Talk:Bruce Peebles Electric Locomotives
Add topicThe August 2011 edition of 16mm Today, carried an article by Stacey Baker on the construction of models of these locomotives. Therefore it was of interest to read your article on these locomotives. For a start it has answered my question as to the reason for the 2 collector poles. The fact that these locos operated on a 3-phase supply, has answered this.
I would like to expand a little on the control of 3-phase locos. They are still used in Switzerland and until recently on the Italian main lines. 3 phase traction tends to operate at a speed fixed by the supply frequency. By having multiple pole motors, it is possible to provide 2 or even 3 fixed speeds. Once up to the synchronised speed, should the train tend to over-speed, the motors would become generators and provide the necessary braking effect to regulate the speed.
As for starting, Electrolytic Starters, usually containing sodium carbonate solution were in common use. I had experience of them in use on large 750kW fan motors until the 1990's when displaced by more modern electronic variable speed drives. They are still used in certain applications. They are used to control the starting current of an electric motor by varying the resistance by moving an electrode into the tank of electrolyte progressively during the starting period. Once the motor is running, (typically measured in seconds)the starter is by-passed. I presume that when these locos were built, the starting was manually controlled. As long as the driver/motorman operated the starter over the required period, the electrolyte should not have overheated and boiled. Problems would arise if the starter was left in an intermediate position. These were starting devices, not speed controllers.
Paul Kidger
Have you got the name of the author of the article correct? I have not seen it so do not know myself but I imagine it might be Stuart Baker. THe reason for suggesting that the electrolyte might boil came from Rodney Weaver who had witnessed similar motors in use in the Blaenau quarries. There the motors were being used much more frequently than they were designed to do and a stream was apparently diverted into the electrolyte tank to keep it cool. As you say, used properly they should not have overheated but I imagine there would always have been the temptation to add another coach or two.