We recently received some messages from Geoff Thorne, the technical leader for a restoration project at the London Transport Museum. They are restoring several electric motor cars from the 20's and 30's. The London Underground will soon be raising the voltage from 600V to 750V, so they need to insure that the old equipment will work reliably at the higher voltage. The electrical systems were supplied by British Thomson Houston, a subsidiary of GE, and they use GE DB-260 contactors. From the pictures, they look to me just like the contactors on the 319 and 431.
Geoff wanted to know if we have any technical data for these contactors, in particular, what the specs might be for the interlocks, things such as the minimum separation. I'll ask around here, but if anyone has any GE data sheets for these contactors, or knows where to look, it would be much appreciated.
He sent us some pictures of the cars being restored, known as "Q stock":
These cars do not run in the Tube, but they use the same four-rail power system. There is an outside third rail for positive traction power, and a center fourth rail for the negative return. This system was designed because of the signalling requirements for the complex layout of London Transport, and signalling is much easier if you don't have traction current flowing through the running rails, as we do at IRM, for instance.
As I say, these contactors look very familiar.
This is obviously an automatic acceleration system. Many of the interlock contacts have to open under load. (By "load" I mean the control circuit current, of course, on the order of 1A, not the traction power!) So it's important to have a sufficient opening distance.
This locomotive, #12 Sarah Siddons, was built in 1922 and is still used for occasional fan trips. Like everything else, its electrical systems need to be upgraded. This is also a good picture of the four-rail track system.
For comparison, this is what modern Tube cars look like, because they have to fit into a 12' diameter tube. The museum also has some historic Tube cars which they plan to restore for operation, perhaps next after the Q stock cars are finished.