摘要:

The Channel Tunnel 25 kV railway system will be supplied from the UK and French 400/225/132 kV grid systems. The paper describes the preliminary unbalance and harmonic studies carried out for the tunnel traction system. The studies explore the interaction between the tunnel traction loads and the grid supply systems. The studies were carried out for the most severe loading conditions, determined from previous studies of rail traffic patterns, imposed on the grid systems in their electrically weakest state. Specific harmonic and unbalance limits were used against which the results of the studies were assessed. These studies form the first stage in the design process that will lead to the definitive design of the Channel Tunnel traction systems.

DOI:10.1049/ip-b.1991.0006

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper presents an investigation into the leakage fields and eddy current losses in the windings of inductors and coupled inductors used in high frequency applications. It shows that the eddy current losses in the windings can be reduced significantly by the use of distributed airgaps, and that under these conditions the leakage fields are predominantly one dimensional so that the losses can be predicted analytically. Mutual losses produced by one winding in another are examined. It is shown how ferrite core designs can be modified to ameliorate further AC winding losses. These techniques taken together show that winding eddy current losses in inductors and coupled inductors can be reduced almost by an order of magnitude. Thus inductor efficiency can be improved, and the way becomes open for the design of inductors for higher frequency circuits.

DOI:10.1049/ip-b.1991.0007

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper presents a consistent electromagnetic theory of a multilayer rotor induction motor with distributed parameters. Equations describing the two-dimensional field distribution in the rotor have been used to obtain recurrence relations for the resultant rotor impedance. These relations include the higher space harmonics produced by the stator MMF curve. The classical T configuration equivalent circuit has been extended and adjusted to model a multilayer rotor. Positive- and negative-sequence currents have been taken into account and impedances for forward- and backward-travelling field have been found.The method of the performance calculation for a multilayer rotor induction motor, including current assymetry and higher space harmonics, has been worked out. The approach presented may be helpful in the analysis and synthesis of induction machinery with specially constructed rotors (secondaries). The existing theory has been developed and generalised.

DOI:10.1049/ip-b.1991.0008

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A technique is presented for estimating the stator flux magnitude in an induction motor from the DC link current. The signal produced has a wide bandwidth and is used in a feedback control system that maintains the stator flux magnitude at any desired value. The steady-state performance of an induction motor controlled in this way is modelled and compared with practical results. No speed, flux, voltage or current transducers are mounted on the motor. The effect of temperature variation on winding resistance is compensated for by using saturation-induced harmonics to indicate errors between the parameters from the controller model and the real motor.

DOI:10.1049/ip-b.1991.0009

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The problem of 3-dimensional steady-state heat flow in the stator of an induction motor is solved by use of a finite element formulation and arch-shaped elements. The shape functions and exact solution matrices are derived algebraically for utmost economy in computation. The temperature distribution has been determined considering convection from the surface and the two ends. First, a simple cylinder has been taken as an example. Then, the temperature at different location in the stator of the induction motor has been computed.

DOI:10.1049/ip-b.1991.0010

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The brushless exciter is now widely used in alternator excitation systems as it offers the advantage of reduced maintenance. An accurate modelling of the exciter-alternator set is important for design and operation engineers. In the paper, an accurate detailed model of the set is presented. The exciter is modelled as a synchronous machine in the direct phase reference frame, to comply with the nature of the rectifier circuit. Kron's tensor method for analysis of electrical circuits is utilised, and a variable connection matrix is developed to suit the variable topology of the exciter circuit. A complete mathematical model that covers all the modes of operation of the rotating bridge rectifier circuit is developed. Short circuit transient results are computed and compared with test results.

DOI:10.1049/ip-b.1991.0011

出版商:IEE    

年代:1991

数据来源: IET

摘要:

A new soft-switching converter technique is introduced which employs small saturable reactors and phase-shift modulation. This considerably reduces switching losses with no substantial increase in conduction losses. The proposed soft-switching concept and its modifications to full-bridge DC-DC power convertors are shown and discussed. These convertors can be realised by only a few additional small magnetic components with conventional full-bridge PWM convertors. The steady-state characteristics are verified analytically and experimentally through 350 W, 500 kHz breadbords.

DOI:10.1049/ip-b.1991.0012

出版商:IEE    

年代:1991

数据来源: IET