摘要:

The paper establishes a simplified theoretical model for variable-reluctance stepping motor systems, based on linearisation of the motor's dynamic torque-producing characteristics about an arbitrary working point. It is shown that, by representing the torque as contours in the speed/switching angle plane, unambiguous stability limits for open and closed-loop operation are clearly defined. A companion Paper [12] shows how the theoretical model provides valuable information about the mid-range instability of a stepping motor system, and provides experimental support for the model.

DOI:10.1049/ip-b.1989.0001

出版商:IEE    

年代:1989

数据来源: IET

摘要:

A design method for L- and T- connected tapped-winding capacitor motor is presented. This method is fundamentally based on the balanced conditions at the full load for high speed connection. At first, performance equations for a tapped-winding capacitor motor are derived by the method of the two-phase symmetrical component. Characteristics of the motor, obtained by the suggested design method, are discussed with regard to both its high and low speed operation. Based on the analytical results, a design procedure for a tapped-winding capacitor motor is suggested. By this procedure, auxiliary winding, extra winding, and the capacity of the capacitor for the given main winding, are easily determined. An example of design for a L-connected tapped-winding capacitor motor is described.

DOI:10.1049/ip-b.1989.0002

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper introduces an unusual form of DC-to-AC convertor using an unregulated inverter, which is transformer coupled to a high frequency cycloconvertor. It gives a brief description of a prototype system and presents some practical waveforms. The main content of the paper is devoted to the development of a modulation law for the square wave cycloconvertor, which is done by comparison with conventional cycloconvertor techniques, and the analysis of the harmonic content of the resulting output waveforms. Comparison is made between the spectra produced by the cycloconvertors and a conventional inverter with sinusoidal pulsewidth modulation. The effects of transformer leakage inductance on the thyristor commutation process is discussed, and the modification made to the output waveform by overlap is identified and analysed; it is found to be small with low-leakage bifilar wound transformers. The effect of source frequency on the transformer leakage inductance is estimated, and it is shown that higher frequency systems are feasible without overlap causing any undue problems.

DOI:10.1049/ip-b.1989.0003

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Certain ferrites, referred to as temperature-sensitive magnetic semiconductors (TMS), exhibit marked temperature dependence in both magnetic and electrical fields. The temperature dependence of TMS resistance is similar to a semiconductor thermistor at low voltages. At higher voltages, three states are observed in the symmetric bidirectional characteristics; these are a cut-off state, a negative resistance state, and an ‘on’ state. Therefore a TMS can be regarded as a multifunction magnetic semiconductor, which has the effect of adding a thermistor and a bidirectional switching device to the temperature-sensitive magnetic core. Application of a TMS switching device for overheating and overvoltage protectors is also discussed.

DOI:10.1049/ip-b.1989.0004

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper reviews the disturbance mechanisms which can exist between chopper-controlled DC traction equipment and low-frequency track circuits which commonly operate at 50 or 60 Hz. It is shown that disturbance exists due to the various modes of chopper circuit operation, as well as to small mains-frequency AC voltage ripple sources which exist in the traction supply. Models are presented which define the sensitivity of single-rail and double-rail track circuits for these conditions. The paper also presents an approximate model for determining the low-frequency input impedance of chopper equipment, for use in disturbance calculations. The developed model is shown to be applicable to single-phase and multi-phase choppers, as well as to chopper circuits which use current-sharing reactors. The accuracy of the developed model is shown by comparison with practically measured values of input impedance using a low-power DC chopper.

DOI:10.1049/ip-b.1989.0005

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper sets out to state clearly the influence of saturation on torque production and energy flow in a doubly salient machine. A comparison is made between the performances of a series of switched reluctance motors, which are identical in all respects except for the iron used. The differences include the use of ideal non-saturating iron; the introduction of saturating material in the pole faces; the use of real iron throughout; and the introduction of a magnetic constriction in the pole faces of a real machine. General conclusions are drawn concerning specific output and volt-ampere demand.

DOI:10.1049/ip-b.1989.0006

出版商:IEE    

年代:1989

数据来源: IET