Showing papers on "Negative impedance converter published in 1970"

Brushless dc adjustable speed drive with static regenerative dc motor control

Abstract: For a brushless direct current motor there is provided a static adjustable speed control circuit including an SCR converter for controlling the average voltage applied to the motor windings by phase control of current flowing directly from a multi-phase power source and for commutating the current through the motor winding to maintain the proper current flow direction and torque. The SCR converter is controlled as a function of rotor position, a-c line input conditions, phase advance and SCR converter voltage output. A voltage feedback signal from the converter output is compared to a reference voltage to derive a comparison signal used to adjust the phase advance and thereby control the average voltage applied to the motor terminals. The polarity of the comparison signal determines whether motoring action or regeneration is to occur. Current feedback from the input lines is used to prevent combinations of SCRs from ''''turning on'''' and short circuiting the load.

Analysis of Synchronous Machines under Unbalanced Operation

Abstract: Considering only the fundamental frequency components of currents and voltages, an idealized synchronous machine under any unbalanced load conditions can be represented in phase coordinates, by the sum of a constant impedance matrix and an impedance matrix whose elements are functions of current phase angles. A general method of solving for the unknown current phase angles and hence the total impedance matrix is given when the external impedances are known. The results are shown to be consistent with 1) two-reaction theory for the case of balanced steady- state loads, and 2) symmetrical-component theory using sequence- impedance representation under the assumption of zero resistances in all circuits. Numerical comparison shows that although the current magnitudes can be calculated by the approximate sequence- impedance representation quite accurately, current phase angles could differ, in certain cases, up to about 10°.

A four quadrant multiplier using a single amplifier in a balanced modulator circuit

Abstract: A multiplier circuit, having a relatively constant input impedance, capable of multiplying a positive or a negative input signal by a gain which is variable from a positive to a negative value by varying one control impedance. The input signal is applied to a reference input and to a signal input which includes a feedback path to provide both positive and negative products without the need for additional sign circuits or complimentary signals. The multiplier circuit can be adapted for use as a balanced modulator by providing an analog input signal and switching the control impedance between two different impedance values with a binary carrier signal.

Voltage level shifter circuit with current ratio control of transconductive impedance of semiconductor

Abstract: A voltage level shifter introduces a fixed voltage shift into a transmitted signal by controlling the transconductive impedance of a regulator transistor. The magnitude of the voltage shift is determined by a reference voltage drop established across an impedance energized by a constant-current source. A differentially coupled pair of transistors comprise a feedback network to compare the voltage level shift to the reference voltage and adjust the transconductive impedance of the regulator transistor accordingly. The basic voltage level shifter may be connected symmetrically in a four-terminal circuit arrangement with a common reference voltage control to generate a balanced voltage level shift free of longitudinal drift signals.

Static impedance relay

Abstract: A static impedance relay for controlling a circuit includes a switch operated by a relay coil which is connected to a zero detector. The zero detector is fed with a first pulsating voltage which is proportional to the current supplied and a second voltage which is the algebraic sum of a direct voltage proportional to the voltage supply and a second pulsating voltage adjustably proportional to the voltage supply.

Telephone wire pair compensator utilizing negative capacitance circuit

Abstract: Apparatus is disclosed for compensating a telephone wire pair to alleviate transmission degradation caused by wiring capacitance. A negative capacitance effect is provided by employing positive capacitive feedback around each of two complementary transistor pairs. The pairs are also complementary in conductivity types with respect to each other and are connected effectively in series across a DC potential source so as to operate efficiently and in a balanced manner in a telephone environment.

Method of effecting x-ray analyses

Abstract: To the anode of an X-ray tube a basic direct current voltage is applied, approaching the threshold voltage required for the excitation of the analyzed element, and superimposed on this voltage is a sinusoidal alternating voltage. In the positive portions of the sinusoidal voltage the combined voltage exceeds the threshold voltage, whereas in the negative portions it lies below the same. The contents of the analyzed element is registered by a detector whose electronic evaluating device is selectively sensitive to the third or higher harmonics.

Arrangement for regulating the current supplied to the operative circuit of a commutating motor

Abstract: A control system for a commutating electric motor includes at least one semiconductor controlled element for controlling the current in the operative circuit of the motor and a control device for adjusting the firing angle thereof. A negative feedback regulating voltage is supplied to the control device which depends upon the current in the operative circuit and/or upon the motor speed. Switching transients in the operative circuit are limited by means of a sum voltage composed of a bias voltage and a positive feedback voltage derived in an integrating positive feedback loop. The positive feedback voltage is determined by the voltage across the operative circuit. The switching transients are primarily determined by the bias voltage and the resistance of the operative circuit.

Current or voltage-to-frequency converter using negative feedback

Abstract: A current or voltage-to-frequency converter is provided for converting a DC current or voltage to a proportionate frequency of electrical pulses of predetermined width. The converter includes an integrator coupled to control the frequency of a voltage-controlled oscillator, and negative feedback is provided to the input of the integrator during the occurrence of pulses from the oscillator to provide high linearity and stability.

Circuit Realization of Impedance Loading for Cross Section Reduction

Abstract: : Techniques for realizing a reactance which is a decreasing function of frequency are discussed. A Negative Impedance Converter (NIC) circuit is analyzed and techniques given for compensating for imperfections and frequency dependence. An RC realization of the desired impedance is given, and it is demonstrated that this realization can be modified to compensate for phase shift in the NIC. An analytical and numerical analysis of a NIC based on amplifiers with 50 ohm input and output impedances is presented.

On the Synthesis of RC All Pass Networks

Abstract: A method of synthesizing RC all pass networks of order n⩽2 using a single active element, namely a negative impedance converter, is described. An example has also been presented to illustrate the procedure.