Minimum torque ripple, maximum efficiency excitation of brushlesspermanent magnet motors

Permanent magnet motors are usually driven in one of two ways. Sinusoidal currents are applied when the motor has a sinusoidal back EMF, and rectangular currents are applied when the back EMF has a trapezoidal shape. If implemented perfectly, each of these drive schemes is capable of producing ripple-free torque, which is desirable in many applications. However, in reality, permanent magnet motors never exhibit perfectly sinusoidal or trapezoidal back EMFs. Moreover, the power electronics used to drive the motor often has limitations that keep it from producing the required current waveform, especially as speed or load torque increases. In addition to these limitations, a permanent magnet motor often exhibits parasitic cogging torque that directly contributes to torque ripple. This work explores the relationships between motor current and back EMF, and identifies minimum torque ripple, maximum efficiency current excitations that can be implemented with finite bandwidth power electronics (current controlled VSI)     

Pulse motor with high-temperature superconducting levitation

A simple but stable noncontact high T_c superconducting levitation system with a vertical shaft has been presented. The system consists of a superconductor and permanent magnets. In the system, only a high T_c superconductor supports the lower end of the shaft, and the other end is supported by two ordinary permanent magnets. Since the restoring force is small with respect to the radial direction, the system becomes unstable when the force acts in the radial direction, so it is difficult to drive the shaft by electromagnetic forces when using motors. A driving system using electromagnets has been presented, in which the balanced forces act on two opposite sides of the disc-type rotor in the axial direction. Since the system has no unbalanced force from an analytical point of view, the rotor will be able to rotate without control. In the system, however, since there is eccentricity between the center of rotation and the magnetic center, vibrations are generated. This study also presents an optimal control method for the vibrations. To validate the proposed system and the control method experimental tests have been carried out     

Permanent magnet pulse motor with high temperature superconductinglevitation

A simple but stable noncontact high T_c superconducting levitation system with a vertical shaft has been presented. The levitation system consists of a superconductor and permanent magnets. In the system, a high T_c superconductor supports a lower end of the shaft, and a pair of permanent magnets supports the other end. Although a levitation is stable when the levitation system is used, since the restoring force is small in the horizontal direction, the levitation stability is small in the horizontal direction. Hence, it is difficult to drive the shaft by electromagnetic forces in using such motors. This paper describes a driving system consisting of six coils and a permanent magnet with eight poles, in which balance forces act on two opposite sides of the disc type rotor in the axial direction. The system has no unbalance force, and stable rotation is obtained without control. To validate the proposed system, experimental tests have been carried out. The experimental motor achieved stable rotation at speeds up to 1250 rpm     

Internal Permanent Magnet Motor Design for Electric Vehicle Drive

Power compaction and high efficiency are two key advantages of permanent magnet motors. This paper proposes an enhanced internal permanent magnet motor that delivers high torque, power compaction, and exceptionally high efficiency in the same operation area. The advantage of the proposed scheme is the magnetic flux accumulation in the air gap, which allows much higher values of magnetic flux density, compared to a surface permanent magnet motor of the same size. The original contribution of this paper resides on the adopted motor configuration, enabling to efficiently utilize the energy stored in the permanent magnet and to provide total loss minimization at the most frequently used speed range.     

Design of a fault-tolerant IPM motor for electric power steering

This paper deals with the design of an interior permanent magnet (IPM) motor for power steering. Such an application requires an imperative fault-tolerant capability that is obtained by means of a redundant solution with two motors on the same shaft. A ball-screw system converts the rotating movement into the linear movement of the steering rack. In addition, the IPM motor has to exhibit very low braking torque after a short-circuit fault. Useful relationships between the maximum braking torque and the motor parameters are found and used in the design of the motor.     

永磁同步电机的弱磁控制方法

永磁同步电机（PMSM）是最流行的电机,例如作为高速电动列车的牵引电机,源于其高转矩电流比的特性和能够通过弱磁控制扩大恒功率区域的能力,矢量控制理论的发明是交流调速领域中的一个重大突破,文中将详细讨论永磁同步电动机的矢量控制,在推导其精确数学模型的基础上分析了矢量控制理论用于永磁同步电动机控制的几种电路控制策略,包括了id=0控制,最大转矩/电流控制,最大输出功率控制,最小磁链转矩比控制,最大电压转矩比等.     

