[Captain Howdy]

Alright with that said and with your degree in Electrical
Engineering this shouldn't be hard. All you need is a regulated power supply,
any cheesy amplifier will do, although an unregulated amplifier will show
clearer results. Run a low test tone into the amplifier with a dummy load on
it at 14.5 volts and at 10.5 volts and watch the current draw. The tick here
is to keep the same output voltage on the amplifier at both input voltages.
See what happens to the current draw. And you're right about the dual voltage
motors, they achieve their dual voltage capability via alternate wiring in the
motor.



In article om, "D.Kreft"
wrote:
On Feb 26, 3:37 pm, (Captain Howdy) wrote:

Have you not ever hooked up a dual votage electic motor, if you ever come
across one see the amp specs at 110v and at 220v, Whoever told ya that this
only works when transforming or inverting was just trying to mess with your
mind.

I'm not an electric motor expert, but I do hold a degree in Electrical
Engineering (I suppose that one could argue that my EE profs were all
out to mess with my mind). Granted, I'm not an EE by profession, but I
do have enough edukashun and real-world experience with electronics to
have something of a clue as to how these things work.

From what I understand about dual-voltage electric motors, they
achieve their dual-voltage capability via alternate wirings in the
motor itself or via an internal transformer (such as would be found in
a computer power supply or home electronics box) which is used to
convert the to the desired level. Some devices, like laptop computer
power converters do this voltage sensing automagically so that you
don't have to flip as switch as you would on a typical desktop
computer power supply or home audio receiver.

So even here, you're still talking about using a transformer to handle
the voltage conversion. The reason that a doubling of input voltage
results in a halving of input current is simple--because assuming
negligible losses in in the transformer itself the law of the
conservation of energy (from the first law of thermodynamics) applies:

Pin = Pout

Substituting VI (voltage * current) for each side:

Vin * Iin = Vout * Iout

Then divide both sides by Vin:

Vout * Iout
Iin = -------------
Vin

So yeah, doubling Vin leads to a halving of Iin. There's nothing new
here.

Ultimately, though, we're still dealing with DC inputs so this
comparison to dual-voltage AC motors, while entertaining, isn't
entirely relevant and does more to support my point than detract from
it.

-dan