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A brushless excitation system model is set forth that includes an average-value rectifier representation that is valid for all three rectification modes. Furthermore, magnetic hysteresis is incorporated into the d-axis of the excitation using Preisach's theory. The resulting model is very accurate and is ideal for situations where the exciter's response is of particular interest. The model's predictions are compared to experimental results. Index Terms--Brushless rotating machines, magnetic hysteresis, modeling, simulation, synchronous generator excitation, synchronous generators.

In this paper, a parameter identification procedure for a recently proposed hysteretic brushless exciter model is discussed. The model features average-value representation of all rectification modes, and incorporation of magnetic hysteresis in the d-axis main flux path using Preisach's theory. Herein, a method for obtaining the model's parameters from the waveforms of exciter field current and main alternator terminal voltage is set forth. In particular, a genetic algorithm is employed to solve the optimization problem of minimizing the model's prediction error during a change in reference voltage level. Index Terms--Brushless rotating machines, genetic algorithms (GAs), magnetic hysteresis, measurement, parameter estimation, synchronous generator excitation.

This paper presents a design for a new dc brushless motor with an interior rotor for the cooling fan. The design differs fundamentally from conventional configurations using motors with exterior rotors, the difference being in the motor structure, where the arrangement for the rotor, the stator, and the blades in the fan gives the fan motor a higher stall torque, better efficiency, and reduced noise. The paper first models the fan motor analytically with an equivalent magnetic circuit, then develops a design to meet the desired performance, and follows with a finite-element analysis (FEA) for refinement and verification of this preliminary design. The FEA result confirms the accuracy of the analytical model. With other considerations such as the reduction of waste material taken into account, two other finite-element models are created, based on the foregoing design example, but with different parameters. The paper compares output characteristics of these three models to provide a brief reference for factors to be considered in motor design. Index Terms--DC brushless motor, equivalent magnetic circuit, fan motor, finite element.

This paper presents modeling and simulation of the operation of an 11-phase brushless exciter. The analytical method is based on Kron's tensor method, which is developed for dealing efficiently with the time-varying topology of an exciter circuit during a digital computer solution. The inductances, which are variable with rotor position, are calculated by the two-dimensional finite-element method. The detailed information (normal and fault cases) on the performance of the brushless exciter is obtained, which is beneficial to design engineers. The approach is suitable for both normal and fault cases. As a result, agreement of calculated values with test results shows the validity of the method of calculation and theoretical analysis presented. Index Terms--Brushless exciter, 11 phase, polyphase, polyphase brushless exciter.

The brushless doubly-fed machine (BDFM) has shown potential for adjustable speed drive applications. Although the BDFM is readily applicable for industrial drives requiring only slow speed response, control methods for higher performance operation need to be explored. With the help of a suitable synchronous reference frame dq model, this paper defines a BDFM synchronous angle and employs an electric torque estimator to establish a rotor flux oriented control algorithm. Experimental results show the effectiveness of the proposed controller. Index Terms - Doubly-fed machine, field orientation, microprocessor control, torque and speed control

Recent work has illustrated the potential benefits of brushless doubly-fed machines in adjustable speed drive applications. While it has been shown that the drive is open-loop stable over a wide speed range, the resultant steady-state and dynamic performance characteristics are far from optimum. Thus, a closed-loop controller is desirable to achieve competitive drive performance. The controller proposed here is applicable for general purpose industrial drives in the medium to high power range. The nature of the doubly-fed machine, with two separate sources of excitation, only one of which is controllable, rules out field-oriented control strategies applied to conventional induction machines. However, the concept of direct torque control based on instantaneous error shows promise for this machine geometry. The present paper extends the concept of predictive torque control for induction machines to the doubly-fed machine. The controller calculates the value of converter voltage which leads to desired changes of flux and torque. Once the voltage is determined, conventional algorithms, such as space vector pulsewidth modulation (PWM), can be used to generate the inverter switching function. Index Terms - Adjustable speed drives, doubly-fed machines, torque control, speed control.

Permanent magnet machines with trapezoidal back EMF waveform have been the subject of several papers in the past. The simplicity in control and the absence of an absolute position sensor makes this type of motor very attractive. Idealized analysis of such a machine is simple and will result in trapezoidal or square wave back EMF waveforms depending on the assumptions made. In the case of an idealized quasi-square wave current excitation, a ripple-free torque will be obtained. The actual back EMF waveform of these machines depends on the flux density and the conductor distributions. This in turn is a function of the magnet magnetization and the stator tooth and slot structure. In applications where a fairly smooth torque is needed, these machines are made with either the stator slots or the rotor magnets skewed by one slot. This paper deals with the analysis of the back EMF waveform and of the torque ripple waveform of such a machine when the stator slots or rotor magnets are skewed by one slot. The analysis takes into consideration the actual stator conductor distribution and the effect of magnet magnetization on the back EMF waveform. An empirical formula is developed for the magnet flux density distribution which could be used for various magnetization conditions of the magnet. Experimental results are included to confirm the analytical results.

A 2-d analytical model is developed for calculating the self- and mutual-winding inductances of brushless dc machines having surface-mounted permanent magnets and non-overlapping stator windings. The model is validated against both finite element analyses and measurements, and used to predict the influence of machine design parameters.

