Search

This paper presents a method for estimating the machine parameters of a synchronous motor. The presented method is equally applicable for a wound field synchronous motor, synchronous reluctance motor, or permanent magnet (PM) synchronous motor, both the interior and surface-mount types. The method works particularly well for machines having a significant amount of space harmonics, such as synchronous reluctance and interior PM (IPM) machines, where the harmonics are predominantly the slot harmonics. It is also well suited for surface PM machines operating under saturation, where the harmonics are saturation-induced. The presence of these harmonics makes the parameter identification difficult. Most of the methods presented so far in the literature have failed to properly identify machine parameters in the presence of space harmonics. In this paper, the machine parameters, identified by using a proposed algorithm, are compared with the finite element and the experimental results to demonstrate the effectiveness of the presented method. Both interior PM and surface PM machines are considered. Index Terms--Parameter identification, synchronous machine.

This paper presents a lumped-parameter thermal model for a multi-barrier interior PM synchronous machine. The model consists of a network of 12 thermal resistances that make it possible to estimate temperatures at 9 critical points inside the machine including the stator end windings, rotor magnets, and the bearings. The details of the model are presented and two machines are analyzed, including a 6 kW 12-pole automotive starter/alternator and a 0.5 kW 4-pole electric water pump machine. The lumped-parameter model results for both machines demonstrate good agreement with results obtained using detailed thermal finite element analysis. Index Terms--AC machines, brushless machines, equivalent circuits, losses, optimization methods, permanent magnet machines, synchronous machines, thermal factors.

THis paper presents a design methodology for digital proportional-integral current regulators that may be used for the highly nonlinear switched reluctance motor control. The important nonlinear behavior of saturation, back electromotive force (EMF), and mutual coupling are accounted for to achieve consistent current regulator performance over the entire operating regime. Gain adaptation is used with respect to both position and current to insure stability. An improved back-EMF decoupling scheme is implemented to reduce bandwidth requirements. The proposed control is implemented on a high-torque traction drive for electric vehicle applications. Simulation and experimental results demonstrate excellent performance over the entire operating regime. Index Terms--Digital control, mutual coupling, proportional-integral (PI) current regulator, switched reluctance (SR) motor.

A high-density and high-efficiency switched reluctance (SR) motor has been designed and built for vehicle propulsion. Extensive finite-element analyses have been carried out to optimize the geometry for high density. Steady-state performance of the drive has been simulated to ensure good efficiency at all speeds. Special attention has been given during machine design to lower the acoustic noise. Direct liquid cooling of the winding has been designed to improve the machine overload capability. Dyno test results are presented which show good overall performance of the SR drive for vehicle propulsion. Index Terms--Electrical drives, switched reluctance (SR) machine.

A high-performance fully digital controller has been designed for the control of a switched reluctance (SR) motor built for vehicle propulsion. The SR machine is specifically designed and built to have high density and low noise. The controller is designed to maximize the machine efficiency, the peak overload capability, and to minimize torque ripple at low speed. Lookup tables are stored in a digital-signal-processor-based controller to calculate the control parameters online. Three interpolations, between torque command, motor speed, and battery voltage, are performed to obtain the control parameters. Difficulties associated with the interpolation scheme are addressed. A high-bandwidth fully digital proportional plus integral current regulator has been designed for the control of the phase current. Advantages as well as the difficulties with the operation of the SR machine and its control have been addressed. A complete characterization of the controller for the entire torque-speed plane has been made through extensive dyno testing. Simulation and dyno test results have been presented to demonstrate the performance of this controller. Index Terms--Digital control, electrical drives, switched reluctance machine.

This paper presents a simple on-line rotor time constant identification scheme of an indirect field-oriented induction motor for the purpose of improving the performance and robustness of the drive. The proposed technique neither requires any special test signal nor any complex computations. This scheme is based on a special switching technique of the current-regulated pulsewidth modulation (CRPWM) voltage-source inverter (VSI), which allows measuring the induced voltage across the stator phase. The rotor time constant is then identified directly from this measured voltage. This proposed technique provides six windows within one electric cycle to update the rotor time constant, which should be sufficient for all practical purposes. Simulated results followed by experiments are presented to validate the effectiveness of the proposed technique.

