Ian P. Brown

Comparative Study of Interior Permanent Magnet, Induction, and Switched Reluctance Motor Drives for EV and HEV Applications

With rapid electrification of transportation, it is becoming increasingly important to have a comprehensive understanding of criteria used in motor selection. This paper presents the design and comparative evaluation for an interior permanent magnet synchronous motor (IPMSM) with distributed winding and concentrated winding, induction motor (IM), and switched reluctance motor (SRM) for an electric vehicle (EV) or hybrid electric vehicle (HEV) application. A fast finite element analysis (FEA) modeling approach is addressed for IM design. To account for highly nonlinear motor parameters and achieve high motor efficiency, optimal current trajectories are obtained by extensive mapping for IPMSMs and IM. Optimal turn-ON and turn-OFF angles with current chopping control and angular position control are found for SRM. Additional comparison including noise vibration and harshness (NVH) is also highlighted. Simulation and analytical results show that each motor topology demonstrates its own unique characteristic for EVs/HEVs. Each motors highest efficiency region is located at different torque-speed regions for the criteria defined. Stator geometry, pole/slot combination, and control strategy differentiate NVH performance.

Modeling and analysis of effects of skew on torque ripple and stator tooth forces in permanent magnet AC machines

In this paper, simplified FE-based modeling and analysis of torque ripples in permanent magnet ac machines is presented. The electromagnetic torque is calculated based on the virtual work principle, where field quantities are evaluated using a minimal number of nonlinear magnetostatic finite element solutions. A simple and fast method of incorporating the effects of the stator and/or rotor skew in the torque calculation is introduced. The proposed method requires a minimum number of 2-D finite element evaluations to estimate the electromagnetic torque profile of the skewed machine at a given load condition. This is especially beneficial for rapid evaluation of the effects of stator and/or rotor skew in large-scale design optimization studies. A fast method of evaluating stator tooth forces using a Maxwell stress tensor approach applied to the field quantities calculated using minimum number of 2-D magnetostatic finite element solutions is introduced. Finally, effects of the skew on the developed tooth forces are evaluated.

Influence of Parallel Paths on Current-Regulated Sine-Wave Interior-Permanent-Magnet Machines With Rotor Eccentricity

The behavior of rotor eccentricities in current-regulated interior-permanent-magnet machines is investigated. The study focuses on two typical topologies of significant industrial relevance: machines with distributed windings with two slots per pole and phase and motors with concentrated coils and three slots per pole pair. The effect of stator-winding parallel paths is examined for both cases. Coil and terminal electrical quantities and radial forces were simulated using finite-element analysis. Unbalanced operation, where the currents are not equal in parallel phase connections due to eccentricity, is also investigated. Experimental measurements of electrical quantities and forces on motors with static eccentricity are carried out using two special test setups. The experimental measurements validated the simulation results.

Observer-based inverter disturbance compensation

Most inverter disturbance compensation methods are based on open-loop inverter disturbance estimation. Because of measurement error and switching device parameter uncertainties, the inverter disturbance is not always compensated well. This paper proposes a closed-loop voltage disturbance observer and an observer-based inverter disturbance compensation method to improve the compensation. The performance and limits of the voltage disturbance observer and compensation system are analyzed in detail. Analytical and experimental results are provided to verify the performance. The results are particularly relevant when the inverter is used to inject signals for self-sensing.

Electromagnetic and vibrational characteristic of IPM over full torque-speed range

This paper investigates the electromagnetic and vibrational characteristic of an interior permanent magnet machine (IPM) over the entire torque-speed range based on the model of 2004 Toyota Prius IPM motor. First, the dominant electromagnetic radial force directly causing vibration is calculated based on optimal operating plane, which covered by maximum torque per ampere (MTPA), current limit curve, and maximum torque per volt (MTPV) curve. Next, vibration behavior of the stator is studied by using modal and structural analysis in ANSYS workbench environment. It is observed that electric vehicle (EV) application deserves closer attention as more resonant vibration points may appear. To simultaneously meet the efficiency and NVH (noise vibration and harshness) requirements the pole-slot number and control strategy should be carefully chosen.

