摘要:

An attempt is made to obtain an analytical solution for the field distribution inside solid magnetic cores subjected to an alternating magnetic field when the range of operation of the magnetizing force is limited to the first portion (up to the knee) of theB/Hcurve that can be approximated to the formB= μ(H− εH3), ε being small. As a first stage, an analytical method is developed for the solution of the partial differential equation of the form∂2H/∂x2= μ/ρ ∂/∂t(H− εH3)Hbeing a function ofxandt.Based on this method, expressions for the field distribution, eddy-current loss and overall power factor are deduced. Furthermore, the above analysis is modified to take account of the presence of hysteresis. It is claimed that the method gives a clear picture of the saturation phenomenon and offers an explanation for the increases in loss and power factor that accompany saturation. The analysis is applied to the specific case of a mild-steel toroid and verified against the test results.

DOI:10.1049/pi-c.1962.0031

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A graphical solution, which gives the sequence voltages, starting-torque ratio, line current, the voltage across the capacitor and the corresponding values of a dimensionless admittance ratio for a 3-phase induction motor at standstill and connected to a single-phase voltage, is derived. Several optimum conditions, in particular an exact admittance ratio for minimum unbalance, are obtained from the locus diagram. In all cases it is shown that the admittance ratio obtained is independent of the applied voltage and the locus diagram is therefore applicable to machines of any rating.

DOI:10.1049/pi-c.1962.0032

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A method of minimization of Boolean functions is described. Though directly concerned with the evaluation of the minimal sum of products, it can be easily extended to obtain the minimal product of sums. It has been shown that, after the selection of the essential prime implicants, there exists a ‘row-merger’ step or a ‘row-merger’ and ‘row-cancellation’ step which reveals many alternative covers. The method of obtaining the solution for the cyclic prime implicant matrix has been systematized by introducing the ‘irredundantSat-set’ and the ‘perturbation set’ of the prime implicants. The method yields all the minimal sums, however complex the problem may be.

DOI:10.1049/pi-c.1962.0033

出版商:IEE    

年代:1962

数据来源: IET

摘要:

When analysing electrical machines, certain physical concepts are common to all machines whatever the axes of reference, e.g. resistance voltage-drop. These invariant quantities can be expressed mathematically as tensors. The paper investigates the form of the invariant equations of a two-machine system. One basic equation in its general transient form, and the corresponding hunting equation, are used for the two individual machines, and it is shown that the same two equations apply to the connected system.The tensor equations are expanded to give the full matrix equations of the system. The application of the latter has already been published by the authors.

DOI:10.1049/pi-c.1962.0034

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The flow graph, introduced by C. L. Coates, is a structure, allied to the signal flow graph, which allows the solution of a system of linear equations to be found in a way which avoids certain redundancies. It is shown in the paper how the essential advantages of Coates's theory can be incorporated into signal-flow-graph analysis. Where network theory is concerned it seems preferable to retain the signal-flow-graph form, and the reasons for this are discussed. In addition, the precise relations between graph determinants and the determinants of ordinary algebraic theory are examined. The paper concludes with a comparison of the algebra of flow-graph and of signal-flow-graph transformations.

DOI:10.1049/pi-c.1962.0035

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The electric and magnetic field vectors in the air-gap of an induction machine are derived from a scalar potential which satisfies Laplace's equation; the application of boundary conditions at the stator and rotor surfaces then leads to a complete knowledge of the air-gap field and the rotor current in terms of stator current. All the electric and magnetic quantities can be expanded in a series of travelling harmonics, each of which produces its own component of torque and rotorI2Rloss. The pulsating component of torque is the only derived quantity which depends upon interaction between harmonics.The general theory is applied to the polyphase machine, the singlephase machine and the 2-phase servo-motor; in each case the result conforms with accepted theory. The theory could well be applied to machines with unusual stator windings.

DOI:10.1049/pi-c.1962.0036

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Using a slotted line, a method has been developed to measure small and rapid variations, Δε′ and Δε″, in the real and imaginary parts, ε′ and ε″, of the relative permittivity of a dielectric, at frequencies in the range from 250 to 2000 Mc/s. Some measurements made by this method on ferro-electrics during switching are reported and give consistent results.

DOI:10.1049/pi-c.1962.0037

出版商:IEE    

年代:1962

数据来源: IET