This paper presents a comprehensive overview of the latest studies and analyses of the cooling technologies and computation methods for the automotive traction motors. Various cooling methods, including the natural, forced air, forced liquid and phase change types, are discussed with the pros and cons of each method being compared. The key factors for optimizing the heat transfer efficiency of each cooling system are highlighted here. Furthermore, the real life examples of these methods, applied in the latest automotive traction motor prototypes and products, have been set out and evaluated. Finally, the analytical and numerical techniques describing the nature and performance of different cooling schemes have been explained and addressed. This paper provides guidelines for selecting the appropriate cooling methods and estimating the performance of them in the early stages of their design. Index Terms-Automotive applications, cooling, traction motors, thermal analysis, numerical analysis. NOMENCLATURECross section area of heat path (m 2 ). , Linear current density (kA/m). , Inlet and outlet cross section areas (m 2 ). Specific heat capacity (J/kg). Diameter (m). , Friction loss factor (dimensionless). Gravitational attraction force (m/s 2 ). Grashof number (dimensionless). Fin extension (m). ℎHeat transfer coefficient (W/m 2 K). ℎLatent heat (kJ/kg). Loss coefficient (dimensionless).

Switched Reluctance Motor (SRM) drives conventionally use current control techniques at low speed and voltage control techniques at high speed. However, these conventional methods usually fail to restrain the torque ripple which is normally associated with this type of machine. Compared with conventional three-phase SRMs, higher phase SRMs have the advantage of lower torque ripple: to further reduce their torque ripple, this paper presents a control method for torque ripple reduction in six-phase SRM drives. A constant instantaneous torque is obtained by regulating the rotational speed of the stator flux linkage. This torque control method is subsequently developed for a conventional converter and a proposed novel converter with fewer switching devices. Moreover， modeling and simulation of this six-phase SRM drive system has been conducted in detail and validated experimentally using a 4.0-kW six-phase SRM drive system. Test results demonstrate that the proposed torque control method has outstanding performance of restraining the torque ripple with both converters for the six-phase SRM, showing superior performance to the conventional control techniques.

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Linear Ramp Slope Compensation (LRC) and Quadratic Slope Compensation (QSC) are commonly implemented in peak current mode controlled DC-DC converters in order to minimize subharmonic and chaotic oscillations. Both compensating schemes rely on the linearized state-space averaged model (LSSA) of the converter. LSSA ignores the impact that switching actions have on the stability of converters. In order to include switching events, the nonlinear analysis method based on Monodromy matrix was introduced to describe a complete-cycle stability. Analyses on analogue controlled DC-DC converters applying this method show that system stability is strongly dependent on the change of the derivative of the slope at the time of switching instant. However, in a mixed-signal controlled system, the digitalization effect contributes differently to system stability. This paper shows a full complete-cycle stability analysis using this nonlinear analysis method, which is applied to a mixed-signal controlled converter. Through this analysis, a generalized equation is derived that reveals for the first time the real boundary stability limits, for LRC and QSC. Furthermore, this generalized equation allows the design of a new compensating scheme which is able to increases system stability. The proposed scheme is called Polynomial Curve Slope Compensation (PCSC) and it is demonstrated that PCSC increases the stable margin by 30% compared to LRC and 20% to QSC. This outcome is proved experimentally by using an interleaved DC-DC converter that is built for this work.

Segmental rotor Switched Reluctance Machines (SRMs) have been demonstrated to produce more torque than toothed rotor SRMs because each coil is able to link more magnetic flux. This paper considers a six-phase segmental rotor SRM and compares it to a conventional SRM with the same lamination length and outer dimensions. Both fully-pitched (FP) and single-tooth wound (STW) motor configurations of the segmental rotor SRM are investigated. The FP winding machine produces higher torque than the single tooth winding machine when using the same phase conduction angles but has unacceptably long end windings. Optimized conduction widths and current shapes are subsequently applied to the single tooth winding segmental rotor SRM. The segmental SRM is shown to produce about 10% higher rated torque, with less core loss and copper loss than the conventional SRM throughout the whole speed range.