摘要:

The New Zealand power system, with a number of large rectifier loads and extensive use of audiofrequency power system signalling (ripple control) for load management, presents particular problems to the designers of harmonic-control measures. The approach adopted in the Limitation of Harmonic Levels Notice differs from that adopted in other standards and guidelines in a number of areas, in particular in its adoption of individual current and voltage limits for the transmission system, the use of psophometrically weighted limits for both current and voltage, the provision of a detailed measurement schedule, and the approach to the equitable sharing of available harmonic capacity. In parallel with the standard, a specially designed monitoring system has been developed to gather information on system harmonic behaviour, and to present this information to a user. A primary role of this equipment will be in the monitoring of power system harmonic conditions, to assess the influence of the legislation in controlling harmonic levels.

DOI:10.1049/ip-b.1985.0026

出版商:IEE    

年代:1985

数据来源: IET

摘要:

We present an analysis of the single-sided linear induction motor with a solid-steel reaction plate. By solving for the two-dimensional field distribution in the airgap and in the secondary, the mutual reactance and secondary impedance are determined. The saturable characteristics of the rail steel, together with the hysteresis, the skin effect, the reaction of eddy currents, and both transverse edge and longitudinal end effects are included. Computations for motoring and for plugging operation under constant-current conditions are compared with experimental results from a large-scale test linear machine, and good agreement is obtained. The analysis, which can also be used for constant-voltage excitation, is valid over a wide range of operating conditions, and is useful for design studies.

DOI:10.1049/ip-b.1985.0027

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A synchronous machine can be constructed with two armatures and one field. If the armatures contrarotate, the armature-reaction flux in the quadrature axis, ideally, is eliminated. The machine therefore operates with a high saliency ratio. The voltage regulation for a unity power-factor load is then only affected by winding resistance and leakage reactance. This unique feature allows the machine to have a peak power capability several times that of conventional machines of the same size. Two contrarotating machines have been designed and tested. One of the arrangements has steady-state behaviour approaching the expected ideal behaviour. The test machine built has three rotatable machine elements which allows the examination of a number of operating modes.

DOI:10.1049/ip-b.1985.0028

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Different aspects of the design of power electronic inverters for low mass welding applications are described. High frequency (15 kHz) is used at power levels up to 10 kW, and emphasis is placed on the minimisation of losses in the ferrite-core transformer and power switches to obtain an efficient and compact system. Attention is given to a very simple low-loss turn-off snubber ideally suited for the application. Two welding systems which were developed and tested are described. These were a 220 V single-phase and a 380 V 3-phase unit. Design considerations and practical results are also presented. It is concluded that such inverters have great potential for application in this field.

DOI:10.1049/ip-b.1985.0029

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The naturally commutated, convertor-fed synchronous machine is being used for drives of very high rating. At standstill and at very low speed, commutation is achieved by pulsing the current in the DC link between the supply and the machine convertors, and this gives rise to significant low-frequency disturbances to the supply system. The paper describes an alternative method, using a discontinuous current mode of operation, which gives smoother operation and less disturbance to the system. An analysis is given which shows that the method can give an average torque as high as 1.0 per unit, and permits the rapid assessment of the potential of the method for a particular application.

DOI:10.1049/ip-b.1985.0030

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Most of the existing papers have dealt with the torque pulsation of an inverter-fed AC motor caused by the behaviour of the inverter. In industrial applications the DC source is achieved by rectifying the AC supply. Therefore the behaviour of this rectifier also influences the torque pulsation. This paper describes analytically the influences of not only the behaviour of the inverter but also the behaviour of the rectifier on the motor torque. The torque pulsation is estimated by using three estimation methods. The selection of filter constants is also discussed.

DOI:10.1049/ip-b.1985.0031

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A novel method to enhance the withstand voltage of a composite solid dielectric with imbedded conducting strips is proposed and the resulting electric-field patterns are deduced. The direction of the electric field inside the dielectric is changed to favour a higher withstand voltage in a given direction by using conducting strips located between alternate layers of the solid dielectric. The strips cover only a portion of the insulating layer. A new method is used for simultaneous calculations of (i) the electric field, throughout the region of the composite insulator, and (ii) the bound charge distributions on the conducting strips. The method is based on the nodal analysis. It has been found that the direction of the electric field can be changed to be away from the electrodes, thus leading to an enhancement of the withstand voltage of the composite insulation.

DOI:10.1049/ip-b.1985.0032

出版商:IEE    

年代:1985

数据来源: IET