Optimization of a synchronous reluctance machine for a sensorless drive with a wide field-weakening range

For more than one century, electrical machines have been utilized for electrical drives. Nowadays, in most applications the electrical machine is fed by an inverter. Three types of machines are available for such purposes: the asynchronous induction machine, the permanent magnet excited synchronous machine and the synchronous reluctance machine. Reluctance machines represent an alternative to the other types when utilized in high-performance drives with a wide speed range. Due to the rotor saliency, these machines have an inherent suitability for a position-sensorless control. The parameters of a 5 kW machine with a maximum speed of 8000 rpm are evaluated by means of nonlinear finite element analyses. With regard to an application in a high-performance drive with a wide field-weakening range and a position-sensorless control scheme, the characteristics are calculated for the conventional reluctance machine as well as the reluctance machine with additional permanent magnets in the rotor. The comparison of the characteristics of the conventional reluctance machine and the permanent magnet assisted reluctance machine clearly shows the improved performance in terms of electromagnetic torque and power factor due to the interior permanent magnets. Thereby, the suitability for the application in position-sensorless drives due to the high effective saliency is preserved.     

Regelung von Tangential- und Radialkräften in bürstenlosen permanentmagneterregten Motoren

Electrical drives for pumps or blowers, which are exposed to abrasive media or which must operate absolutely free of wear and tear are hardly feasible with conventional bearings. As a possible alternative to conventional sliding or roller bearings a bearingless motor may be used. In this paper a control scheme for bearingless motors with permanent magnet excitation is presented. This scheme can help reduce the complexity of the power amplifier substantially. Especially, when the motor is operated in conjunction with a voltage source inverter it is possible to observe the state variables by means of a mathematical model, thus measurement of the phase currents is no longer necessary. Control of the radial rotor position, however, requires a nonlinear controller design.     

Experimental evaluation of the total shielding current in a bulkhigh-Tc superconductor [YBaCuO]

Total shielding currents of a melt processed bulk high-Tc superconductor (HTS) are evaluated from the measured voltage of a Rogowski coil when a permanent magnet is moved towards the HTS. The total shielding current and the levitation force between the magnet and the HTS show rapid growth and decay depending on the speed of the magnet. The dynamic levitation force and the magnetic relaxation are discussed from the experimental results     

Modeling and control of a new horizontal-shaft hybrid-type magneticbearing

This paper reports on the development of a new horizontal-shaft hybrid-type magnetic bearing system. The bearing system will be used for a horizontal-shaft machine. The rotor is levitated due to the repulsive force between a stator and a rotor permanent magnet (PM). A lower cost and higher radial stiffness have been achieved by using a strontium-ferrite magnet on the rotor and an Nd-Fe-B PM above and below the rotor magnet. A finite-element analysis was performed to calculate the levitation force and radial stiffness. An upper stator magnet subtending an angle of 45° provides the best compromise between a large levitation force and radial stiffness. A model for the horizontal-shaft hybrid magnetic bearing system has been developed and includes the effect of the rotor dynamics and the electromagnetic forces. An integral servocontroller was designed to stabilize the axial position. The controller has been implemented in a digital signal processor. Experimental results performed on a prototype system are in agreement with the theoretical results     

Magnetically levitated micro PM motors by two types of activemagnetic bearings

This paper describes magnetically levitated micro permanent magnet (PM) motors by two types of active magnetic bearings. The micro PM motors consist of a cylindrical rotor (φ2.0 mm×10 mm), a pair of electromagnets, a pair of photodiodes, and an analog PD controller. The motors are characterized by the small rotor levitated without any mechanical contacts and one-axis controlled active magnetic bearing. Horseshoe-shaped and cylindrical electromagnets are applied to the active magnetic bearing. The rotor successfully rotates, levitating in the center of the electromagnets. In this paper, dynamic characteristics of the two types of micro PM motors, such as relationships between rotation speed and driving current, rotation speed and time, and acceleration and driving current, are discussed. As a result, it is found that the magnetically levitated micro PM motors by two types of active magnetic bearings are very different from each other and very promising     

