Showing papers on "Converters published in 1971"

A digital frequency synthesizer

Abstract: A digital frequency synthesizer has been designed and constructed based on generating digital samples of \exp [j(2^{\pi}nk/N)] at time nT . The real and imaginary parts of this exponential form samples of quadrature sinusoids where the frequency index k is allowed to vary (-N/4) \leq K . The digital samples drive digital to analog converters followed by low-pass interpolating filters to produce analog sinusoids. The method is superior to digital difference equations with poles on the unit circle since the noise or numerical inaccuracy remains bounded. The digital technique used consists of factoring the exponential into two table look-ups from an efficiently organized small READ-ONLY memory table and performing a complex multiply to produce the real and imaginary components. A small array multiplier efficiently organized performs the multiplications. The technique lends itself to the production of phase coherent or phase controlled sinusoids because of the indexing arrangement used. In addition finer frequency steps than the READ-ONLY memory allows are available by expanding the indexing register at no increase in inaccuracy.

Analysis and optimal design of self- oscillating dc-to-dc converters

Abstract: A general and exact analysis is presented for a class of selfoscillating dc-to-dc converters which can be modeled by a single-loop nonlinear feedback system. The nonlinearity is assumed to be a hysteresis characteristic; however, it is not required to have odd symmetry. A set of equations is obtained which govern the switching frequency, duty cycle, dc error, and peak-to-peak ripple. Based on these equations, it is possible to predict the general performance and inherent limitations of various circuit configurations. An optimal design procedure for these circuits with respect to a quadratic performance index is suggested. Measured data from several voltage-regulator circuits verify the model chosen and its analysis.

Simplified Dynamic Simulation of HVDC System by Digital Computer Part I - Computer Program

Abstract: The paper presents a dynamic simulation of an HVDC system by digital computer employing converter equations based on averaged values. The converters are represented by perfect dc generators and motors, their outputs are equal to those from real converters with the sixth and higher harmonics being neglected. The converter control circuit of the system is represented by actual hardware. Due to the simplified representation the program enables a considerable saving of computation time with minimal loss of accuracy.

A method for generating some active circuits

Abstract: A novel technique is used to derive networks termed converter-inverter circuits. These are 5-ports that can be used to produce any of the following four basic circuits encountered in active network theory: positive impedance converters, negative impedance converters, positive impedance inverters, and negative impedance inverters. Thus a converter-inverter circuit is a very general network; this generality of the circuit demonstrates that the new technique is very versatile.

On inverters and converters

Abstract: Some theorems concerning positive or negative inverters and converters (generalized gyrators and transformers) are stated. These theorems give general methods of transforming a given inverter (or converter) into other inverters or converters. In particular, all possible terminal voltage-current relations of a basic 4-port, which underlies most realizations of inverters and converters, are determined. These results have implications for the practical realization of integrated inverters and converters.

Phase Converters for Rural Applications

Abstract: Three-phase motors can be satisfactorily operated with phase converters on single-phase power at full load and with good phase balance if the converter is properly selected and applied. The correct phase converter installation is important, and allowance must be made for the changes in the motor-torque characteristics which occur. Data are shown for the torque characteristics of a motor operated on two typical phase converters compared with three-phase operation and the effect of capacitance on the torque characteristics.

Converter station having parallel-connected static converters

Abstract: A converter station for high voltage direct current includes two substantially identical parallel converter branches provided with control systems therefore which limit the control angles of the converters of the branches upwards or downwards. A balancing arrangement is provided to assure equal current distribution between the two converter branches when they are forced so far in one direction that the limit value emitter for the converters of one of the converter branches becomes active. The balancing arrangement includes a device responsive to the difference between the current in the two branches to regulate the control system of the converter of the other branch. This arrangement may include cross connections between the limit value emitters to control converters of both converter branches.

Simple negative-impedance convertor

Abstract: The use of controlled (dependent) current sources in designing negative-impedance converters (n.i.c.) is well known. A simple d.c.-coupled n.i.c. circuit which has temperature-compensating features is described.

Active RC Synthesis of Driving Impedances, Generalized Impedance Inverters/Converters, Oscillators and Filters

Abstract: Simple feedback concepts are used to synthesize driving impedances, generalized impedance inverters/converters and oscillators using voltage controlled voltage sources and RC elements. They lead to several new circuits. Some of these are suitably modified to obtain high Q active filters with minimum sensitivity.