Homebrewed Electricity > Controls

HELP with 220v step up transformer wiring

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Kevinkay:
YES!
Thank you mab and magnetjuic!
I have to say I doubted this and took extra precautions connecting a wire giving me 120v line to the side that has a wire going back to the neutral of the incoming voltage, but it worked!

I now get 245v across the 220 outlet terminals.  "N" to ground gives 245v, "L" to ground results in 0v
the 120 outlet give me 120V across terminals. "N" to ground gives 120v, "L" to ground results in 245v

when I switch the input switch to 220v (even though its only getting 120v) it "halves" the output at the outlets, 60v at the 120 outlet and 120 across the 220 outlet.

There is a "buzz/hum" now while the unit is plugged in and running, switching the breaker off, kills the output voltage and the buzz.
I am thinking this buzz is normal and getting 245v (on a 220v-240v outlet) is with in normal range?
And I am mistaken on L meaning load and N meaning neutral???

Thanks for all the responses, I posting the working wiring diagram

"If you wanna go fast - go alone, if you wanna go far, go together"

MagnetJuice:
Hi Kevin,

Good to hear that you got it working.

245V is a bit high, but it will come down when a heavy load is connected.

As for the hum, all transformers do that, except for the very old ones. For some reason the old transformers were built tighter and a lot of them had the coil potted in some epoxy or polyester, then enclosed in a metal case. I have some of those and they run very quiet.

Noise drives me crazy. On some of my big power supplies, I remove the transformer and mount it back using rubber grommets to isolate it from the metal case. That usually kills the humming. Most of the time, the hum can be reduced by adding soft rubber feet to the case.

Ed

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