Design of a wound field synchronous machine for electric vehicle traction with brushless capacitive field excitation

This paper describes the modeling, optimization, mechanical design, and experimental characterization of a high power density wound field synchronous machine (WFSM) for electric vehicle traction applications. The WFSM is designed for brushless rotor field excitation using an axial flux hydrodynamic capacitive power coupler (CPC). A flexible design environment is described which was used for large scale multi-objective optimization. A prototype WFSM, spray cooled with automatic transmission fluid (ATF), with an 80 kW (peak) output at a base speed of 4,000 RPM has been tested. The prototyped WFSM achieves peak volumetric and specific torque and power densities of 17.22 Nm/l, 4.69 Nm/kg, 7.19 kW/l, and 1.95 kW/kg.

Unbalanced operation of current regulated sine-wave interior permanent magnet machines

The behavior of rotor eccentricities in current regulated interior permanent magnet (IPM) machines is investigated. The study focuses on two typical topologies of significant industrial relevance, i.e. machines with distributed windings with two slots per pole and phase and motors with concentrated coils and with three slots per pole pair, respectively. The effect of stator winding parallel paths is examined for both cases. Coil and terminal electrical quantities, radial forces, and torque ripple were simulated using FEA. Unbalanced operation, where the currents are not equal in parallel phase connections due to the eccentricity, is also investigated. Experimental measurements of electrical quantities and forces with static eccentricity are carried out with two special test fixtures. The experimental measurements validated the simulation results.

Induction machine design methodology for self-sensing: Balancing saliencies and power conversion properties

Zero-to-low-speed flux/rotor-position self-sensing techniques rely on the interaction of saliencies (asymmetries) with an injected signal or special switching pattern in the inverter to produce a response which contains information about the location of the saliency. In this paper, three types of deterministic spatial rotor position saliencies are introduced into an induction machine (IM). The saliencies were created by modulating the following: 1) the rotor bridge opening width; 2) the rotor bridge opening height; and 3) the rotor bridge opening fill. The influence of saliency geometric design variables on the self-sensing and power conversion properties is determined using a design of experiments and response surface methodology. An example IM design, which maximizes the self-sensing properties while preserving power conversion abilities, is presented. Modulation of the rotor bridge fill appears to be the least desirable saliency type. Both rotor bridge opening width and height modulations can be used successfully, but the rotor bridge opening width modulation requires extra simulations to characterize the self-sensing properties.

Synchronous generator field excitation via capacitive coupling through a journal bearing

Wound field synchronous generators (WFSG) are the standard for back-up and utility scale power generation. Rotor field current and prime mover speed are the only control parameters required to regulate power conversion in a generator application. Maintenance costs may be minimized by adopting non-contact or “brushless” technologies to replace sliding slip ring connections. This paper presents a brushless excitation approach using ceramic insulated sleeve (journal) bearings with oil lubrication to form capacitively coupled slip rings, in contrast to more traditional inductive brushless exciters and rotary transformers. This capacitive power transfer (CPT) approach exhibits advantages including low weight, low volume and has a relatively simple construction using off-the-self components. Analysis, design and prototype construction of the CPT system are presented. Experimental results demonstrate that ∼1.7nF of capacitive coupling transfers 340W to the rotor field winding of a 10kW 208V WFSG. Voltage regulation of a WFSG is demonstrated during steady state and 1 per unit load step changes yielding a NEMA-MG1 class G2 rating.

Design and evaluation of interior permanent magnet compressor motors for commercial transcritical CO 2 (R-744) heat pump water heaters

This paper describes the design and experimental evaluation of two high efficiency interior permanent magnet (IPM) motors for use in a commercial transcritical CO2 (R-744) heat pump water heater (HPWH). Two IPM topologies, 36 slot 6 pole and 9 slot 6 pole, were selected, optimized, and prototyped using a common, flat bar interior permanent magnet rotor. The experimental analysis includes standard measurements of electrical machine quantities, and light load dynamometer tests. Initial measurements of the CO2 compressor and HPWH system performance with a stock line fed induction machine have been completed.