1. Usable electrical principles

It's easy to see that "linear" railways have tried almost everything in the way of electric propulsion, replacing, on the track, rotary motors which have become variable-frequency and drive axles and wheels (with adhesion) either directly, or by generalized gear reduction. After a century of ideas, tests and... 5 achievements in commercial service worldwide, in 2008 as far as we know, there are only two motorization principles currently in use, on or off the track. Both use the latest models of static converters (with GTO or IGBT) designed for "rotary" applications:

• on the one hand, mobile inductor circuits with small or unvarying air gaps (e.g. 1 cm), compared with track-mounted armatures;

• on the other hand, inductor circuits on the track, with larger and more variable air gaps (1 to 10 cm, for example),...