Multi-phase motors have several advantages over the traditional three-phase motors. In this study, the additional degrees of freedom available in five-phase permanent magnet motors have been used for three purposes: 1) enhancing the torque producing capability of the motor, 2) improving the reliability of the system, and 3) better adjusting of the torque and flux linkages of the five-phase direct torque controlled system. 1) Due to the fact that space and time harmonics of the same orders will contribute positively to output torque, a five-phase permanent magnet motor with quasi-rectangular back-EMF waveform is supplied with combined fundamental and third harmonic of currents. For modeling and analysis of the motor a 0 3 3 1 1 q d q d frame of reference is defined where 1 1q d rotates at the synchronous speed and 3 3q d rotates at the three times synchronous speed. Based on the mathematical model in the 0 3 3 1 1 q d q d frame of reference, it is shown that this system while having a higher torque density with respect to a conventional permanent magnet synchronous machine, is also compatible with vector control algorithm. 2) A resilient current control of the five-phase permanent motor with both sinusoidal and trapezoidal back-EMF waveforms under asymmetrical fault condition is proposed. In this scheme, the stator MMF is kept unchanged during healthy and faulty condition. Therefore, the five-phase permanent magnet motor operates continuously and steadily without additional hardware and just by modifying the control algorithm in case of loss of up to two phases. The feature is of major importance in some specific applications where high reliability is required. 3) High torque and flux ripple are the major drawbacks of a three-phase direct torque controlled system. The number of space voltage vectors directly influences the performance of DTC system. A five-phase drive, while benefiting from other advantages of high order phase drives, has inherently 32 space voltage vectors which permits better flexibility in selecting the switching states and finer adjustment of flux and torque. A sensorless direct torque control of five-phase permanent magnet motor is implemented. Speed information is obtained based on the position of stator flux linkages and load angle. Experiments have been conducted on a 5kW five-phase surface mount permanent magnet motor and a 3kW five-phase interior permanent magnet motor by using TMS320C32 DSP. The results obtained are consistent with theoretical studies and simulation analysis, which further demonstrate the feasibility and practical significance of the five-phase permanent magnet motor drives.

This thesis deals with the design of a five-phase machine. In the first part of this thesis are presented theoretical knowledge about five-phase machines. In the next part of the thesis is designed five-phase machine by analytical calculation according to selected parameters. This calculation includes the resulting load and start characteristics. The geometrical parameters of the machine are transferred to the Ansys program, where the finite element calculation is performed together with the required simulations. The results are compared and commented.

Multiphase machines have gained a lot of popularity during the recent years, as they offer certain benefits over their three- phase counterparts. This work investigates the losses of a six- phase drive system for a marine application when supplied by four different switching patterns (also referred to as modulators). Using MATLAB/SIMULINK, a model was built for the machine featuring three independent frames and a nonlinear, cross coupled flux relation. It has been connected with the corresponding modulator models, where two carrier based modulators have been developed as well as two space vector modulators. The simulation data was then fed into the loss model to calculate the corresponding losses in both machine and converter. This work shows that control of the harmonics – mainly the fifth – is beneficial to reduce losses, mainly in the machine. Without control, harmonic currents cause unnecessary losses. As none of the investigated modulators strictly dominates all others, this work suggests a combination of the two carrier based methods to create a simple and robust modulator, which offers both a high voltage magnitude and control over the fifth harmonic. / Flerfasmaskiner har blivit mycket populära under dem sestate åren, då de erbjuder specifika fördelar jämfört med trefasmaskiner. Denna avhandling undersöker förlusterna för en sexfasmakin för en maritim applikation när den är kopplad med fyra olika modulatorer. En modell för maskinen byggdes i MATLAB/SIMULINK som innehåller tre oberoende nivåer samt en ickelinjär och korskopplad flödesrelation. Maskinmodellen har blivit kopplad till de fyra korresponderande modulatormodellerna, där två är baserade på bärvågor samt de resterande två är baserade på rymdvektormodulation. Data erhållen från den simulerade maskinmodellen var sedan inmatad in i en förlustmodell för att beräkna de korresponderande förlusterna för både maskinen och omvandlare. Denna avhandling visar att kontroll av övertoner – i huvudsak den femte övertonen – är fördelaktigt för att minimera förluster, främst i maskinen. Eftersom ingen av de modulatorerna som undersöktes i avhandlingen är bäst i alla funktioner, föreslår avhandlingen en kombination av de två bärvågsberoende metoderna. Den nya modulatorn antas vara bra både i kontrol över den femte övertonen men också erbjuda en hög spänning tack vare hamonisk injektion. Dessutom är modulatorn enkelt och robust, eftersom det är bärvågberoende.