The paper deals with the problem of force and torque calculation for linear, cylindrical and spherical electromechanical converter.

The electromagnetic field is determined analytically with the help of separation method for each problem. The results obtained can be used as test tasks for electromagnetic field, force and torque numerical calculations. The analytical relations for torque and forces are also convenient for analysis of material parameters influence on electromechanical converter work.

The paper concerns the problem of choosing a criterion for transmission line when lumped parameters analysis is required. First, the formal introduction of transmission line scheme is presented. Secondly, a new criterion for lumped-parameter analysis of transmission line is proposed. The criterion has clear physical meaning and simple mathematical form. The proposed criterion takes into account not only wave length, but also the dissipation of transmission line. The criterion can be easily adjusted to some requirements, such as needed level of no-load output voltage change.

The paper deals with the problem of electromagnetic field analysis for linear, cylindrical and spherical electromechanical converters at synchronous state of work. There are considered synchronous motor with windings on moving part (rotor, carriage) and with permanent magnets thereon. The electromagnetic field is determined analytically with the help of separation method proposed for each problem. The boundary conditions are formulated for electromechanical converters linear, cylindrical and spherically shaped. The results obtained can be used as benchmark for electromagnetic field numerical analysis and force/torque calculations.