Single Phase Transformer

[charlie b]

I am reviewing a design for a small facility that has a large 480 volt motor but very little 120 volt load. The design shows a 25 KVA, 3-phase step-down transformer. I was asked whether the load could just as easily be served by a single phase 480-120V transformer, perhaps no larger than 15 KVA. Two questions:

1. Does such an animal exist?
2. Is it rare enough (i.e., low demand, not a standard off-the-shelf item) that it would be cheaper to buy a 15 KVA 3-phase transformer and only connect one phase?

I would prefer not to offer a "cost savings idea" that would not actually save costs.

 

[petersonra]

I am reviewing a design for a small facility that has a large 480 volt motor but very little 120 volt load. The design shows a 25 KVA, 3-phase step-down transformer. I was asked whether the load could just as easily be served by a single phase 480-120V transformer, perhaps no larger than 15 KVA. Two questions:

1. Does such an animal exist?
2. Is it rare enough (i.e., low demand, not a standard off-the-shelf item) that it would be cheaper to buy a 15 KVA 3-phase transformer and only connect one phase?

I would prefer not to offer a "cost savings idea" that would not actually save costs.

I use single phase 480/120V control transformers in that range now and then. This is the one I usually use for 15 KVA applications.

ACME T2535173S Transformer, 15KVA 240X480Pri/120X240Sec, TYPE 3R ENCLOSURE, ENCAPSULATED

I don't recall the exact price but it was something like $500 or $600.

 

[kwired]

I am reviewing a design for a small facility that has a large 480 volt motor but very little 120 volt load. The design shows a 25 KVA, 3-phase step-down transformer. I was asked whether the load could just as easily be served by a single phase 480-120V transformer, perhaps no larger than 15 KVA. Two questions:

1. Does such an animal exist?
2. Is it rare enough (i.e., low demand, not a standard off-the-shelf item) that it would be cheaper to buy a 15 KVA 3-phase transformer and only connect one phase?

I would prefer not to offer a "cost savings idea" that would not actually save costs.

25 kVA is a common size for single phase transformer, but for three phase they usually go from 15 to 30 kVA.

 

[ActionDave]

Two questions, Does such an animal exist?

Yes. Little bit different size like kwired mentioned and it will likely be a 120/240 secondary.

Is it rare enough (i.e., low demand, not a standard off-the-shelf item) that it would be cheaper to buy a 15 KVA 3-phase transformer and only connect one phase?
I would prefer not to offer a "cost savings idea" that would not actually save costs.

It's not so rare to not consider it, but I know what happens every time is that a month goes by and somebody wants to hook something up that is three phase, and then you buy two transformers.