Accurate Extraction of Noise Source Impedance of an SMPS Under Operating Conditions

An accurate measurement method to extract the common mode (CM) and the differential mode (DM) noise source impedances of a switched mode power supply (SMPS) under its operating condition is developed and validated. With a proper pre-measurement calibration process, the proposed method allows extraction of both the CM and the DM noise source impedances with very good accuracy. These noise source impedances come in handy to design an electromagnetic interference (EMI) filter for a SMPS systematically with minimum hassl

Using transfer ratio to evaluate EMC design of adjustable speed drive systems

This paper proposes a way to evaluate the conducted electromagnetic compatibility performance of variable speed drive systems. It is considered that the measured noise level is determined by two factors, the level of the noise source and the conversion efficiency of the propagation path from the source to the measurement equipments. They are corresponding to the two roles played by the converter. On the one hand, a converter provides the noise source and generates the noise current and voltage on the motor side with the cable and the motor. On the other hand, it acts as the propagation path with the DC bus and the rectifier to spread the noise generated on the motor side to the line side. The transfer ratio is defined as the ratio between the CM current on the motor side and the CM current on the line side. It can be used to evaluate the EMC design of a converter because it is independent of the cable and the motor. A simplified model is used to explain this characteristic. It can be measured when the converter is powered off. Verification is carried out by experimental results obtained from a 12-kVA laboratory system.\u

A Single-Stage LED Driver Based on ZCDS Class-E Current-Driven Rectifier as a PFC for Street-Lighting Applications

This paper presents a light-emitting diode (LED) driver for street-lighting applications that uses a resonant rectifier as a power-factor corrector (PFC). The PFC semistage is based on a zero-current and zero-derivative-switching (ZCDS) Class-E current-driven rectifier, and the LED driver semistage is based on a zero-voltage-switching (ZVS) Class-D LLC resonant converter that is integrated into a single-stage topology. To increase the conduction angle of the bridge-rectifier diodes current and to decrease the current harmonics that are injected in the utility line, the ZCDS Class-E rectifier is placed between the bridge-rectifier and a dc-link capacitor. The ZCDS Class-E rectifieris driven by a high-frequency current source, which is obtained from a square-wave output voltage of the ZVS Class-D LLC resonant converter using a matching network. Additionally, the proposed converter has a soft-switching characteristic that reduces switching losses and switching noise. A prototype for a 150-W LED street light has been developed and tested to evaluate the performance of the proposed approach. The proposed LED driver had a high efficiency (>91%), a high PF (>0.99), and a low total harmonic distortion (THD i <; 8%) under variation of the utility-line input voltage from 180 to 250 V rms . These experimental results demonstrate the feasibility of the proposed LED scheme

A fiber-optic current sensor for aerospace applications

A robust, accurate, broad-band, alternating current sensor using fiber optics is being developed for space applications at power frequencies as high as 20 kHz. It can also be used in low and high voltage 60 Hz terrestrial power systems and in 400 Hz aircraft systems. It is intrinsically electromagnetic interference (EMI) immune and has the added benefit of excellent isolation. The sensor uses the Faraday effect in optical fiber and standard polarimetric measurements to sense electrical current. The primary component of the sensor is a specially treated coil of single-mode optical fiber, through which the current carrying conductor passes. Improved precision is accomplished by temperature compensation by means of signals from a novel fiber-optic temperature sensor embedded in the sensing head. The technology contained in the sensor is examined and the results of precision tests conducted at various temperatures within the wide operating range are given. The results of early EMI tests are also given

Digital frequency domain multiplexing readout electronics for the next generation of millimeter telescopes

