摘要:

An analysis of a class D voltage-switching tuned power amplifier is given, along with experimental results. Analytical equations are derived for performance parameters at any operating frequency normalised with respect to the resonant frequency and at any load resistance normalised with respect to the characteristic impedance of the resonant circuit. The analysis is carried out under the high loaded quality factor assumption, using Fourier series techniques. The behaviour of power MOSFETs in class D circuits for both capacitive and inductive loads is discussed in detail. It is shown that the operation above the resonant frequency (an inductive load) is preferred. The theoretical results were in good agreement with measured circuit performance parameters. The equations provide easy-to-use design tools, which can find a broad application, e.g. in designing DC/DC resonant converters and DC/AC inverters.

DOI:10.1049/ip-b.1991.0035

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A numerical computation of squirrel cage induction machine parameters is presented using the finite element method (FEM). The effects of main field saturation are studied and the different parameters can be calculated for any magnetising current value. To take into account magnetic state variations, a ‘dynamic’ mutual inductance is introduced into the saturated machine model. All these parameter values are used in the field-oriented control system realisation, and experimental results are described for constant and weakened flux operating points. Special attention is given to the adaptation of the control law during flux-weakening, to take into account desaturation effect. The results obtained are quite satisfactory.

DOI:10.1049/ip-b.1991.0036

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Short circuits applied close to substations cause large transient peak fault currents, but remote faults are difficult to detect because the fault current may be less than a normal train load. It is important to be able to predict the form of both closeup and remote fault currents for design of new protection systems and to assess the suitability of particular protection arrangements for specific railways sites. The model of the substation rectifier is an essential part of any means of predicting the current profiles. A detailed rectifier model based on a piecewise linear digital simulation, particularly suitable for prediction of fault current profiles owing to closeup faults is presented. The accuracy is demonstrated by comparison with a case study of a practically measured fault current profile. It is shown that commonly used models based on simpler equivalent circuits can not match the accuracy of the detailed model. It is also shown that a simple DC power source model of a rectifier is appropriate for remote fault calculations because the profile is not significantly affected by the switching action of the rectifier. The validity of the simpler model is demonstrated by comparing the simple model with the more detailed one.

DOI:10.1049/ip-b.1991.0037

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Theoretical models for rail internal self-inductance and resistance are proposed which include material saturation and hysteresis. Model data are obtained using experimentally derived ferromagnetic materialB-Hloops. Analytical methods for deriving the impedance variations with current and frequency for large-signal AC and incremental AC superimposed on DC excitation are in agreement with experimental measurements.

DOI:10.1049/ip-b.1991.0038

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper describes a static test which, in conjunction with a no-load test, can be used to determine the parameters needed to apply the two-axis machine analysis to modern rare-earth permanent magnet synchronous motors. An iterative solution of the two-axis theory is presented which, together with the static test, avoids the use of the load angle. The solution includes the effect of core (iron) loss and allows for the estimation of current, power factor and efficiency for a motor running normally from inputs of terminal voltage and torque alone. The parameter values and machine performance predicted by the new methods are confirmed against test data obtained from a samarium-cobalt synchronous motor which has an asymmetrical buried magnet rotor. For this configuration, it is observed that saturation can cause significant variation in the permanent magnet excitation and the direct-axis synchronous reactance as well as the quadratureaxis synchronous reactance. When the variation of each of these parameters is included in the analysis, it is found that the two-axis theory gives a good representation of the motor performance in both the preferred and nonpreferred directions of rotation at a variety of voltages, frequencies and loads.

DOI:10.1049/ip-b.1991.0039

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper examines the virtues of representing the magnetising curves of a switched reluctance motor by customised cubic splines and storing its coefficients in a new data base. It is shown that cubic splines are capable of handling the highly nonlinear characteristics. Furthermore they are found to be well suited for computer efficient generation of the flux linkage/current, torque/angle and current/flux linkage functions as required for drive simulation purposes. A case study demonstrating the use of the new data base as well as its compilation is discussed.

DOI:10.1049/ip-b.1991.0040

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper presents single-phase rectifiers that employ capacitive and inductive energy storage/transfer mechanisms. These are derived from the Cuk convertor and single-ended primary inductor convertors, so that the step-up and step-down characteristics of the output voltage can be easily obtained. The supply current can be sinusoidally waveshaped with a near-unity power factor by means of current reference hysteresis control. To predict their steady-state and transient characteristics successfully the approximate state-space averaging method is introduced with a digital PID controller. The experimental and predicted results confirm the usefulness of the rectifiers prsented.

DOI:10.1049/ip-b.1991.0041

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Parameter variation in the load of a servoposition control drive requires a robust controller. The sliding mode control, which constrains the system motion to a state trajectory, provides for greater robustness than classical control schemes. The design and implementation of a brushless DC servomotor drive using sliding mode position control is described. The design procedure is outlined, and the features of practical sampling rate and supply source limitation are incorporated. The implementation of the system, based on a Motorola 68000 processor, is described, and both simulated and practical responses are presented and evaluated.

DOI:10.1049/ip-b.1991.0042

出版商:IEE    

年代:1991

数据来源: IET