摘要:

A computer-aided steady-state analysis is presented for a saturable reactor assisted soft-switching DC-DC convertor. The convertor achieves efficient soft-switching without limitation for both load current and output voltage. The current and voltage waveforms, and performance characteristics are illustrated and discussed. The analytical results are presented in the form of normalised graphics. The experimental results indicate reasonable agreement with calculations.

DOI:10.1049/ip-b.1992.0033

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The paper presents a technique for calculating the current/time profile for a remote short circuit fault at a DC rapid transit railway substation. The profile is largely determined by steel rail impedance, which is shown to vary with time within the profile. An inverse Fourier transform, employing a novel antialiasing method is applied to obtain the profile from frequency based impedance data. The technique is demonstrated to be accurate to within 10% with a comparison between a calculated profile and practically measured results obtained on a light rail system. The impedance data required in this technique can be obtained by either measurement or calculation and scaling of standard values using the method described in a companion paper.

DOI:10.1049/ip-b.1992.0034

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The paper presents a detailed analysis of appropriate electrical impedance models for steel railway rails suitable for power supply circuit transient calculations. It extends existing models to fully describe the skin effect, so that power circuit transient behaviour can now be taken into account with little error in prediction of response. Practical measurements of rail impedance are compared with calculated values of circuit impedance and demonstrate an accuracy of within 9% for resistance and 18% for inductance. An associated paper shows how this model can be used to predict remote short-circuit-fault substation current profiles.

DOI:10.1049/ip-b.1992.0035

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The distortionless conditions between nonsinusoidal voltages and currents are deduced, and the definitions of distortion current, distortion voltage and distortion power are introduced. The authors discuss some current formulas for nonsinusoidal power.

DOI:10.1049/ip-b.1992.0036

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The paper seeks to illuminate the influence of the choice of the number of pole pairs on the performance of switched reluctance motors. A simple model is analysed to obtain insight into this simple design choice, which has complex nonlinear effects. This understanding is tested against the results of computer modelling.

DOI:10.1049/ip-b.1992.0037

出版商:IEE    

年代:1992

数据来源: IET

摘要:

It is shown that the cogging torque in permanent magnet and brushless DC motors, where the number of magnet poles is close to the number of armature slots, can be reduced considerably by adjusting the width of the poles or the width of the slots. A design method to achieve this goal is presented. The influence of the slot opening on the cogging torque is thoroughly investigated theoretically and experimentally for a prototype.

DOI:10.1049/ip-b.1992.0038

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A pattern recognition approach to analyse transient stability using a higher order model is presented. A six order model based on two axis representation for generators including voltage and governor actions is described. Two pattern vectors based on physical considerations about the system behaviour are derived and several approximations on system trajectory are considered to deduce analytical formulas which can be computed quickly. To alleviate computational time, two discriminant analysis methods allowing reduction of pattern vectors are presented. These results are applied to an eight machine system with a three phase fault. The discriminatory power of the pattern vectors proposed is tested with Bayes classifier and theknearest neighbour rule. A comparison is given.

DOI:10.1049/ip-b.1992.0039

出版商:IEE    

年代:1992

数据来源: IET

摘要:

An analytical study of the hybrid permanent-magnet synchronous/stepping motor is presented in which possibilities for stabilising the machine are examined. It is shown that stability can be achieved by either frequency modulation or amplitude modulation of the supply at the ‘hunting’ frequency of the motor/load combination. The characteristics of the electromagnetic damping-torque coefficient are investigated to determine the constraints involved in the development of satisfactory stabilisation schemes.

DOI:10.1049/ip-b.1992.0040

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Asymmetry of three-phase loads causes deterioration in the power factor and power quality of a circuit. Waveform distortion aggravates these unfavourable effects even more. A method of improving the power factor and the loading symmetry in a three-phase unbalanced circuit under nonsinusoidal conditions is presented. The method discussed is based on the source current orthogonal decomposition into the active, scattered, unbalanced, and reactive components, recently developed for three-phase asymmetrical systems. The paper shows that this current decomposition provides the fundamentals for the design of passive compensators which can effectively reduce the unbalanced and reactive components of the source current under nonsinusoidal conditions.

DOI:10.1049/ip-b.1992.0041

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The paper presents a theoretical performance analysis of several control strategies for synchronous reluctance machines which are being fed from a current controlled inverter. The three main control strategies considered have as their objectives to allow maximum rated torque, maximum rate of change of torque and maximum power factor, respectively, from the machine. These control strategies are investigated to determine their limitations and inter-relationships. A technique for ‘field weakened’ control of the machine is developed. It is shown that the rate of change of torque performance of the control strategies based on constant current angle is poor at lower angular velocities. A control strategy based on having constant current in the most inductive axis of the machine is shown to give better performance under these conditions, and a technique for moving between control strategies is developed.

DOI:10.1049/ip-b.1992.0042

出版商:IEE    

年代:1992

数据来源: IET