The Swiss Electric-Steam Locomotives

A unique- and apparently lunatic- locomotive scheme was to generate steam by electric heating. This appears to make no sense; you don't need Denver Lasik to to be able to see why, after having gone to all the trouble and expense of electrifying a railway line, it seems counter-intuitive to then use that electricity to run a steam engine with its less-than-impressive efficiency, rather than simple electric motors. Although patent offices are filled with strange, head-scratching inventions, this one in particular seems a bit demented.

It was not. There was (as usual) a good reason. In fact, it was actually a pretty clever solution to a temporary problem.

Left: Article from The Electrical Magazine: 1904

The article above shows that the possibility of using hydro-electric power to boil water in a locomotive had ben considered for a long time. The article's date is only known to be between January and June 1904.

Left: One of the Swiss electric-steam tank engines The Swiss Federal Railways had a highly electrified system during the Second World War, but retained little 0-6-0 tank engines for shunting. Due to war conditions coal was in short supply, but hydro-electricity remained plentiful. Therefore some of these small steam locomotives were converted to raise steam by electric heating. Power was taken at 15 kV, 16.6 Hz from overhead lines by a pantograph, and fed to resistance heating elements in the boiler, via two transformers rated together at 480 kW. Water feed was by normal steam injectors. These unique locomotives also retained the capability of being fired by coal in the usual way.

Left: Another view of the electric-steam tank engine Weight was increased by 7 tonnes to 42 tonnes so new springs were fitted. The savings were 700 to 1200kg coal a day. 300kg steam at 12 bars per hour could be generated. The heaters were the two boxes on the frame ahead of the coal bunker. The water was pumped from the boiler low point through the heaters and back into the boiler. Startup from cold took only 1 hour, as a small coal fire was kept going. The costs for the conversion was 100,000 Swiss Franks per Engine. Electric lighting was fitted, with a battery charged from the overhead wire.

Left: And another view. The chimney seems to have been extended in this photo When I first published this page I found it strange that power was distributed at such a low frequency; one obvious objection to 16.6 Hz distribution is that all the transformers would be three times the size of those for a conventional 50 Hz system. The answer is that due to the state of electric motor technology at the time, electric locomotives used serial wound commutator motors as traction motors. They were essentially DC motors running on AC. Without using electronics, it is difficult to control the speed of an AC induction motor. As Fehér Tamás, one of my correspondents, put it: "About 18Hz is the highest frequency where sturdy-built DC electric motors can be run safely with minor modifications. There will be occasional sparks and arcs at the commutators, but it is tolerable. Go over 20 Hz and you will have frequent circular-fire shorts on the current feed brushes, quickly destroying the motor." I would like to thank all those who wrote in to point this out to me, and I can offer my apologies for taking so long to update this page.

Left: This is engine E 3/3 pictured in 1942.

Left: This was clearly taken at the same time as the picture above.

Left: Preserved, without electric heaters One of these locomotives (No 8522) is preserved, although it has lost its electric heating system. It is kept at this museum in Switzerland, associated with the Sursee-Triengen railway.

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