Dissertation Hartmann

The aim of the present thesis, is the development of an analytical calculation method for the determination of the operational behavior of small electrically excited synchronous motors, which are driven by an inverter. The analytical calculation model considers all harmonics of the air-gap field except of harmonics that are caused by the magnetic saturation of the motor. Harmonics that are caused by the inverter are also considered.

The parameters of the synchronous motor are modeled according to a one-dimensional field approach. The influence of the variation of the permeance of the air-gap because of the slotting of the stator and the pole-gaps of the rotor is accounted for by relative permeance functions. To determine the parameters of the relative permeance functions analytical and numerical methods can be used. For this purpose, appropriate methods are presented in the thesis. Saturation effects of the iron of the synchronous motor are considered by an average saturation factor, which is only determined by the no-load saturation characteristics of the machine. Different switching states are obtained for the power electronics depending on if it is a squarewave or sinewave drive. For each of this switching states corresponding voltage equations are derived. The switching elements are considered to be ideal.

Another focus of this thesis lies on the systematic design and analysis of fractional slot windings. Special attention is paid to single-layer distributed fractional slot windings.

To validate and verificate the analytical calculation method, three different validation samples of the same size, but with different topologies, were available. With the proposed analytical calculation method, the operational behavior of small inverter fed electrically excited synchronous motors can be determined in a relative short period of time. The largest deviations between the analytical calculation method and numerical simulations or measurements are about 7%.