Electrical impedance

About: Electrical impedance is a research topic. Over the lifetime, 36015 publications have been published within this topic receiving 371891 citations. The topic is also known as: electrical impedance & complex impedance.

Synchronization of Oscillators

Abstract: A theory is presented which predicts the behavior of any self-limiting oscillator in the presence of an injected sinusoidal voltage or current of small but constant magnitude. The internal mechanism responsible for synchronization is not needed, and the theory is thus applicable to any source of alternating current. Experimental verification of the theory is presented for the case of a low-power Hartley oscillator operating at 11.5 Mc. The theory is extended to include the mutual synchronization of two oscillators of arbitrary properties, and applied to a number of examples to indicate briefly the properties of a synchronized oscillator when used as (a) a linear voltmeter for small voltages, (b) a field-intensity meter, (c) a linear a.m. demodulator for small signals, (d) an f.m. demodulator, and (e) a synchronous amplifier-limiter. The use of a synchronized oscillator is of particular interest because microwave generators can be used in addition to the more conventional triode oscillators.

Tunable antenna matching circuit

Abstract: A tunable antenna matching circuit is provided. The matching circuit includes a ferro-electric tunable component. A control signal is applied to the tunable component, changing the component's impedance. This changes the impedance of the matching circuit.

Theoretical and Experimental Investigation of Switching Ripple in the DC-Link Voltage of Single-Phase H-Bridge PWM Inverters

Abstract: Direct current (DC)-link voltage ripple analysis is essential for determining harmonic noise and for DC-link capacitor design and selection in single-phase pulse-width modulation (PWM) inverters. This paper provides an extensive theoretical analysis of DC-link voltage ripple for full-bridge (H-bridge) inverters, with simulation and experimental verifications, considering a DC source impedance (non-ideal DC voltage source). The DC voltage ripple amplitude is theoretically estimated as a function of the output current, both amplitude and phase angle, and the modulation index. It consists of a switching frequency component and a double-fundamental frequency component (i.e., 100 Hz), thereby both components are considered in the analysis. In particular, the peak-to-peak distribution, maximum amplitude, and root mean square (RMS) values of the voltage switching ripple over the fundamental period are obtained. Based on the DC voltage requirements, simple and effective guidelines for designing DC-link capacitors are obtained.

Power system applications for phasor measurement units

Abstract: State-of-the-art technology now permits measurement and analysis of power system performance on a scale not previously possible. Synchronized sampling, derived from the GPS (Global Positioning System), and high accuracy sigma-delta analog-to-digital converters form the basis for a system that can measure the state of the power system at a given instant over any area. Samples are acquired 12 times per cycle and are processed by a recursive discrete Fourier transform (DFT) algorithm. This produces the magnitude and angle of the input signal for each sample. The resulting phasors can be combined to produce a positive sequence phasor for a set of three phase inputs. The positive sequence quantities can be used to calculate voltage and current phase and magnitude, real and reactive power, frequency, and impedance. Since the positive sequence parameters are acquired at the same instant (within 1 microsecond), the state of the system at the measured nodes is known at the sample time. Applications to fault recording, disturbance recording, transmission and generation modelling verification, and power system stabiliser testing, are discussed. >