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sizing a control transformer
- Thread starter tomjelly
- Start date
- Replies 7
- Views 1,226
TDegenhart
Diamond
- Joined
- Mar 26, 2011
- Location
- Geneva Illinois USA
Is this a long control line as in 20-30 feet from the contactor? If so then the resistance and capacitance of the wires have to be taken into account. A good introduction to calculate the size transformer is in this reference.
http://dl.icdst.org/pdfs/files3/10b9a68e57a32575e7d5aa774ff2f1d8.pdf
Just from experience I would say 75VA minimum.
Tom
http://dl.icdst.org/pdfs/files3/10b9a68e57a32575e7d5aa774ff2f1d8.pdf
Just from experience I would say 75VA minimum.
Tom
SomeoneSomewhere
Hot Rolled
- Joined
- Dec 24, 2019
If it's all in the same cabinet, just use a 240V contactor. Your switch should be rated for it.
atomarc
Diamond
- Joined
- Mar 16, 2009
- Location
- Eureka, CA
240 volts at the button is considered lethal voltage and is verboten in many places...as I recall.
Stuart
Stuart
SomeoneSomewhere
Hot Rolled
- Joined
- Dec 24, 2019
Might be a regional thing. A lot of simple control equipment here in NZ has 400V on the buttons.
As long as the button is suitably rated for mains voltage and all wiring is contained in the box, there's nothing wrong with it - 277V light switches exist, too.
As long as the button is suitably rated for mains voltage and all wiring is contained in the box, there's nothing wrong with it - 277V light switches exist, too.
EmGo
Diamond
- Joined
- Apr 14, 2018
US is a little more safety-conscious. They don't run 220v to the vacuum cleaner, either
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