摘要:

The study includes the analysis and simulation of inverter-fed squirrel-cage induction-machine drives. The particular drive used for experimental validation was a 120° square-wave inverter feeding atubular axle induction motor developed for rail traction by the British Railways Board. The system and its operation in self-excited braking are described. An original analogue model of the inverter is developed that issuitable for the simulation of commonly used types of inverters. Results from the real system and from the simulation compare well for both transient and steady-state operation.

DOI:10.1049/ij-epa.1978.0018

出版商:IEE    

年代:1978

数据来源: IET

摘要:

The device is an extension of the principle of the linear helical reluctance motor but in which arotating magnetic field is achieved by rotating mechanically a set of permanent magnets. Precise correlation between rectilinear displacement and angular rotation is given by the helical saliency of the rotating armature. Preliminary results from a proto type version of the device are described.

DOI:10.1049/ij-epa.1978.0019

出版商:IEE    

年代:1978

数据来源: IET

摘要:

In air-cored chokes the power dissipation due to sinusoidal current may be minimised by suitable choice of conductor size. The optimum conditions may be used with nonsinusoidal current without harmonicanalysis if the current waveform is known.

DOI:10.1049/ij-epa.1978.0020

出版商:IEE    

年代:1978

数据来源: IET

摘要:

The paper describes the operation of a slip-ring induction motor with a thyristor-rotor-current chopper in an asymmetrical mode. A composite torque/speed characteristic is obtained, partly from the conventional balanced characteristic of symmetrical operation, and partly from the single-phase rotor characteristic. A symmetrical component approach to the system solution is given and the system is shown to give shunt-type torque/speed characteristics as a motor or a generator in the speed range from 50% to 75% of synchronous speed. System efficiencies are comparable with those obtained in symmetrical chopper operation above 75% of synchronous speed. An appropriate selection of symmetrical and asymmetrical chopper operation is shown to effectively double the speed range of the symmetrical chopper system. Closed-loop speed control of the variable mark/space ratio chopper can provide steep shunt-type, torque/speed characteristics over a speed range from 50% of synchronous speed to normal full speed with a simple, cheap, 2-thyristor current chopper.

DOI:10.1049/ij-epa.1978.0023

出版商:IEE    

年代:1978

数据来源: IET

摘要:

A brief description is given of existing methods of calculation of the asynchronous starting performance of solid salient-pole synchronous motors. These methods evaluate an equivalent impedance to represent the eddy-current loss in the solid-iron pole. This impedance is a variable, dependant on the rotor slip frequency and flux. The power factor of this equivalent impedance is a fixed quantity. The lumped-circuit parameter is then used in an equivalent circuit to calculate the asynchronous values. The harmonic torque and current associated with the Görges effect need to be examined as these can affect the shape of the characteristics close to half speed and can cause a synchronous motor to run in the region of half speed with a heavy current pulsation. A new computational direct-search method is then described and used to evaluatethe average asynchronous values of torque and current for a solid salient-pole synchronous motor. The method allows for the provision of the distributed entry of flux into the saturable solid pole, pole-tip saturation and the evaluation of space-harmonic flux values. The need to make assumptions about eddy current distribution is eliminated by taking a path of integration on the pole surface. The method is completely general and any relative stator and rotor position can be analysed. Comparisons between the results from this new method, existing methods and test results show that the new method gives consistently accurate answers.

DOI:10.1049/ij-epa.1978.0024

出版商:IEE    

年代:1978

数据来源: IET