> The presumption was, I think, that the motor power consumption was a
> constant, not that the amperage drawn was constant. In other words,
> the motor is a 24 volt motor, and it draws 25 amps, in contrast with
> a 12 volt motor that draws 50 amps.
>
> In reality, I think Harry's motor has somewhat more power than the
> 12 volt motor, but not twice as much, so the real numbers might be
> something like 12v, 50 amp vs 24v, 30 amp.
>
> --
> Kent Crispin "Do good, and you'll be
> kent@songbird.com lonesome." -- Mark Twain
>
>
> Ohms Law and Circuit Fundamentals says, to wit
> !hp=746 watts expended assuming 100% efficieny
> Amps= watts divided by the Voltage....I=P/E
> Watts=E times I
[...]
Yes, I'm familiar with this stuff. Please note that I said that the
*power consumption* was held constant between the two motors, *not*
that the two motors are the same. They are not the same: one has a
*design voltage* of 24 volts, and the other has a *design voltage* of
12 volts. Under those circumstances, neglecting inefficiencies of
various kinds, the current draw of the first motor would be half the
current draw of the second motor.
To rephrase the original point, neglecting inefficiencies, for a
constant power draw, twice the batteries should give you
approximately twice the run time. However, Harry's motor is
somewhat more powerful, though not twice as powerful, as I recall.
> ....So...the motor is an inductive
> device and limits it`s wattage/horse power by
> a phenomenom known as reactance or XL
> So, double it`s design voltage and in most
> cases it shortly over heat and burn up.
As noted, nobody was talking about doubling a design voltage.
> Some motors are designed for variable
> voltage (sewing machine motor) they can do
> this because the design allows the motor to
> change speed with a voltage change and the
> power utilization rate remains the same
> (or close enough) The laws that govern this
> are seldom what we want or need and cannot
> be changed. (The above is peculiar to DC
> circuits)
> Regards....Bill p15 #2001
> "Small Wonder"
>
>
>
-- Kent Crispin "Do good, and you'll be kent@songbird.com lonesome." -- Mark Twain