Ian Malcolm wrote:

Backlash wrote:

I have a standard electrical outlet supplied by a 20 amp breaker,
outputting
118 volts. For something being planned, that circuit is needed to
output 125
volts at 20 amps capability. Is there a good method for this, and
what is
the most economical, feasable, and most practical method? It needs to be
fairly close to the 125 volt figure, as much as practical. Obviously, a
step-up transformer might be the solution, but what about the ability to
find one to output the 125 volts? Is there a practical homebrew buck and
boost method? I've done a decent amount of industrial, automotive, house
wiring and troubleshooting, but I'm a relative newby at this type of
theory,
so be gentle.

Thanks,
RJ


You only need a transformer to supply the difference (7 V) at 20 A.
6.3V should be near enough and some old gear had absolutely massive
transformers for the valve heaters. I dismantled some old test
equipment back in the 80's that had an 8A heater winding. Ask Gunner
if he's got any suitable transformers.

When you've got one, connect the secondary in series with the live
wire to the load and the primary accross the suppply. If the output
voltage is reduced from the input, reverse the secondary connections,
its phased wrong. Warning: you will draw approx 5% more current from
the supply than the load takes.

As a refinement you can use a small Variac (adjustable transformer) to
feed the 120 volt feed to
the 7 volt transformer. Variac's in the 3 Amp size are readily available.

Bill K7NOM