A gas turbine driven, high-speed, high-efficiency generator system intended for use in series-hybrid vehicles is developed. It consists of a permanent-magnet (PM) generator and a rectifier. The eddy-current loss in the magnets of the high-speed PM generator may be problematic. Therefore, a model of the PM machine including this loss in the magnets due to the time harmonics of the stator currents is introduced and verified. This loss can be represented by magnet loss resistances in the equivalent circuits. It can be decreased by using smaller magnets or by using sinusoidal stator currents.

The aim of the research project this paper arises from, is the development of a high-speed, high-efficiency generator system for use in series-hybrid vehicles. This paper describes an analytic method for the two-dimensional calculation of the magnetic field in the cylindrical air gap of the permanent-magnet generator. Further, it introduces a method to visualize this field, namely by plotting the lines of constant magnetic vector potential. To show that the calculated magnetic field may form the basis of a machine model, the voltage equations are derived. The proposed analytic method gives insight into the relations between dimensions and parameters of the machine, which is important when optimizing the design.

A generator-converter unit, consisting of a high speed permanent magnet generator and a high frequency cycloconverter, is developed. The generator-converter unit is intended for use in total energy systems connected to the utility grid, or hybrid systems in vehicles, or vessels. It will be driven by a high speed high efficiency gas turbine. The advantages of this variable speed constant frequency (VSCF) system, such as optimal turbine speed and small size and weight, are discussed. The 6-pulse cycloconverter, used to change the 800 Hz generator frequency to 50 Hz, is described in detail. A new combination of control methods results in a substantial improvement of the power factor load of the generator. Individual pulse control of the cycloconverter by means of digital signal processing results in excellent control properties of the generator-converter unit. Measurements are given on a 50 kW experimental system, consisting of a 600 Hz test generator and a single phase cycloconverter.

A 6-pulse noncirculating current cycloconverter is used as frequency changer for a high-frequency permanent magnet generator. A high-efficiency, high-speed gas turbine in the power range of 250 kW to 870 kW, drives the generator-converter unit. This system is intended for use in total energy systems or hybrid systems in vehicles and high-speed vessels. The cycloconverter is designed for three-phase 833 Hz to 50 Hz applications. A new vector-control like digital control strategy and a special discrete Fourier filter (DFT), intended for use with a one-phase version of the cycloconverter, are described. Both are implemented in a multi-processor digital controller used for feedback control and pulse-pattern generation. Simulation results and measurements of a laboratory one-phase version of the converter and a dummy-generator, using this digital control strategy and DFT, are given.