Permanent magnet excited brushed DC motors

Brushed DC motors excited with permanent magnet material can be found in a wide range of applications. The largest market segment for this type of motor and their predominant use is found in the low-power range. New developments in the area of high-energy permanent magnet material offer the opportunity of miniaturization and promise a cost-effective design. Starting with a brief summary on the permanent magnet material, special design considerations and typical constructions followed by motor applications of radial and axial field configurations are discussed. Particular attention must be paid to the construction of the permanent magnet excited brushed DC motor with respect to the manufacturing costs. Common winding arrangements and cost-effective lamination constructions are presented to illustrate different manufacturing techniques and possibilities     

A new MAGLEV system for magnetically levitated carrier system

A power-saving electromagnetic suspension system has been developed in which electromagnets with permanent magnets are used to suspend the vehicle. The electromagnets are controlled to maintain air gap length so that the attractive force by the permanent magnet always balances the total weight of the vehicle and its loads, based on modern control theory. This technology realizes a significantly power-saving system in which the electromagnetic coil current required to keep a vehicle levitating was extremely small, ideally zero. The 8-kg weight test vehicle with 4-kg load could be levitated continuously over 8 h, without recharging the on-board 1300-mAh batteries. This technology realized a completely contact-free material transportation system when combined with a contact-free driving system using linear motors. The attractive force characteristics of a permanent magnet with control electromagnets and the newly developed electromagnet control system that can eliminate power collecting devices from the electromagnetic suspension system are described     

Scanning our past from London. Using yesterday's engineeringtomorrow: Eric Laithwaite

Old ideas can sometimes gain a new lease on life. Ideas that have once been tried and then discarded as impractical can be re-introduced when changed circumstances or new materials make it possible to do things that were impossible in earlier years. A good example of this re-application of earlier technology is the linear motor and the work of Eric Laithwaite (1921-1997), who applied these devices to modern transportation systems, including a possible future application in space. Originally, the idea was clearly described in patents from the 1840s, and at least one piece of a linear motor made by Charles Wheatstone survives from that time. Such machines could not have been exploited in the mid-19th Century. The necessary current was not available in the days when electrical engineers were dependent for their supplies on batteries or massive permanent magnet generators. Towards the end of the century, practical generators with wound fields became available, and these were capable of producing large currents, but at the same time, it was also found that the same machines could operate in reverse, as motors, and so it was not necessary to design electric motors as separate machines     

Dynamic and Vibration Analysis of a Multimotor DC Drive System With Elastic Shafts Driving a Tissue Paper Machine

In this paper, the influence of the stiffness and damping of real elastic shafts on the behavior of a multidrive system driving a tissue paper machine is investigated. The drive system consists of four DC motors, where two of them drive the Yankee drying cylinder and the other two drive the presses section. Six-pulse thyristor bridge power converters that are connected to the same power transformer supply the motors. The inertias of the motors and the driven machines, in conjunction with the shaft stiffness, form mechanical resonators. Thus, resonance phenomena may occur, which may lead to undesirable results. This particular case results to two three-mass and one five-mass systems. This paper presents an analysis of the resonance frequencies of two sections of the machine during startup and machine production, considering the shaft stiffness (shaft diameter, length, and thickness). The elastic shafts eliminate the ripple of the motor electromagnetic torque, which is transferred to the driven machine. The behavior of elastic shafts with different stiffness in the transmission system is studied. Moreover, the steady state and dynamic behavior of the system considering the influence of the elastic shafts and vibration analysis were investigated using simulation. A model algorithm for system simulation was developed using the MATLAB/SIMULINK software. Characteristic simulation results are presented and are expressed in terms of speed and torque response. Considering the resonance frequency analysis and simulation results, mechanical design guidelines can be given for the most significant drive components in order to avoid torsional oscillation resonance phenomena and minimize torsional oscillations of the drive system.     

