Influence of space harmonics on the permanent magnet linear synchronous motors performance

Speaking of linear machines, the waveform of the electromagnetic quantities is not sinusoidal, i.e. currents are not sinusoidal in time and magnetic field distributions are not sinusoidal in space, because of the asymmetry of both iron magnetic structure and windings. The performance of linear machines can be studied by means of one-dimensional or two- dimensional mathematical models. In both cases reliable results can be achieved only if the actual shape, or the harmonic content, of the electromagnetic quantities are considered and the models are able to handle space and time harmonics and their interaction. That increases the complexity of the linear machine model that must be used to obtain reliable results. Such models are very good tools for design purpose but can not be used in some applications, e.g. real time machine control, that require very short computation times. So a compromise between complexity and accuracy of the model must be achieved. That can be done by reducing the number of considered space harmonics and/or taking into account only the main space harmonics in order to simplify the model without significantly reducing the accuracy on the machine performance.