Re: Fate of 85/86 class

["Greg Hunter" <huntergpmj@bigpond.com>]

Maurie Daly <mauried@commslab.gov.au> wrote in article
<mauried.411.38A2A112@commslab.gov.au>...


> 
> Heres an interesting question.
> For Electric hauled coalies coming down the Blue Mtns from Katoomba to 
> Emu Plains are just about continuously regeneratively braking,ie putting
back 
> power into the overhead , does RAC pay freightcorp a credit for this 
> electricity.
> I betcha not.


No not an explicit credit but then they don't pay an explicit amount for
what they use either - just a fixed fee per trip.  It's impossible to
figure out how much regen is actually used by other trains rather than
being wasted in resistor banks.  And how much is it worth to the buyer
anyhow?  
The complications of two operators (SRA & FC) either powering or regening
and resistor banks are impossible to meter unless you have time stamped
meter readings an each meter on each train and you know where the trains
were at all times.

And by using regen they save a lot in brake shoes.

The braking resistors cannot handle the power regened by 4 locos anyhow.

> 
> On a similar vein,do 25KV /AC locos regenerate power back into the
overhead
> and if so how is it done?

When you go to AC induction motors on the locos, regen is easy and
virtually free.  The basic loco circuit has a transformer to step down the
25 kV to some intermediate voltage (1000-2000). Then a controlled rectifier
to give an intermediate dc voltage, then inverters for the motors.  These
inverters control the voltage and frequency to the motors.  To make an
induction  motor regen you just need to run the inverter at a slightly
lower frequency that the motor is turning at.  This gives you dc back out
and the controlled  rectifier can be easily made to inverted back to AC.

Greg

Greg