Novel synchronous machines: linear and disc

The author considers some of the developments that have taken place over the last few years in the field of synchronous machines of unusual geometry. Linear synchronous motors are a comparatively new development; they have the virtue of considerable higher force production but require a variable frequency supply. However, in small sizes, power integrated circuits have become available that can be used to power the machines as brushless DC drives. A tubular version using permanent magnet excitation is described. The development of disc brushless alternators is also described. In these machines the excitation winding is located on the same side of the air-gap as the AC winding. A demonstration of the use of the new `high´-temperature superconductors, which uses a double disc form of these machines, is outlined