There is a growing interest in electric and hybrid-electric vehicles due to environmental concerns. Recent efforts are directed toward developing an improved propulsion system for electric and hybrid-electric vehicles applications. This paper is aimed at developing the system design philosophies of electric and hybrid vehicle propulsion systems. The vehicles' dynamics are studied in an attempt to find an optimal torque-speed profile for the electric propulsion system. This study reveals that the vehicles' operational constraints, such as initial acceleration and grade, can be met with minimum power rating if the power train can be operated mostly in the constant power region. Several examples are presented to demonstrate the importance of the constant power operation. Operation of several candidate motors in the constant power region are also examined. Their behaviors are compared and conclusions are made. Index Terms - Electric vehicle, hybrid electric vehicle, motor drives, road vehicle electric propulsion, road vehicle propulsion.

We compute complex modes in lossless shielded asymmetric coplanar waveguides (CPW's) using the spectral domain technique. The slot asymmetry is found to significantly affect the existence of the complex modes. These modes are found to exist at low microwave frequencies even when using materials with a low permittivity. We found that waveguide modes degenerate into complex modes more frequently than CPW ([Pi]) and slotline (c) modes. When the structures are highly asymmetrical and when the dielectric substrates are thick or have a high permittivity, the degeneration of lower-order c-modes into complex modes is detected. Other forms of mode conversion, where a waveguide mode is converted to a c-mode, are also observed, especially in highly asymmetric structures and when using dielectric materials of a high permittivity or of a large thickness. Numerical convergence of the complex modes' propagation constants is also examined.

Single- and multiple-step discontinuities for a shielded three-layer coplanar waveguide (CPW) are studied. The mode matching procedure is employed to obtain the scattering (S) parameters of the discontinuities. The analysis is validated through a comparison of the calculated S-parameters of a single step discontinuity for a shielded single-layer CPW and those published previously. Calculated S-parameters for various single, double, and triple step discontinuities are presented. Effect of the modal orthogonality criterion on the discontinuity S-parameters is given. Extensive investigation of the numerical convergence of the S-parameters is also described.

An extensive analysis, based on a full-wave mode-matching technique, is described for coplanar strips (CPS) incorporating the strips' finite metallization thickness. Results for the effective dielectric constant and characteristic impedance are presented to show the effect of the metallization thickness. It is found that the characteristic impedance has a strong dependence on the metallization thickness, which signifies the fact that the finite metallization thickness needs to be considered in designing practical microwave circuits employing CPS. Numerical results of CPS with zero metallization thickness obtained using this method are found to be in good agreement with those published previously. Extensive investigation of the numerical convergence of these results is also described.

Switched reluctance motor (SRM) optimal control parameters, which maximize torque per ampere, are calculated using a dynamic SRM model. In order to include the effect of the magnetic nonlinearity, static torque and flux-linkage data are used in the dynamic model. The static data are generated experimentally. To recreate these control parameters, online, artificial neural networks are used. Two separate networks are trained. One is trained with the low-speed control parameters for torque control at low speed, while the other is trained with the high-speed control parameters for torque control at high speed. The speed at which the SRM makes a transition from chopping control to single-pulse operation (i.e., low-speed to high-speed operation), commonly referred to as base speed, is torque (current) dependent. A small table is maintained in the controller to identify the base speed for different torque demands. When the motor exceeds the base speed for a certain torque demand, the controller switches from the low-speed neural network to the high-speed neural network and vice versa. It is also shown that the SRM is capable of producing an extended constant-horsepower operation with this optimal control. The power factor (the energy ratio) is shown to improve in this extended speed constant-horsepower range. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed control scheme. Index Terms--Electrical drives, neural network control, switched reluctance machine.

Soft switching has the potential of reducing switch stresses and of lowering the switching losses as compared to hard switching. For this reason, several soft-switching topologies have been presented in the literature. Each topology has some advantages. Their operation, however, requires additional active and/or passive elements. This introduces additional cost and complexity. To understand the effectiveness of the soft-switching technique, when applied to electric vehicle (EV) and hybrid electric vehicle (HEV) systems, it may be necessary to first evaluate their system requirements and performance. This evaluation process would require knowledge of the vehicle dynamics. The vehicle load requires a special torque-speed profile from the drivetrain for minimum power ratings to meet the vehicle's operational constraints, such as initial acceleration and gradability. The selection of motor and its control for EV and HEV applications are dictated mainly by this special torque-speed requirement. As a consequence, this requirement will have a strong influence on the converter operation. This paper makes an attempt to evaluate EV and HEV running in both standard Federal Test Procedure 1975 city driving and highway driving cycles. A simplified analysis will be carried out for several of the most commonly used electric motors operating on the optimal torque-speed profile. Special attention is given to the converter conduction and switching losses. By analyzing the switching losses, and by assuming that an ideal soft-switching scheme will have zero switching losses, one can evaluate the improvement in the system efficiency if a soft-switching control is used. The relative significance of soft switching for EV and HEV systems will then be established. Index Terms--Electric vehicle/hybrid electric vehicle soft-switching evaluation, soft-switched electric vehicle/hybrid electric vehicle motor drives, soft switching.

