Experimental investigation of the operating behaviour of linear synchronous motors

Linear machines can be derived from the various types of rotating synchronous machines.On the basis of cost, however, only the types having reaction systems (secondaries) without windings are suitable for high-speed vehicles. Of these types, the homopolar- machines and reluctance machines are distinguished by their simpler construction. In both of these cases, the reaction system consists of single ferromagnetic parts laid along the rail bed, e.g. in concrete.The primary carries the moving-field winding, usually 3-phase, and in the case of homopolar machines, also a d.c. excitation winding. With the linear reluctance machine, the disadvantages are that the thrust developed is relatively low, and that the magnetization current is taken from the grid. For this reason only the linear synchronous machine having homopolar constant field excitation can be considered as an alternative to the linear induction machine. In order to investigate the operating characteristics of high-speed machines of this type having a solid type of reactor, a model in the form of a sector machine was designed and built in the Department for Electrical Machines and Apparatus of the Technical University of Munich. The recently obtained experimental results are presented here.