RE: A 48 VOLT FREEWAY EV?

[eric.chang@chrysalis.org]

>The only real problems (that I see) with 48V setups are: three times the
>I2R losses; your cables have to handle three times
 
At three times the current, the I2R losses would be 9X for the same
wire thickness.  As for the motor being 3X heaver, that is not
quite correct.  The scaling is such that the length of the wire
decreases with it's increase in thickness, so the losses stay the
same, and the amount of copper stays the same.  Reference: earlier
discussions on rewinding motors.
 
Another way to look at it is with multiple motors.  Running two
motors in series at 100 volta and 100 amps is very similar to
running them in parallel at 50 volts and 200 amps.  The power
output is the same, and the I2R losses are *also* the same.  You
may say that doubling I has increased losses by a factor of 4,
but if you look very carefully, R has not been decreased by a
factor of 2.  (It has been decreased by a factor of 4.)
 
Eric