Life is always interesting and today whilst discussing electric railways I came across the concept of saline solution resistance controllers of 3-phase motors.
It started off with a description being given of two electric wires above an electric railway which happened to be the still-born Porthmadog, Bergellert and South Snowden Railway – a power and railway company that attempted to connect the then North Wales Narrow Gauge Railway with Porthmadog in 1904. It will hopefully soon form part of the rebuilt Welsh Highland Railway – the original (W.H.R.) company was a successor to the P.B.&S.S.R.
From the description of the overhead, I recognized a corner grounded ac delta system (Gantz System I think after the Hungarian promoters) and this proved correct. It was however the description of the motors which left me curious. They were described as slip-ring induction motors with control resistors comprising copper rods dipped in a saline solution. As the rods were dropped further into the liquid, the resistance became less (as the motor accelerated) until zero resistance was facilitated by a dead short. Mention was made about the solution being part of the central ‘star’ of the motor windings which confused me further (the supply is delta).
It all seems a rather odd setup to have in an electric locomotive. Can anyone please elaborate?
[This message has been edited by Hutch (edited 07-15-2004).]
