DOI:10.1049/pi-2.1950.0001

出版商:IEE    

年代:1950

数据来源: IET

DOI:10.1049/pi-2.1950.0002

出版商:IEE    

年代:1950

数据来源: IET

DOI:10.1049/pi-2.1950.0003

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The regulation characteristics of a transformer can be specified by three complex parameters, commonly the magnetizing admittance, and the primary and secondary impedances. The paper shows that for practical purposes a no-load admittance, a source impedance, and a complex ratio, form a more convenient system of parameters. The relationship between the two systems is set out diagrammatically.The advantages of this approach become pronounced when an exact theory is required. The theory is applied to the interpretation of test results on a transformer supplying a variable-resistance load. It is shown that even when the no-load current is large, the primary and secondary current vectors can be represented as terminating upon a common circular locus.

DOI:10.1049/pi-2.1950.0005

出版商:IEE    

年代:1950

数据来源: IET

摘要:

Established methods for the resolution of an unbalanced system into positive-and negative-sequence components are extended to give information about their relative phase-displacement. The method developed depends on the inherent property of dynamometer instruments that, for given currents in the coils, the deflection is proportional to the cosine of their phase difference.A dynamometer instrument of ordinary design was modified simply for the purpose by separating the coils and connecting the ends to external terminals, two similar resistance-capacitance networks being added.If it is assumed that the zero-sequence component is absent, or has been eliminated, three readingsr1,r2andr12and one unrecorded test of a qualitative nature are sufficient for a complete analysis. The test serves to determine the sign of the phase angle, the sequence componentsr1andr2are given directly, and the expression cos π=r122/(r1r2) enables the phase angle to be found. The only calculation is very simple, and the solution can be obtained quickly from nomogram.

DOI:10.1049/pi-2.1950.0014

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The paper describes apparatus suitable for measuring the frequency response of servo mechanisms and similar devices. The voltage and waveform of the supply are substantially independent of the frequency used, and there are two outputs of known and variable phase relation. One of the outputs is used to oscillate the servo mechanism, while the other is used to follow the phase shift through the servo transmission, an oscillograph being used as a phase null indicator. The frequencyconvertor of a Schrage motor is used to provide the supply, the phase calibration being obtained either on the brush gear, or on a phase shifter supplied at 50c/s and operating through an induction-type frequency changer. The rotor is independently driven by a d. c. motor at a speed depending upon the frequency required.Two impedance determinations, covering a frequency range 0.5–150 c/s, illustrate the types of measurement possible. A test on field coil at a constant potential of 20 volts, is an example at low power test on the free-to-run armature of a separately-excited motor, at constant current of 30 amp, is an example at high power. The effects of armature reaction in the frequency convertor are briefly discussed, and tests of the phase calibration of the Schrage machine are described.

DOI:10.1049/pi-2.1950.0016

出版商:IEE    

年代:1950

数据来源: IET