摘要:

The measurements, on a single pulse function of electromagnetic radiation, of the position of a scatterer with polar co-ordinatesR, φ are interdeterminate in themselves. The positional indeterminacies are related by ΔRΔφ ≃ ½λt, where λtis the wavelength of the source. The relation between the indeterminacies of rangeRand radial velocityVris found to be ΔRΔVr≃ ¼λtC. It is shown that vector position and vector velocity are not measurable simultaneously, and it is suggested that the 3-dimensional measurement problem is basically limited to non-simultaneous measurements which have restrictions in the presence of multiple scatterers. Similarity is noted to the quantum-mechanical problem.

DOI:10.1049/pi-c.1961.0033

出版商:IEE    

年代:1961

数据来源: IET

摘要:

The electric and magnetic circuits of electrical machines are generally so complex that the exact evaluation of such quantities as leakage reactance and a.c. resistance is virtually impossible. With the advent of digital computers it has become feasible to develop numerical methods of predetermining the flux pattern in such cases. In the paper the finite-difference equations for electromagnetic systems are obtained, and the inductance is calculated by integrating the magnetic vector potential over conducting surfaces. The same finite-difference equations are applied to the calculation of a.c. resistance of conductors in slots. The use of the method is illustrated by examples of standard transformers, a tap-changing transformer, calculation of the leakage reactance of the field winding of a salient-pole-alternator and the screening of d.c. poles in a new type of oscillating synchronous linear machine.

DOI:10.1049/pi-c.1961.0034

出版商:IEE    

年代:1961

数据来源: IET

摘要:

The paper considers the distortion introduced by torque saturation in a servo mechanism when responding to a randomly varying input signal, with emphasis on the spectral distribution of this distortion. It is shown that low-frequency errors are produced by the application of an input signal whose spectrum extends beyond the pass band of the system.An approximate expression is derived which enables the magnitude of the low-frequency errors to be evaluated in a simple manner. Experimental results are presented for a particular system.

DOI:10.1049/pi-c.1961.0035

出版商:IEE    

年代:1961

数据来源: IET

摘要:

A class of non-linear error-detector characteristics is considered where, for large magnitudes of error, the error signal decreases with increased error. Sinusoidal and random-input analysis of a closed-loop system containing such a non-linearity is shown to necessitate the calculation of a family of describing-function curves to cover operation with a d.c. input signal to the non-linear error detector. The peculiarities of such a non-linear system are discussed, and a simple method using a non-linear circuit to correct the adverse behaviour is described.

DOI:10.1049/pi-c.1961.0036

出版商:IEE    

年代:1961

数据来源: IET

摘要:

On power lines the currents which flow solely in the phase conductors travel near the velocity of light whereas those which return through the ground and overhead earth wires travel more slowly, the speed depending on the line spacings, conductor sizes and nature of the ground. The full steady-state equations for a 3-phase line are developed and a particular line is examined to show the magnitude of this effect. The effect of transposing a line is also indicated.The steady-state performance of basic distance protection fitted with compensating equipment to allow for the effects of the currents in the sound phases during earth faults is studied, using the line equations. It is shown that large errors of measurement occur under earth-fault conditions on long lines fed from small sources. The performance for faults which do not involve earth is satisfactory.It is shown that non-transposition of a line makes the apparent impedance of a fault on a line depend on the source impedance. This causes further errors in the assessment of the positions of faults of all types.The high transient time-constants on long lines increase the chance of maloperation during the transient period.It is concluded that distance protection may not be satisfactory on very long lines and that a study must be made of the complete power system before a decision can be made about its suitability for any particular application.

DOI:10.1049/pi-c.1961.0037

出版商:IEE    

年代:1961

数据来源: IET