Buck Boost Transformer

[GoldDigger]

It's working now, and using 13.3%, I got the exact same answer.

Where did I go wrong in my formula? I'm off by a factor of 10.

I thought it was based on the boost voltage and load current.

The web site is a bit confusing. The recommended transformer is 2S46F, which, if you look it up in the catalog, is a 2KVA transformer.
The wattage figure shown, 19.47 KVA, is the total output power (apparent) of the boost circuit, all of which is ultimately derived from the input, but only a fraction of that power has to pass through the boost transformer itself.

 

[growler]

I would say the 60a number. Remember, you only need to size the transformer for 60 x (240-208) = 60 x 32 = 1920 = 2 kVa.

The equipment is a Hot Tub. It has two, maybe three motors, and heaters.

It's working now, and using 13.3%, I got the exact same answer.

Where did I go wrong in my formula? I'm off by a factor of 10.

I thought it was based on the boost voltage and load current.

Larry they have a separate calculator for motor loads. If you run the numbers there you get the 1920 VA or 2 KVA.

But Bill says the load will be motors and heaters so I don't know if you can use that calculator using only the boost voltage.

I think I would talk to someone at Eaton or Square D about the sizes.

 

[berad]

Buck Boost Transformer

Great Information

 

[LarryFine]

The web site is a bit confusing. The recommended transformer is 2S46F, which, if you look it up in the catalog, is a 2KVA transformer.

Thank you. I was taken aback when I suddenly thought I had it wrong all these years. :blink:

 

[LarryFine]

Larry they have a separate calculator for motor loads. If you run the numbers there you get the 1920 VA or 2 KVA.

But Bill says the load will be motors and heaters so I don't know if you can use that calculator using only the boost voltage.

With the 125% allowance, why would the heaters change the calculation?

 

[brantmacga]

I buy mine from Hammond; I typically use the square D Calc to size it, but the people at Hammond can also tell you what you need.

I’ve had to use quite a few on pool pump installs at houses with 208Y/120 services.

Sent from my iPhone using Tapatalk

 

[Little Bill]

I got the transformer and hooked it up. The actual voltage that I measured was 213V so I got a little over 240V with the transformer.

 

[LarryFine]

I got the transformer and hooked it up. The actual voltage that I measured was 213V so I got a little over 240V with the transformer.

With no load, that's perfect.