Land vehicles need their drivetrain to operate entirely in constant power in order to meet their operational constraints, such as initial acceleration and gradability, with minimum power rating. The internal combustion engine (ICE) is inappropriate for producing this torque--speed profile. Therefore, multiple gear transmission is necessary with the ICE in a vehicle. Some electric machines, if designed and controlled appropriately, are capable of producing an extended constant power range. The purpose of this paper is to investigate the capabilities of the switched reluctance motor (SRM) for electric vehicle and hybrid electric vehicle applications. This investigation will be carried out in two steps. The first step involves the machine design and the finite-element analysis to obtain the static characteristic of the motor. In the second step, the finite-element field solutions are used in the development of a nonlinear model to investigate the dynamic performance of the designed motor. Several 8-6 and 6-4 SRM geometries will be investigated. Effects of different stator and rotor pole widths and pole heights on the steady state as well as on the dynamic performance of the motor will be studied. The air gap for each motor will be made as small as manufacturally possible. The aspects of performance to be compared for each design motor are: 1) the range of the constant power operation; 2) drive efficiency in this extended constant power range; 3) the power factor in this operational range; and 4) the short time overload capability. The first performance index defines the rated power of the motor. The longer the constant power range, the lower is the power rating for the same vehicle performance. Hence, special emphasis will be given to this. In the high-speed operation of the SRM, there will be considerable phase overlapping. Hence, thicker back iron than usual might be needed to prevent the back iron from saturating. However, since flux peaking of each phase occurs at different rotor positions, the phase overlapping might not necessitate special designing of the back iron. However, the possibility of the back iron being saturated will not be neglected and will be investigated. The optimal control parameters of the SRM, which maximize the constant power range with maximum torque per ampere, will be calculated. A performance comparison will be made for this optimal operation. Simulation results of the designed SRM will be presented for vehicle acceleration. To demonstrate the capability of the SRM in producing an extended constant power range, experimental results will be presented, however, for a reduced size motor available commercially. Index Terms--Constant power range, electric vehicle, hybrid electric vehicle, switched reluctance motor drive.

A sensorless field oriented control scheme for surface mount permanent magnet ac (PMAC) motor with split phase stator windings is presented. This motor is obtained by splitting the phase windings of a conventional three phase motor. The six-phase motor, however is run as a three-phase motor by connecting the split phase stator windings in series, while the taps are made available for voltage measurements. By measuring the terminal voltages and the line currents, absolute position of the permanent magnet ac motor driven by a current regulated PWM inverter with a hysteresis controller is estimated. The estimated position information is independent of the stator resistance, thus this scheme is even applicable at low speeds. Results are presented to show the effectiveness of the new controller, and it is also shown that the position error is negligible.

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. [ABSTRACT FROM AUTHOR]

This paper presents an algorithm to calculate the current references on line, considering the inherent nonlinear nature of the saturation effect in an interior permanent-magnet synchronous machine for the minimum-copper-loss control under the current and voltage limit of the drive system. This paper basically approaches this issue as a nonlinearly constrained Optimization problem where the torque command imposes the nonlinear equality constraint and the voltage limit imposes the nonlinear inequality constraint. Depending on the operating region, it solves the corresponding set of nonlinear equations in real time derived from the Lagrange multiplier method. Newton's method among various techniques is adopted to implement the numerical solution. This scheme gives accurate results not only in motoring but also in generating operation of the machine, since the voltage drop of the stator resistance is taken into account, which is hardly applicable to a two-dimensional lookup table where the inputs are the torque command and the maximum flux amplitude, and the output is each axis current reference in the rotor reference frame. The simulation and experimental results show the feasibility and performance of the proposed technique. [ABSTRACT FROM AUTHOR]