The mathematical modeling of a brushless DC generator is described, as an illustration of the application of diakoptic techniques to the analysis of small-scale electrical power supply systems. Modeling of the generator and its output rectifier is accomplished using an established matrix technique that accounts for the continuously changing conduction pattern of the diode bridge network. The advantages of using diakoptics are introduced when consideration is given to the main generator linked to its exciter and to the automatic voltage regulator and permanent magnet generator which are often included in a complete unit. A solution algorithm is presented for this overall arrangement and a comparison is made between theoretical and practical results for a typical 3-stage 4000 rev/min 10.3 kW 28 V unit.

An improved brusbless AC motor model is proposed for use in signal-injection-based sensorless control schemes by accounting for cross-coupling magnetic saturation between the d- and q-axes. The incremental self- and mutual-inductance characteristics are obtained by both finite-element analysis and measurements, and have been successfully used to significantly reduce the error in the rotor position estimation of sensorless control. Index Terms--Brushless AC motor, cross-coupling effect, sensorless, signal injection.

In this paper, a new multiphase polygonal-winding permanent-magnet brushless dc (PMBDC) machine is proposed and analyzed. The originality of the proposed machine lies on the multiphase polygonal-winding stator and the surface-inset permanent-magnet rotor. Because of its unique structure and operating principle, a circuit-field-torque coupled time stepping finite-element method is also employed for analysis. The designed machine is prototyped and the analysis is verified by experimentation. Index Terms--Brushless dc machine, permanent-magnet machine, time-stepping finite-element method.

A novel brushless ac permanent-magnet motor is described. This is intended for use as a highly efficient machine for a propeller-driven stratospheric aircraft. The machine is lightweight because of the use of plastics for the structural elements. A form of modeling is described in which the parameters for a decoupled equivalent circuit are calculated by three-dimensional finite-element analysis of a module of the machine. Matlab is then used to simulate the equivalent circuit action. It is shown that the fundamental component of the current waveforms agrees closely with a simple analysis approach. Index Terms--AC motors, finite-element methods, modeling.

An analytical model has been developed for calculating the open-circuit time-varying magnetic field distribution in the airgap/magnet/retaining sleeve region of a brushless permanent magnet motor equipped with diametrically magnetised magnets. It accounts for the stator slotting and curvature, as well as for parasitic eddy currents induced in the retaining sleeve and magnets. The analytically predicted time-varying field distribution in the different regions is compared with corresponding finite element predictions.

Finite element analysis is used to obtain the non-linear variation of axis and cross-axis flux-linkages for a dq model of an interior magnet, brush-less DC motor (BLDC). The model is used to compare competing designs of the conventional form of BLDC with designs of a novel type that has q-axis flux barriers. It is shown that the flux-barrier motor will give (i) equal rated performance, and (ii) better over-rating performance.

In this paper, robust position control of a direct drive using a state space model predictive control (MPC) algorithm is presented. The proposed controller consists of a state feedback regulator and a feedforward controller. Their gains are obtained by minimizing a cost function that is a sum of the position tracking errors and the control cost over some user defined time horizons. The effects of the controller parameters on the dynamic performance and the robustness of the direct drive are investigated. To provide good estimates of the state variables in the presence of load disturbance, a new observer based on the receding horizon concept is also formulated. Experimental results are presented to demonstrate the effectiveness of the approach. Index Terms--Brushless rotating machines, observers, predictive control, robustness.

A new permanent magnet (PM) brushless dc machine with a unique feature of flux regulation is proposed in this paper. The originality is that the air-gap flux of the machine is generated by both the PM excitation and the specially controlled stator current under the same PM pole. The machine possesses advantageous characteristics of both the PM brushless dc machine and the dc series machine. The rotor configuration and principle of operation are so novel that the magnetic field distribution and performances of the machine are analyzed by use of a time-stepping finite element method. The theoretical calculation is also verified by experimental measurement. Index Terms--Flux regulation, permanent magnet brushless dc machine, square wave, time-stepping finite element method.

Torque-ripple control of the brushless dc motor has been the main issue of the servo drive systems in which the speed fluctuation, vibration, and acoustic noise should be minimized. Most methods for suppressing the torque ripples require Fourier series analysis and either iterative or least-mean-square minimization. In this paper, a novel approach to achieve ripple-free torque control with maximum efficiency based on the d-q-0 reference frame is presented. The proposed method optimizes the reference phase current waveforms which include the case of three-phase unbalanced conditions. As a result, the proposed approach provides a simple way to obtain optimal motor excitation currents. The validity and practical applications of the proposed control scheme are verified through the simulations and experimental results. Index Terms--Brushless dc motor, maximum efficiency, optimal current, torque ripple.

This paper deals with the optimization of the design of electrical wheels. A new approach is used that generates the optimization software. It allows the design to be made with a more elaborate analytical model of the structure chosen for the wheel. Thus, it is possible to obtain a very efficient optimization program. This will be illustrated on the example of an electrical wheel for a bicycle. Keywords: Optimization methods, Brushless rotating machines.