Electric Vehicle Propulsion Applications Research Articles

Mechanical Design and Analysis of a High-Torque Modular Hybrid Excitation Synchronous Machine for Electric Vehicle Propulsion Applications

Although hybrid excitation synchronous machines (HESMs) can provide an attractive flux-regulating capability, the fabrication and mechanical strength of the complex rotor are with significant challenges and need great efforts especially for high torque machines. In this article, a modular fabrication method of the dual-end magnetic-shunting rotor is proposed for high torque hybrid excitation synchronous machine. Then, by using numerical methods, the thermal stress of the rotor is calculated and compared with the 3-D FEA methods. To improve the mechanical strength of the rotor, the size of the screw, lug boss and filler is optimized, meanwhile, the rotor loss is optimized and thermal stress is evaluated. The results show that the proposed modular fabrication method demonstrates the improved mechanical strength and material utilization rate compared with the conventional fabrication process. Based on the three-dimensional finite-element analysis (3-D FEA) results, a 100 kW HESM prototype is successfully designed and manufactured using the proposed modular magnetic-shunting rotor. The experimental tests validate the effectiveness of the modular fabrication method and mechanical strength analysis.

Performance Comparison Study of Space-Vector and Modified-Carrier-Based PWM Techniques for a Three-Level Neutral-Point-Clamped Traction Inverter Drive

A performance comparison study between lower switching loss-based space-vector pulsewidth modulation (PWM) strategy for a three-level neutral-point-clamped inverter and a proposed modified-carrier-based PWM strategy is carried out for an electric vehicle propulsion application. The proposed carrier-based strategy uses single carrier and reduces the switching losses compared with the conventional carrier-based strategies by eliminating the common modulation interval between the upper and lower modulating signals. The inverter switching and conduction losses, total inverter loss, and voltage and current harmonic distortions are also compared with both the control strategies. PLECS is used to simulate the inverter losses with a 54-kW surface permanent magnet synchronous machine (SPMSM). Detailed simulation and experimental performances with the proposed carrier-based strategy and the dc-link voltage balancing during the change in speed and torque variations are carried out on a scaled-down prototype of 6-kW SPMSM. Dspace is used for hardware verification. Results show that, with the proposed carrier-based strategy, the dc-link capacitors are balanced even during the change in speed and torque.

Lithium−Air Battery: Promise and Challenges

The lithium−air system captured worldwide attention in 2009 as a possible battery for electric vehicle propulsion applications. If successfully developed, this battery could provide an energy source for electric vehicles rivaling that of gasoline in terms of usable energy density. However, there are numerous scientific and technical challenges that must be overcome if this alluring promise is to turn into reality. The fundamental battery chemistry during discharge is thought to be the electrochemical oxidation of lithium metal at the anode and reduction of oxygen from air at the cathode. With aprotic electrolytes, as used in Li-ion batteries, there is some evidence that the process can be reversed by applying an external potential, i.e., that such a battery can be electrically recharged. This paper summarizes the authors’ view of the promise and challenges facing development of practical Li−air batteries and the current understanding of its chemistry. However, it must be appreciated that this perspective ...

Comprehensive Efficiency Modeling of Electric Traction Motor Drives for Hybrid Electric Vehicle Propulsion Applications

Extensive research done in the recent past has proven that power electronic converters and electric propulsion motors are extremely critical components for modern hybrid electric vehicle (HEV) propulsion applications. Therefore, it is essential that both the traction motor and the associated drive operate at their optimal efficiencies throughout the driving schedule. In typical HEV propulsion applications, the traction motor and the drive are used over the entire torque/speed operational range. In view of this fact, this paper aims at modeling the inverter and motor losses/efficiencies over typical city and highway driving schedules. The noteworthy losses within a typical three-phase dc/ac traction inverter, such as the switching and conduction losses for both the insulated-gate bipolar transistors and the antiparallel diodes, are modeled and simulated over the city and highway driving patterns. An induction motor (IM) is used for a medium-sized sport utility vehicle, which was modeled in the advanced vehicle simulator (ADVISOR) software. The significant IM losses that were considered in the study include the stator copper losses, rotor copper losses, and core losses. Thus, the average efficiencies of both the inverter drive and the induction traction motor are evaluated and summarized under city as well as highway driving conditions. Finally, based on the individual-model-based efficiency analysis, the overall traction motor drive system efficiency is estimated.

Application of Direct-Drive Wheel Motor for Fuel Cell Electric and Hybrid Electric Vehicle Propulsion System

This paper presents a gearless wheel motor drive system specifically designed for fuel cell electric and hybrid electric vehicle propulsion application. The system includes a liquid-cooled axial flux permanent-magnet machine designed to meet the direct-drive requirements. The machine design implements techniques to increase the machine inductance in order to improve machine constant power range and high-speed efficiency. The implemented technique reduces machine spin loss to further improve efficiency. The machine design also optimizes the placement of magnets in the rotor to reduce cogging and ripple torque. An original cooling system arrangement based on the use of high thermal conductivity epoxy joining machine stator and liquid-cooled aluminum casing allows the very effective removal of machine power loss. Design details and experimental results are presented