| Re: North London Line AC/DC question |
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Group: uk.transport.london · Group Profile
Author: Charles EllsonCharles Ellson Date: Jan 18, 2008 16:04
On Thu, 17 Jan 2008 15:44:51 -0800 (PST), D7666 hotmail.com>
wrote:
>< various snipped out >
>
>I don't know what the current limit relays were set at on 501s but
>being 4 motors per unit would be likely to draw more than a two motor
>2EPB.
>
>Published ''spotting book'' values of a 2EPB are 2x250 hp and 501
>4x185 hp so that makes a 501 in round figures 50%% more powerful than a
>2EPB - but I'd caution those numbers with similar comments I have made
>before about DC EMU in that the current limit relay setting needs to
>be known to understand peak current draw.
>
>As regards another part of the thread, I thought 2x313 operation was
>killed by platform length limits. 501 units were on 57 foot frames
>and platforms that could take 6cars laid out for that length - but
>could not take standard 6car sliding door trains with 20 m bodies.
>
>And I can't see why a 6car 313 would draw siginficantly more power
>than a 6car 501 to trip traction supplies. Again using ''spotting
>book'' values, without current limit values, a 313 has 8x82 kW motors
>that in round figures is 880 hp per unit - while a 501 is 740 hp.
>
>I would have expected the LNWR DC supply to have been a bit more
>robust than that as the overall load increase taking all traffic is
>not 20%% from a simple 313 and 501 comparison - but is Bakerloo+501
>c.f. Bakerloo+313 with the Bakerloo load unchanged.
>
>Must admit never thought about this aspect before, I might be wrong,
>its not a route thats easy to obtain gen on the traction supplies.
>
Don't the motor control systems of a class 313 present a more "peaky"
load than older stock ? This would in some way seem to be comparable
behaviour to computer switched-mode power supplies which blow plug
fuses if said fuses are rated purely on the current drawn after
switch-on. While I heard drivers allege that a 6-coach train tended to
trip sub-stations, I never heard any comment about being unable to fit
the trains in the stations which ISTR usually had about a
carriage-length to spare with c501s; when the 313s were first
introduced one difficulty was getting them to stop with any carriages
in the station and I don't think the cause was purely "driver
technique".
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