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Through analytical equations followed by a systematic optimization study using high-fidelity finite-element (FE) models, the torque capability of three common synchronous machine technologies—namely, a permanent magnet (PM) synchronous machine (PMSM) with V-shaped rare-earth rotor magnets, a PMSM with deep V-shaped ferrite rotor magnets, and a synchronous reluctance machine (SynRM) with four layers of conforming flux barriers are compared for an application in a 48-V mild hybrid electric car. The optimization of the deep V-shaped ferrite PMSM automatically resulted in a spoke-type PM layout for maximum torque production. Yet, an optimized SynRM with conforming flux barriers was achieved that could produce a higher torque than ferrite PMSM. One machine technology is selected and six variants of it, with two rotor PM layouts each with three alternative pole-slot combinations, are subsequently subjected to a large-scale FE model-based drive-cycle design optimization. Various pole-slot combinations are methodically compared in terms of drive-cycle losses, active material cost, torque ripple, and PM demagnetization level. More than 20 000 designs were analyzed over ten energy-centric torque-speed points to identify an optimal design solution. The results of multiphysics analysis incorporating electromagnetics, computational fluid dynamics, and structural analyses are provided, including a study on three different water jacket concepts. A final design is prototyped and primary experimental results are provided.

The design and optimization procedure of two different types of PM-assisted synchronous reluctance machine (PMASynRM) made of different types of PMs: Ferrite and NdFeB will be proposed in the paper. The two different types of PMASynRM are designed for the traction application and will be compared to a two-layer V-type IPM with NdFeB magnets only, which is used as the baseline design. The proposed two different types of designs have the same stator geometry and winding configuration as the baseline design. The main purpose in the paper is to reduce NdFeB PM content by investigating and comparing two different types of blended design PMASynRM, namely, a parallel hybrid design and a series hybrid design. The key challenges when reducing the rare-earth content are: (1) Maintaining the same rated torque as the baseline (2) Reducing even eliminating the risk of demagnetization due to the lower coercivity of ferrites at both low and high temperature. In the paper, we will focus on the comparative analysis of two different types of PMASynRM by means of the presented optimization process with emphasis on assessing the level of permanent demagnetization risk. In order to assess the structural integrity of the rotor, a mechanical analysis was conducted in parallel design. The proposed parrel design can generate competitive torque as the baseline design with around 25% reduction of rare-earth material while eliminating the demagnetization risk at the extreme low operating temperature of -20°C and high temperature of 150°C. The paper includes details of the optimization process and corresponding sample results, evaluation of demagnetization risk of both types of PMASynRM designs, and analysis and optimization results of both types of designs.

A large-scale finite element model-based design optimization algorithm is developed for improving the drive-cycle efficiency of permanent magnet (PM) synchronous machines with wide operating ranges such as those used in traction propulsion motors. The load operating cycle is efficiently modeled by using a systematic k -means clustering method to identify the operating points representing the high-energy-throughput zones in the torque–speed plane. The machine performance is evaluated over these cyclic representative points using a recently introduced computationally efficient finite element analysis, which is upgraded to include both constant torque and field-weakening operations in the evaluation of the machine performance metrics. In contrast with the common practice, which aims at enhancing the rated performance, the entire range of operation is considered in the present design optimization method. Practical operational constraints imposed by the voltage and current limits of the motor-drive system, excessive PM demagnetization, and torque ripple are accounted for during the optimization process. The convergence to the optimal design solutions is expedited by utilizing a new stochastic optimizer. The developed design algorithm is applicable to any configuration of sinewave-drive PM and synchronous reluctance motors over any conceivable load profile. Its effectiveness is demonstrated by optimizing the well-established benchmark design represented by the Toyota Prius Gen. 2 interior PM motor configuration over a compound operating cycle consisting of common U.S. driving schedules. Multiphysics electromagnetic, thermal, and mechanical performance of the optimized design solutions is discussed in a postdesign optimization stage.

Through a systematic optimization study using high-fidelity finite-element (FE) models, torque capability of three common synchronous machine technologies, namely a permanent magnet (PM) synchronous machine (PMSM) with V-shaped rare-earth (RE) rotor magnets, a PMSM with deep V-shaped ferrite rotor magnets, and a synchronous reluctance machine (SynRM) with four layers of conforming flux barriers are compared for an application in a 48-V mild hybrid electric car. The optimization of the deep V-shaped ferrite PMSM automatically resulted in a spoke-type PM layout for maximum torque production. Yet, an optimized SynRM with conforming flux barriers was achieved that could produce a higher torque than ferrite PMSM. One machine technology is selected and is subsequently subjected to a large-scale FE model-based drive-cycle design optimization. Various pole-slot combinations are methodically compared in terms of drive-cycle losses, active material cost, torque ripple, and PM demagnetization level. More than 20,000 designs were analyzed over ten energy-centric torque-speed points to identify an optimal design solution. The results of multi-physics analysis incorporating electromagnetics, computational fluid dynamics (CFD), and structural analyses are provided, including a study on two different water jacket concepts. A final design is prototyped and initial experimental results are provided.

The demand for increased power and improved fuel economy are driving changes in alternator technology for automotive applications. To meet these demands requires a drive system with capabilities of torque assist, regenerative braking, and power generation to supply vehicle loads while keeping the battery charged. Furthermore, to minimize add-on cost, the system must be air-cooled and operate at 12V with the same or smaller packaging footprint of the current alternator. In this paper, a low cost 12V 4kW air-cooled IPM drive system for automotive electric power management is presented. The design and analysis in terms of machine, inverter, controller and control algorithm are discussed in detail. Thermal performance of system under different operating conditions are studied. Finally a prototype drive system was built and tested and found to meet the cost, performance and packaging requirements.

The demand for increased power and improved fuel economy are driving changes in alternator technology for automotive applications. To meet these demands requires a machine with capabilities of torque assist, regenerative braking, and power generation to supply vehicle loads while keeping the battery charged. Furthermore, to minimize add-on cost, the system must be air-cooled and operate at 12V with the same or smaller packaging footprint of the current alternator. In this paper, two low cost 12V 4kW air-cooled PM-assisted synchronous reluctance machine designs for automotive electric power management are presented. The design and analysis in terms of electromagnetic, mechanical and thermal behaviors are discussed in detail. One of the machines was built and tested and found to meet the cost, performance and packaging requirements.

Future automobiles will be equipped with x-by-wire systems to improve reliability, safety, and performance. The fault-tolerant capability of these systems is crucial due to their safety critical nature. Three fault-tolerant inverter topologies for permanent magnet brushless direct current motor drives suitable for automotive x-by-wire systems are analyzed. A figure of merit taking into account both cost and postfault performance is developed for these drives. Simulation results of the two most promising topologies for various inverter faults are presented. The drive topology with the highest postfault performance and cost effectiveness is built and evaluated experimentally.

Future automobiles will be equipped with by-wire systems to improve reliability, safety and performance. The fault tolerant capability of these systems is crucial due to their safety critical nature. Three fault tolerant inverter topologies for permanent magnet brushless dc motor drives suitable for automotive x-by-wire systems are analyzed. A figure of merit taking into account both cost and post-fault performance is developed for these drives. Simulation results of the two most promising topologies for various inverter faults are presented. The drive topology with the highest post-fault performance and cost effectiveness is built and evaluated experimentally.