Re: SLR - Extension construction

[matthew@mail.usyd.edu.au (Matthew Geier)]

In article <lj5qiskbv0u1gkg6kuovq90u698hb35aj7@4ax.com>,
Bill Bolton <billboltonREMOVE-TO-EMAIL@computer.org> wrote:
>neumannc <neumannc@ozemail.com.au> wrote:
>
>> The airconditioning load on the variotrams is quite high as a proportion
>> of the total electrical load of the tram (ditto for tangaras).  The
>> "natural" air conditioning of the North Sydney trams did not require
>> electricity!
>
>The current drain of just one coupled set of O Class cars climbing
>from water level to the top of the ridge, as they did all along the
>Eastern end of the North Sydney system, would easily account for more
>current than two Variotrams on the lightly graded SLR.
>
>> North Sydney also had extensive feeders.
>
>And much lighter gauge trolley wire than the SLR.
>

 But the simple cam-shaft controls on the old trams would be very tolerant
of voltage fluctuations. Those coupled O's probably would have still run
up those grades with 150v or more loss on the overhead.
 Modern trams with their many Kw of auxillaries might not be so forgiving.
 The A and B class trams in Melbourne have a current-limit switch that basicly
stops one tram from pulling to much power and affecting others. One driver
commented that the flicking that switch affected how quickly they could
accellerate, and that he never used it. 

 A Variotram might still move with 150v drop (down to 500v on the line) but I
wouldn't mind betting that the air-conditioning and the salon lighting would
shutdown in an effort to reduce the load.

 They can't have the AC and lights dropping out on every tram on the extension
each time one puts on a spurt of accelleration.

 Ill try and get a closer look at the extension trolley wire and work out its
diameter and then lookup the voltage drop characteristics for copper wire of
that diameter. That will be a best case, the trolley wire will be alloyed to
make it harder and less ductile, and that will have a adverse affect on the
conductivity.