On Jul 25, 11:36*am, D7666 wrote:
On Jul 25, 4:38*am, Andy wrote:

*A more powerful modern traction system doesn't
necessarily generate twice as much heat just because it has twice as
much power at its disposal.

I^2*R still applies.

Power (w) = Volts (V) x Amps (A)

Same 630 V voltage applied, double the power = double the current.

Double the current and the heating effect in all conductors goes up 4
times.

That is one of the laws of electricity.

Either you are continuing to suggest - as I have already commented -
the laws of phyiscs are suspended or you just plain do not understand
it.

No, you're missing the point, as far as I can make out.

If my excellent new power system gives me the *possibility* of using
1MW of power, when the previous power system only gave me the option
of 0.5MW, that says *absolutely nothing* about how much power (-
heat) I'm actually going to use.

And if the 1MW of power allows me to go from 0-90km/h in 20 seconds
instead of 40 seconds, then obviously the new train will be drawing
more power than the old train for the first 20 seconds... but then
it'll be in cruise instead of acceleration for the next 20 seconds,
and hence will be drawing much less power than the old train would, so
the total energy used won't be much different.

The actual *use of energy* will increase to match the higher rating of
the power system only if the power upgrade solely caters for increased
car weight, worse traction motor efficiency, more ancillary services,
etc, and doesn't actually improve acceleration.

--
John Band
john at johnband dot org
www.johnband.org