Basis Research On Segmented Switched Reluctance Motors

The segmented switched reluctance machine (SRM) consists of several independent stator ironsegments, or several rotor iron segments which are embedded in non-magnetic cover. Both of the twofeatures make it have the advantages of high fault tolerance, low wind (oil) resistance, and low ironloss at a high speed, besides the advantages of the conventional SRM like flexible control as well asadaptability of high temperature and speed. Thus, the segmented SRM has potential foreground inapplicable systems such as electro-mechanical actuation systems and starter/generator system in themore/all electric aircraft, electric/hybrid-electric vehicles and new energy system.This dissertation focuses on structure topologies of segmented SRM, electromagneticcharacteristics and electric machine design, fault diagnosis and fault-tolerant control of positionsignals, and the design of the experimental system.Firstly,2D and3D models of SRM with fully pitched windings and segmental rotor areestablished in order to analyse the static magnetic density distribution and calculate phase inductance.The computational formula of main body for SRMs with fully-pitched windings and segmental rotorscan be obtained when the currents in phase windings are equivalent to square waveforms. The rule ofselecting pole arcs of stator and rotor teeth for SRMs with fully-pitched windings and segmentalrotors is analyzed based on the electromagnetic performances of the motor, especially at alignedposition and unaligned position. The principles of calculating the number of turns of windings andother key dimensions of the motor are also established. A prototype is designed with the methodpresented, the finite element analysis and the experiments are accomplished. The results verify thisdesign method for SRMs with fully-pitched windings and segmental rotors.To solve the collision of the magnetic flux in the stator teeth of the four-phase8/6SRM withfully-pitched windings and segmental rotors, two new methods are proposed. One is that dividing themotor's stator and insulating them by magnetic spacers, the other is excitated with bipolar currents byfour identical H-bridges. Finite element instantaneous models of the two kinds of8/6segmented SRMare presented, to compare the electromagnetic feature of two kinds of motor's current, copper loss,iron core's flux density curve, iron loss.The existing segmented SRMs are overviewed based on the analysis of their constructions andmagnetic paths. Five novel segmented SRMs, which are toroidal-windings SRM with segmentalrotors, short-pitched windings SRM with segmental rotors, SRM with C-shaped segmental stators, SRM with E-shaped segmental stators and axial-radial air gap SRM with segmental stators, arepresented. The structures and the basic working principles of these five novel segmented SRMs areintroduced, and the advantages and disadvantages of them are also analyzed. All above will provide auseful reference for segmented SRM's researches and applications.3D model of SRM with E-shaped segmental stators is established and mutual inductances ofwindings are analyzed. The computational formula of main body for SRM with E-shaped stators isdeduced when taking each separate modular stator as a power unit. The principles of calculating thenumber of turns of windings and other key dimensions of the motor are also established. A machineprototype is designed, the electromagnetic performance is analyzed and the results verify thiselectromagnetic design method.The installation of position sensors is discussed and position deviations are measured by plusecurrent method. According to the analysis of the fault of position signals, a diagnostic method, whichdetects the edge sequences of position signals and calculates the angle between the adjacent edges ofposition signals is researched. Fault-tolerant control is carried out by taking advantage of the anglerelations of position signals. When the fault position signals restore, the wrong edges can be detectedand rejected by using this diagnostic method, and the motor can run steadily when the position signalrestores. The validity and feasibility of fault diagnosis, fault-tolerant control and fault recovery areverified by experiments.A digital control system for segmented SRM is designed and the softwares are completed basedon two different control strategies. The first strategy optimizes turn-on angle and turn-off angle, aswell as adjusting current limits; The second strategy optimizes turn-off angles and adjusts turn-onangle according to speeds. Finally, the characteristics of two control strategies are analyzed andverified by experiments.