picture_ on the grainger page shows a single phase 0.05 KVA transformer. The description is of a 3 phase 9 KVA transformer.

Searching for the model number given in the description (9T75F) pulls up a nameplate showing an _open delta_ transformer with no center tap for grounding.

Depending on how the core is arranged, it _might_ be possible to use it as a 4.5 KVA 480 to 120/240 single phase transformer, but it is clearly intended to be a three phase to three phase step down transformer.

No the picture doesn't match the description at all. I think you got a 3 phase transformer. You can still use it for single phase, but you will have extra leads that need to be insulated, and you won't get the full 9VA capacity.

 

[jim dungar]

The T in the Square D catalog number means Three-Phase, it would be an S if it was single phase.

A 9kVA three-phase is effectively (3) 3kVA single-phase units.

So, you can use only two legs (one winding) as long as you only need 3kVA.

 

[Jraef]

I think the root problem here lies in your description:

I needed to purchase a transformer to convert 480VAC 3 phase to 240 VAC single phase.

You don't "convert" 3 phase to single phase, you USE 3 phase OR single phase. So when you went to look for a transformer that accepted 480V 3 phase, it will give you a 3 phase transformer; 3 phases in, 3 phases out, which is EXACTLY what you got.

All you needed to do, since what you WANTED was 240V single phase, was to buy a 480 to 240V single phase transformer.

 

[augie47]

I foolishly looked at the diagram of the transformer pictured unlike the wiser gentlemen in the above posts.
As noted, you might be able to use the transformer supplied depending on the VA required, but also as noted there would be a more suitable transformer.

 

[kingpb]

This is such a perfect example as to why for years I have stressed the importance that you need to understand the differences in voltage designations.

Looking at the data clearly indicates this is a 480V 3ph - 240V 3ph transformer. I would also say you do not have a connection for 120V. This is a 240V 3ph delta.

120/240V is NOT 240/120V.

From ANSI C84.1:

 

[kwired]

Those that thought price was a little high - it maybe was because it is a three phase unit and not a single phase unit.


More support for it being three phase model?

"standard" sizes of three phase transformers typically include a 9kVA unit

"standard" sizes of single phase transformers typically do not include a 9kVA unit they go from 7.5 to 10.

 

[USC2DWR]

Wrong transformer and wrong terminology

Wrong transformer and wrong terminology

Hello,
You need to order a single phase transformer.From the 3 phase 480v supply you need to bring in single phase 480v.This is done by bringing 2 wires from 2 hot 480 incoming.(Note: this will be a single phase as there is 480v between main 480wire 1 & 2, one single phase between wire 2 & 3 and one single phase between wire 1 & 3).Phase is the voltage between any two wires (does not matter if both are hot or if one of them is neutrally grounded.)

As I said the two hot wires incoming will connect to primary side of a single phase transformer and the output will be single phase 240.the primary side current rating max will be 9000VA/480v. So size the ckt bkr accordingly.



Transformer never does phase conversions.They just increase or decrease the voltage whether its a single phase or three phase.Its a dumb terminal and cannot differentiate between different phases.

 

[weressl]

Thanks for the replies! I did get a substantial discount over the list.

The 'list' price isn't really what they expect to get. The pricing structure is established way above the cost plus expected profit they intend to collect, but it is established to be used with multipliers for several years with various users, so they do not have to reprint their catalogs every year.