Output impedance

About: Output impedance is a research topic. Over the lifetime, 11185 publications have been published within this topic receiving 134949 citations.

HF induction motor modeling using automated experimental impedance measurement matching

Abstract: High-frequency (HF) models of electrical motors and power converters are greatly important for electromagnetic compatibility characterization of electrical drives and for electromagnetic interference (EMI) filter design. In this paper, an accurate and effective method for the characterization and tuning of HF models (150 kHz-30 MHz) for induction motors has been proposed based on experimental measurements of the motor impedance. Impedance measurements have been taken in three different configurations: between all the six winding terminals which are shorted and grounded; between the three input terminals which are shorted and grounded (common mode); and between one input terminal and the other two which are shorted (differential mode). Once an HF motor model structure has been chosen and modeled using a state-space representation, its parameters have been tuned using genetic algorithm to match the real impedance in each corresponding configuration. Comparison between the experimental impedance measurements and the model impedance estimate are shown for all the tested configurations, in order to validate the model within the frequency range of interest for EMI.

Design and control of the phase shift full bridge converter for the on-board battery charger of the electric forklift

Abstract: This paper describes the design and control of phase shift full bridge converter with a current doubler, which can be used for the on-board charger for the lead-acid battery of the electric forklift. Unlike the common resistance load the battery has a large capacitance element and it absorbs the entire converter output ripple current thereby shortening the battery life and degrading the system efficiency. In this paper the phase shift full bridge converter with a current doubler has been adopted to decrease the output ripple current and the transformer rating of the charger. The charge controller is designed by using small signal model of the converter considering the internal impedance of the battery. The stability and performance of the battery charger is then verified by the constant current(CC) and constant voltage(CV) charge experiments using an actual lead-acid battery bank for the electric forklift.

Low noise amplifier (LNA) gain switch circuit

Abstract: A circuit is formed to steer current in and out of an inductive load in a manner that enables an amplifier to provide a plurality of gain steps without modifying an LC time constant for the circuit and, therefore, without modifying the tuning or frequency of oscillation for the circuit. A first group of MOSFETs are coupled in parallel and define the circuit current flow. A second group of MOSFETs are coupled in parallel to each other and in series to an impedance device. A third group of MOSFETs coupled to steer current in and out of the impedance device to affect the output signal coupled to one end of the impedance device. The transistors in the second and third groups of MOSFETs are selectively activated to control the amount of current that goes through the impedance device.

Novel SQUID Current Sensors With High Linearity at High Frequencies

Abstract: We have developed novel SQUID current sensors consisting of a sensitive 16-SQUID input stage followed by an output stage of 40, 160, or 640 low-inductance SQUIDs. A highly gradiometric design of the individual SQUIDs with ap 5 mum maximum linewidth makes the devices insensitive to external magnetic noise and allows cool-down and operation in the Earth magnetic field. Output current feedback (OCF) is used to increase the linear signal range. When driving a terminated 50 Omega coaxial cable, the sensor with 160 output SQUIDs exhibits a signal range of one flux quantum Phi0 at a power dissipation of about 100 nW. At 10 MHz and 4.2 K, a total flux noise level of 0.34 muPhi0/radic(Hz) is achieved corresponding to a dynamic range of plusmn 1.5 times 106 radic(Hz). At higher frequencies, interaction of preamplifier voltage noise with the output cable impedance increases the sensor noise (a general problem in high-speed SQUID systems). The small-signal bandwidth is >200 MHz. A very high slew rate of > 50 Phi0/mus is achieved allowing one to use the full signal range at frequencies up to 16 MHz with a total harmonic distortion below ap1%.

Impedance matched passive radio frequency transmit/receive switch

Abstract: A Radio Frequency (RF) structure services an antenna having a characteristic impedance and includes a differential Power Amplifier (PA), a differential Low Noise Amplifier (LNA), and a balun transformer. The differential PA has a differential PA output with a PA differential output impedance. The differential LNA has a differential LNA input with an LNA differential input impedance. The balun transformer has a singled ended winding coupled to the antenna, a differential winding having a first pair of tap connections coupled to the differential PA output and a second pair of tap connections coupled to the differential LNA input, and a turns ratio of the single ended winding and the differential winding. The turns ratio and the first pair of tap connections impedance match the PA differential output impedance to the characteristic impedance of the antenna. The turns ratio and the second pair of tap connections impedance match the LNA differential input impedance to the characteristic impedance of the antenna.