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.


Any what is the resistance of said conductors in a 2009 stock train
compared to a 1967 stock? Plus the effect of the 750V power supply
which you've already mentioned. You seem to keep thinking that the
innards of the 2009 stock will be the same as the 1967 stock.

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 are the one who doesn't understand, you seem to be fixated on
the current consumed. Power is not the problem, current is not the
problem. How much of the energy consumed goes to waste heat, rather
than moving the train is the problem. You don't seem to grasp the idea
that electrical machines in general have got considerably more
efficient in the last 40-45 years.

The current used by the system is NOT the amount of waste heat
generated by the train. You keep mentioning the power consumption, but
this has nothing directly to do with the amount of waste heat
generated by the trains (for a given design it will be related of
course, but not between designs). I have never said that the trains
will be consuming less power, just trying to point out that the power
will be used much more efficiently in a modern electrical system than
it was in a 1960s design.

You need to recognise the difference between nominal power rating of
the motors (the kW consumed) and the amount of that power which is
converted into kinetic energy by the drive train? Can you say what
the electrical efficiency of the 2009 stock is compared with the 1967
stock, if you can't then your power ratings are useless when looking
at energy wasted. I'm willing to bet that the 2009 stock is
substantially more electrically efficient than the 2009.

All this is on top of the difference in heat generation between the
rheostatic brakes on the 1967 stock compared to regenerative brakes on
the 2009 stock. The Victoria line should be good for regeneration, as
the service is frequent and so braking trains will usually find the
line receptive to the energy being produced, with another train
accelerating out. Indeed the constant constant current AC motors will
be much better in this regard than the DC motors.

I give up.