Buck down transformer sizing question

I am purchasing a buck down transformer to go from 245V to 216v and I wanted to feel out proper sizing based on my machind amperage draw.

My machind pulls 9.6Kva full load. I can go with a 10Kva unit or a 15Kva unit. I don't mind the price difference.

Is there any benefit to upsizing the buck down tranformer beyond better to have it and not need it?

Thanks in advance.

A buck or boost transformer carries the power DIFFERENCE proportional to voltage and ohms law.

Check any on-line calculator for your own better understanding.

Go here> Buck and Boost Transformer Calculator - Schneider Electric United States.

Very easy to use. When you get the specs of the recommended transformer, you will see that size is a lot smaller than full load.

Tom

countryboy1966 said:

Is there any benefit to upsizing the buck down tranformer beyond better to have it and not need it?

Click to expand...

The terminology is "buck" for a lower voltage, "boost" for a higher voltage. You don't need to write it as "buck down".

If you don't mind the price/size difference it's always better to over-build a system.

All you really need to know is the load current. Any buck (or boost connected) transformer with a low voltage side rated somewhat over that load current will work. That automatically deals with the VA rating.

countryboy1966 said:

I am purchasing a buck down transformer to go from 245V to 216v and I wanted to feel out proper sizing based on my machind amperage draw.

My machind pulls 9.6Kva full load. I can go with a 10Kva unit or a 15Kva unit. I don't mind the price difference.

Is there any benefit to upsizing the buck down tranformer beyond better to have it and not need it?

Thanks in advance.

Click to expand...

Reading between the lines a bit...Buck transformers normally don't come in even KVA values as you listed. It's a calculated number based on the application. Additionally you didn't mention 1 or 3Φ application. If your load is 3Φ then you would require two 1Φ transformers to get an open delta output. Does your machine load care if it's a supplied open delta source?

General rule on sizing is run the numbers and pick the combination that meets the load current, or use the next standard size up. Going larger won't hurt, may be beneficial for larger future loads, but cost more to obtain and wire, and has more standby losses.

Running some numbers, based on 9.6KVA 245V buck to 216V ~ 29V reduction, 13.3% Change. Closest match in standard units 32V secondary buck. Type 120x240V-16/32V 245V-32V = 213V output

3Φ Calculated Rating 13.26KVA 245V to 216V using, Two 1KVA units 120x240-16/32V In a Delta to Open Delta Configuration


1Φ Calculated Rating 11.47KVA 245V to 216V using, One 1.5KVA unit 120x240-16/32V In a Single Phase Configuration.


You could go larger on both counts, but either of the above choices should be suitable.

SAF Ω

Thanks for the assistance everyone including helping me get my terminology straight.

Moving forward! Thanks