摘要:

A method is described for predicting reliably the pull-out torque characteristics of hybrid stepping motors which are energised from current-regulating drive circuits. The basis of the approach is the representation of the several modes of operation which can occur as a result of the active nature of the drive circuit. Comparisons of experimental and predicted pull-out torque curves are presented.

DOI:10.1049/ip-b.1986.0045

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The paper describes the use of a 2-dimensional finite-element field analysis (FEA) to obtainNφ/i/ rotor position characteristics of a doubly salient switched reluctance motor. The stator and rotor have even but unequal numbers of poles. Unlike the single tooth per pole construction of the most common doubly salient pole motors, the motor considered for analysis has two teeth per stator pole. The increase in torque developed due to the multitooth stator pole configuration has been reported by Finchet al.in May 1984. An accurate knowledge of flux pattern inside the motor is essential to a machine designer for performance prediction. The complex configuration and material nonlinearities of the motor makes analytical methods of magnetic field analysis difficult. The numerical method (FEA) used gives a better understanding of the flux distribution inside the motor. The terminal inductance per phase, the flux linkage of each stator pole winding, and the components of the leakage inductances are determined for different rotor positions and excitation currents. The average torque developed by the motor is also determined under current forced conditions.

DOI:10.1049/ip-b.1986.0046

出版商:IEE    

年代:1986

数据来源: IET

摘要:

Thyristor forced commutated AC/DC convertors are useful for improving the power factor and waveform of AC-side line current. These are controlled through pulse-width modulation schemes for best performance. However, the 3-phase versions impose restrictions on the PWM strategies that can be implemented for excellent harmonic rejection. This paper presents new PWM control strategies for the 3-phase converters and compares them along with the conventional 4-pulse PWM strategy for harmonic elimination. Finally, two new PWM strategies are shown to be the best, for which oscillograms are presented from actual implementation.

DOI:10.1049/ip-b.1986.0047

出版商:IEE    

年代:1986

数据来源: IET

摘要:

TheT-Ω method is presented in a general format, along with a discussion of implications of various assumptions employed here to date. A general methodology for using theT-Ω method is laid out for use using the boundary integral technique. The method is applied and tested on the unbounded wedge problem. Asymptotic limits and empirical results show the technique to be extremely accurate.

DOI:10.1049/ip-b.1986.0048

出版商:IEE    

年代:1986

数据来源: IET

摘要:

Some fundamental considerations regarding power electronics and machine electronics are discussed. The historical development of ideas in this field is examined, the applications in the field of electric traction for rail vehicles are summarised and possible future developments are outlined. A systematic approach to power electronics, based upon the control of energy flow in switching convertors, is presented. This approach takes into consideration the different possible switching functions, the modulation functions, the realisation of these switching and modulation functions, the realisation of these switching and modulation functions by practical power semiconductor switches and the different classes of forced turn-off and commutation in power electronic circuits. Subsequently the concepts of topology and structure are defined, leading to different generic topologies for singular convertors. The structure of the five different families of composite convertors are examined, and practical examples are given.The systematic approach to machine electronics presented in the paper is based on a power flow model, using the unifying concept of rotating field theory. In combination with previously defined systematics for power electronics, this enables a systematic approach to the different classes of variable speed drives, based on power flow considerations.The historical developments of some power electronic and machine electronic ideas are traced, starting at the beginning of this century. Since the introduction of power semiconductor switches, applications of the older ideas have increased exponentially in all fields, making it impossible to cover all of them. As a consequence the development of power electronics and control of machines by electronic convertors in the field of electric traction is discussed in some detail, because this represents a record of important engineering achievements in this field.In conclusion, the present state and future trends of power and machine electronics are examined. This evaluation covers the development in the field of switching devices regarding the improvement of interfacing between signal and power electronics, the decrease of switching transition times, the reduction of device losses during conduction, and device developments for decreasing energy storage devices in convertors.The development of power electronic convertors for the reduction of the number of components in the topology and the development of convertors with a high frequency link are then covered, related to the expected development of switching devices.New directions of development regarding the electronic conditioning of the electromechanical energy conversion process concerning the elimination of undesirable effects and losses are important. The implementation of these trends by utilising the improved switching characteristics of power electronic switches and the information processing capability of microprocessors is discussed. This is then extended toward control aspects, where both these characteristics enable solutions not possible hitherto. Field control of AC machines imparts control characteristics equal to, or better than, those obtainable with DC machines to the systems, while the processing capability of microprocessors allows the configuration of adaptive machine electronic systems. Finally attention is given to the interfacing of power electronic and machine electronic systems to the power supply network. If the exponential growth of the installed capacity of equipment in the future is to be handled, active compensation of the distorted currents drawn from the supply by this equipment will have to be considered seriously.

DOI:10.1049/ip-b.1986.0052

出版商:IEE    

年代:1986

数据来源: IET