Various industrialized structures
Linear and compound electric motors

There are generally three basic structures of the open magnetic circuit motor:

• linear motor (one mechanical degree of freedom) ;

• linear rotation (two mechanical degrees of freedom) ;

• spherical (three or more degrees of freedom).

The motor with short double armature and non-magnetic armature, most often operating as an asynchronous converter, forms the most general class of linear machines: figure 18 shows an industrial series of this type...