Brushless permanent magnet (BPM) motor drive system usingload-commutated inverter

The goal of this work is to develop a brushless permanent magnet (BPM) motor drive system with low total system cost, high reliability and adequate performance for high-volume production and application to commercial appliances. The power converter used is a low-cost thyristor-based load-commutated inverter (LCI). Although LCIs have been used to supply sinusoidally excited permanent magnet motors, their application to BPM motors is a key contribution of this work. A detailed digital computer model capable of predicting the steady state as well as the transient performance of a BPM motor driven by an LCI has been developed. The utility-side phase-controlled rectifier, as well as the motor-side inverter-including the DC-link inductor, are modeled. A load-commutated inverter specifically designed to supply the BPM motor has been fabricated in the laboratory. The developed control strategy has been implemented on an INTEL 80C196KD microcontroller board. Simulation and experimental results to support the use of an LCI to drive a BPM motor are included in the paper     

基于FOC的PMSM速度控制系统的研究

根据磁场定向控制理论以及永磁同步电动机调速控制系统的控制方案建立仿真模型,并对永磁同步电动机的调速过程进行仿真.仿真结果较好地反映了永磁同步电动机的调速运行过程,对进一步开发永磁同步电动机速度控制系统具有重要意义.     

Modeling, identification, and compensation of pulsating torque inpermanent magnet AC motors

Permanent magnet AC motors generate parasitic torque pulsations, owing to several electromagnetic phenomena, such as imperfections in the motor and in the associated power inverter. Excitation of the mechanical resonances on the load side is generally the worst consequence of such disturbances; speed oscillations arise which may dramatically limit the performance in high-precision applications. A compact model of the pulsating torque in sinusoidal permanent magnet motors is presented in this paper, based on a combination of theoretical analysis and experimental identification. Online identification algorithms and a compensation scheme are also outlined. The control scheme autonomously identifies the parameters of the disturbance model through simple closed-loop motion experiments. The compensation is then applied as a modification of the output of the position controller. Experiments carried out on an industrial robot demonstrate the effectiveness of the control scheme in suppressing oscillations, both on the motor and on the load sides     

New design of hybrid-type self-bearing motor for small, high-speed spindle

A new structure of hybrid (HB)-type self-bearing motor is proposed for miniature spindle motors. The proposed design combines the HB-type self-bearing motor and HB active magnetic bearing in the common stator and rotor pair to generate large radial forces. First, the principle and theoretical background are introduced. Then, the air gap flux is analyzed by the finite element method, and radial forces for the proposed and standard-type HB self-bearing motors are compared. Finally, experiments are conducted to confirm the performance of the proposed motor. The motor can run at relatively high rotating speed with relatively high torque compared with its small size. The levitation is very stable and the motor indicates good performance for practical application.     

Novel permanent magnet motor drives for electric vehicles

Novel permanent magnet (PM) motor drives have been successfully developed to fulfil the special requirements for electric vehicles such as high power density, high efficiency, high starting torque, and high cruising speed. These PM motors are all brushless and consist of various types, namely rectangular-fed, sinusoidal-fed, surface-magnet, buried-magnet, and hybrid. The advent of novel motor configurations lies on the unique electromagnetic topology, including the concept of multipole magnetic circuit and full slot-pitch coil span arrangements, leading to a reduction in both magnetic yoke and copper, decoupling of each phase flux path, and hence an increase in both power density and efficiency. Moreover, with the use of fractional number of slots per pole per phase, the cogging torque can be eliminated. On the other hand, by employing the claw-type rotor structure and fixing an additional field winding as the inner stator, these PM hybrid motors can further provide excellent controllability and improve efficiency map. In the PM motors, by purposely making use of the transformer EMF to prevent the current regulator from saturation, a novel control approach is developed to allow for attaining high-speed constant-power operation which is particularly essential for electric vehicles during cruising. Their design philosophy, control strategy, theoretical analysis, computer simulation, experimental tests and application to electric vehicles are described