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# Operating Voltage of Mains transformer

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#### Urahara

##### Member
Hello

For a 2VA or less step-down transformer from primary mains voltage to say 12V secondary, if the transformer datasheet specifies a mains voltage of 230V, does it mean then that it can operate btw 200-250V AC? If it specifies 115V, does it mean it can operate btw 100-125V AC?

Thks!

Hello

For a 2VA or less step-down transformer from primary mains voltage to say 12V secondary, if the transformer datasheet specifies a mains voltage of 230V, does it mean then that it can operate btw 200-250V AC? If it specifies 115V, does it mean it can operate btw 100-125V AC?

Thks!

hi,
You can use a 230V rated transformer on 200V thru 250V, but the output voltage will change as the transformer ratio.
So 230/12 = 19.17, say 19:1

So 200V/19 =10.5V and so on..
250/19 = 13.15V

Likewise for the 115V transformer.

The other point is the VA rating.
Say the 12V at 2A = 24VA, then for the highest voltage of 250V the output current [ to stay within spec] would be 24VA/13.15 = 1.8A

Hi Eric

Many thks to your prompt responses to this query and previous ones too!

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