Re: One Railway to order 20 new 100mph EMUs for 2009

On Jun 29, 1:20 pm, David Jackman <pleasereplytogroup> wrote:
"R.C. Payne" <r...@xxxxxxxxxxxx> wrote innews:f62p1l$e5f$1@xxxxxxxxxxxxxxxxxxxx:



MIG wrote:

...

Everything new seems to be 100 mph these days (apart from the 376s,
surprisingly). They evidently want nippiness, with the top speed
providing flexibility if they cover anything else.

Except that nippiness is what a lower top speed gives you. If you are
geared for 75mph, you will have much better acceleration from a
standing start than geared for 100mph. It may be that the
characteristics of the ac power electronics (rather than good old
fashioned dc motors) may make this redundant, I'm just a mechanical
engineer, and don't understand all this electrickery.

Robin

The game has changed.

A half-decent 1st generation EMU - lets take a 308 as typical - had 4,
200hp motors giving a total of 800hp (574 kW). A Clacton unit had
higher power motors - total 840 kW. After an aberration with the 315s
(eight low power motors, total 657 kW when all working) the next
generation doubled the power available; a 321 packs 1072 kW.

The current generation has something approaching twice as much power
AGAIN. The 360 has two power cars, each with four motors. Platform 5
are quoting the motors as 250 kW each while Siemens quote 1550 kW at
wheel.

It is very sad to see such thoroughbreds (OK, the DC version) pottering
round the Hounslow loop to schedules slower than the stock they replaced
... but for real Desiro action Germany is the place to be. The DB
version packs 2350 kW at wheel in a four car articulated formation.
These do 0-90 mph in 60 seconds... We have nothing like that in this
country (but it would be very useful in keeping GE stoppers out of the
way of Norwich fasts).

It isn't electrickery. It's brute force with some sophisticated
electronics to avoid wheel spin.

David


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