Frequency domain multiplexing (fMux) is an established technique for the readout of transition-edge sensor (TES) bolometers in millimeter-wavelength astrophysical instrumentation. In fMux, the signals from multiple detectors are read out on a single pair of wires reducing the total cryogenic thermal loading as well as the cold component complexity and cost of a system. The current digital fMux system, in use by POLARBEAR, EBEX, and the South Pole Telescope, is limited to a multiplexing factor of 16 by the dynamic range of the Superconducting Quantum Interference Device pre-amplifier and the total system bandwidth. Increased multiplexing is key for the next generation of large format TES cameras, such as SPT-3G and POLARBEAR2, which plan to have on the of order 15,000 detectors. Here, we present the next generation fMux readout, focusing on the warm electronics. In this system, the multiplexing factor increases to 64 channels per module (2 wires) while maintaining low noise levels and detector stability. This is achieved by increasing the system bandwidth, reducing the dynamic range requirements though active feedback, and digital synthesis of voltage biases with a novel polyphase filter algorithm. In addition, a version of the new fMux readout includes features such as low power consumption and radiation-hard components making it viable for future space-based millimeter telescopes such as the LiteBIRD satellite.Comment: 15 pages, 10 figures. To be published in Proceedings of SPIE Volume 9153. Presented at SPIE Astronomical Telescopes + Instrumentation 2014, conference 915

New Modulation Technique to Mitigate Common Mode Voltage Effects in Star-Connected Five-Phase AC Drives

Star-connected multiphase AC drives are being considered for electromovility applications such as electromechanical actuators (EMA), where high power density and fault tolerance is demanded. As for three-phase systems, common-mode voltage (CMV) is an issue for multiphase drives. CMV leads to shaft voltages between rotor and stator windings, generating bearing currents which accelerate bearing degradation and produce high electromagnetic interferences (EMI). CMV effects can be mitigated by using appropriate modulation techniques. Thus, this work proposes a new Hybrid PWM algorithm that effectively reduces CMV in five-phase AC electric drives, improving their reliability. All the mathematical background required to understand the proposal, i.e., vector transformations, vector sequences and calculation of analytical expressions for duty cycle determination are detailed. Additionally, practical details that simplify the implementation of the proposal in an FPGA are also included. This technique, HAZSL5M5-PWM, extends the linear range of the AZSL5M5-PWM modulation, providing a full linear range. Simulation results obtained in an accurate multiphase EMA model are provided, showing the validity of the proposed modulation approach.This work has been supported in part by the Government of the Basque Country within the fund for research groups of the Basque University system IT978-16 and in part by the Government of the Basque Country within the research program ELKARTEK as the project ENSOL (KK-2018/00040)

Reliability and maintainability assessment factors for reliable fault-tolerant systems

A long term goal of the NASA Langley Research Center is the development of a reliability assessment methodology of sufficient power to enable the credible comparison of the stochastic attributes of one ultrareliable system design against others. This methodology, developed over a 10 year period, is a combined analytic and simulative technique. An analytic component is the Computer Aided Reliability Estimation capability, third generation, or simply CARE III. A simulative component is the Gate Logic Software Simulator capability, or GLOSS. The numerous factors that potentially have a degrading effect on system reliability and the ways in which these factors that are peculiar to highly reliable fault tolerant systems are accounted for in credible reliability assessments. Also presented are the modeling difficulties that result from their inclusion and the ways in which CARE III and GLOSS mitigate the intractability of the heretofore unworkable mathematics

Britain's first computer centre for banking: What did this building do?

At the beginning of the 1960s Barclays became the first British bank to open a computer centre. In this paper I trace the life of this building starting with its official opening on 4 July 1961 and ending with its protracted closure a decade later. From initial status as the most advanced bank bookkeeping system in the world serving as a highly visible symbol of the bank's technological power, to a final repurposing of its grandiose reception as a distribution point for pre- and post-decimalisation output, the building's various meanings are revealed. Making use of written, oral, and visual sources I explore the centre's spatial characteristics, its relation to the distributed structure of the branch, and its place as a first dedicated working home for a newly emerging computing subculture. A blend of multiple perspectives internally from the top down and bottom up, and externally from customer and competitor, offer an analysis that uncovers the part played by the first computer centre place in the banking automation race

Preliminary study, analysis and design for a power switch for digital engine actuators

Innovative control configurations using high temperature switches to operate actuator driving solenoids were studied. The impact on engine control system life cycle costs and reliability of electronic control and (ECU) heat dissipation due to power conditioning and interface drivers were addressed. Various power supply and actuation schemes were investigated, including optical signal transmission and electronics on the actuator, engine driven alternator, and inside the ECU. The use of a switching shunt power conditioner results in the most significant decrease in heat dissipation within the ECU. No overall control system reliability improvement is projected by the use of remote high temperature switches for solenoid drivers