Circuit - VARIABLE ISOLATED AC VOLTAGE SPANS 0VAC TO 280VAC - Circuits designed by David A. Johnson, P.E.

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Circuits designed by David Johnson, P.E.

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Last Updated on: 06/17/2009 03:30:38 PM

Variable Power Supplies

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VARIABLE ISOLATED AC VOLTAGE SPANS 0VAC TO 280VAC
I designed and built this circuit about 25 years ago. It came in handy for many projects that were powered from 120 VAC, 240 VAC and 277 VAC. It provides complete isolation from the power line. It uses two 1:1 isolation transformers that are wired in parallel for the140vac range and in series for the 280vac range. The selector switch also diverts power to the appropriate output socket to avoid mishaps in sending the wrong voltage to the load. My home-built unit also included an AC volt and amp meter to monitor the output. However, this circuit only indicates the AC power connections.

Variable Power Supplies
Master Schematic Category List - David A. Johnson, P.E.