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Old 02-09-2019, 12:46 PM   #1
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Default Need help with sizing an autotransformer

I don't do this much. I looked online but get conflicting help. Here's my specs.

The load is 240 VAC, 29 amps. I have a shy 208 available volts. This is single phase.
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Old 02-11-2019, 07:42 AM   #2
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Is there nobody home?
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Old 02-11-2019, 07:45 AM   #3
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You size it by the difference in voltage times the amps. So,

240-208 = 32

32 x 29 = 928

1 kVA transformer.
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Old 02-12-2019, 09:07 AM   #4
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Is the secondary voltage determined by the voltage increase that I need?
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Old 02-12-2019, 09:13 AM   #5
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Quote:
Originally Posted by John M. View Post
Is the secondary voltage determined by the voltage increase that I need?
Yes, you want a 16/32 volt secondary.
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Old 02-12-2019, 12:22 PM   #6
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Also when you do the connection for autotransformer or Buck and Boost set up please make sure you follow the wiring connection diagram if they come with it due there is many way to do that so make sure you get the manufacter wiring connection diagram to make sure you are right on the spot.

and yuh you only need one BB that it. ( on single phase but three phase you need two or three depending on the set up )

the last thing you have to be aware is line to neutral voltage will be different after the BB set up. so if you have line to neutral loads be aware of it.
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Old 02-12-2019, 06:16 PM   #7
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Quote:
Originally Posted by frenchelectrican View Post
Also when you do the connection for autotransformer or Buck and Boost set up please make sure you follow the wiring connection diagram if they come with it due there is many way to do that so make sure you get the manufacter wiring connection diagram to make sure you are right on the spot.

and yuh you only need one BB that it. ( on single phase but three phase you need two or three depending on the set up )

the last thing you have to be aware is line to neutral voltage ON THREE PHASE will be different after the BB set up. so if you have line to neutral loads be aware of it.
Fixed it for you
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Old 02-12-2019, 07:15 PM   #8
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Fixed it for you
yuh but I am aware it do affect the line - neutral connection only after the buck/Boost transformer on both single and three phase verison.
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