Showing papers on "Impulse generator published in 2009"

Evaluation of breakdown characteristics of gas insulated switchgears for non-standard lightning impulse waveforms - method for converting non-standard lightning impulse waveforms into standard lightning impulse waveforms -

Abstract: To lower the lightning impulse withstand voltage of gas insulated switchgear (GIS) while maintaining the high reliability of its insulation performance, it is important to define in an organized way the insulation characteristics for non-standard lightning impulse voltage waveforms that represent actual surge waveforms in the field and compare them with the characteristics for the standard lightning impulse waveform quantitatively. In the preceding researches, lightning surge waveforms and disconnector switching surge waveforms at UHV, 500 kV, and 275 kV substations were analyzed and five to six kinds of non-standard lightning impulse waveforms with basic frequencies of 0.6 to 5.0 MHz were identified. Then, the dielectric breakdown voltage iquest time characteristics were measured under several different conditions on the quasi-uniform SF6 gas gaps and partly the coneshaped insulating spacers that represent insulation elements of GIS for six kinds of nonstandard lightning impulse waveforms. In this paper, the resultant breakdown voltages were evaluated in terms of the overvoltage duration, which led to their formulation in a unified way. On the basis of these insulation characteristics and their unified formulation, the paper investigated a method for converting non-standard lightning impulse waveforms into standard lightning impulse waveforms with equivalent stress for the insulation. When the constructed algorithm was applied to five examples of representative two type waveforms in the lightning surge time region, they were converted into standard lightning impulse waveforms with crest values reduced by 20% to 34%, suggesting potentiality for reduction of lightning impulse insulation specifications of GIS.

Off-line and on-line pd measurements on induction motors fed by power electronic impulses

Abstract: Partial Discharge (PD) off- line and on-line measurements are required to prevent early failures on low voltage induction motors fed by inverter drives. Conventional methods use commercial Digital Scopes to visualize simultaneously the waveform of the applied impulsive voltage and the acquired PD pulses, as well as appropriate solutions to attenuate power electronic voltage impulses. A new approach is proposed in this paper, relying upon a Phase-Resolved PD (PRPD) pattern, which constitutes a simple and efficient tool for PD activity detection in adjustable speed drives. Off-line PD measurements were done on low voltage induction motors fed by a voltage impulse generator and detecting PD Inception Voltage (PDIV) on each phase. Then, PD on line measurements were carried out using a commercial PWM inverter and showing interesting correlation between off-line and on-line tests. All the measurements were performed using antenna sensors, achieving excellent sensitivity.

Self-powered, piezo-surface acoustic wave apparatus and method

Abstract: An autonomous, self-powered device includes a radioisotope-powered current impulse generator including a spring assembly comprising a cantilever, and a piezoelectric-surface acoustic wave (P-SAW) structure connected in parallel to the current impulse generator. Positive charges are accumulated on an electrically isolated 63 Ni thin film due to the continuous emission of β-particles (electrons), which are collected on the cantilever. The accumulated charge eventually pulls the cantilever into the radioisotope thin-film until electrical discharge occurs. The electrical discharge generates a transient magnetic and electrical field that can excite the RF modes of a cavity in which the electrical discharge occurs. A piezoelectric-SAW resonator is connected to the discharge assembly to control the RF frequency output. A method for generating a tuned RF signal includes inputting an energy pulse to a P-SAW resonator, exciting the resonant frequency thereof, and outputting an RF signal having a frequency tuned to the resonator frequency.

Evaluation of K-factor based on insulation characteristics under non-standard lightning impulse waveforms

Abstract: The IEC, which defines the lightning impulse test methods for electric power equipment, is about to introduce the K-factor method for evaluating overshoot of lightning impulse waveforms. There is an urgent need to examine the K-factor method using such parameters as the types and sizes of insulating media and structures. This paper evaluates the K-factor method in the "high-voltage test techniques" using the insulation characteristics of overshoot waveforms in non-standard lightning impulse waveforms. The insulation elements of oil-immersed transformers and gas-insulated switchgear (GIS) used in this study are oil gaps, turn-to-turn insulations, and gas gaps (field utilization factor ? = 0.45 and 0.60), all of which showed results close to the proposed K-factor curve.

Evaluation of breakdown characteristics of gas insulated switchgears for non-standard lightning impulse waveforms - breakdown characteristics in the presence of bias voltages under non-uniform electric field

Abstract: To lower the lightning impulse withstand voltage of gas insulated switchgear (GIS) while maintaining the high reliability of its insulation performance, it is important to define in an organized way the insulation characteristics for non-standard lightning impulse voltage waveforms that represent actual surge waveforms in the field and compare them with the characteristics for the standard lightning impulse waveform quantitatively. In the previous work, the dielectric breakdown voltage - time characteristics were measured under several different conditions on the quasi-uniform SF6 gas gap and partly the cone-shaped insulating spacers that represent an insulation element of GIS for six kinds of non-standard lightning impulse waveforms associated with lightning surges and disconnector switching surges. This paper, describes detailed examination in non-uniform electric field, and the pattern in which a disconnector switching surges are superposed on residual DC elements generated through the operation of disconnectors (bias voltages). This is intended to simulate more severe conditions in an actual system. Consequently, it was found that the presence of a bias voltage in the nonuniform electric field resulted in lower breakdown voltage values for single-frequency oscillation waveforms both in the positive and negative polarities. However, the breakdown voltage values under positive-polarity waveforms posing more severe insulation conditions were higher than the ones under the standard lightning impulse waveforms. Despite the presence of a bias voltage, it was possible to evaluate these breakdown voltage values in the positive polarity using the concept of a duration examined in the past.

Experiment investigation of partial discharges under impulse voltage

Abstract: Partial discharge is defined by IEEE as an electrical discharge that only partially bridges the insulation between conductors and that may or may not occur adjacent to a conductor. Partial discharges occur when the local electrical field intensity exceeds the dielectric strength of the dielectric involved, resulting in localized ionization and breakdown. Therefore, measurement and analysis of this discharge can provide an early warning of insulation failures in equipment. Tests are supposed to anticipate stresses under service conditions and to reveal weak points. Such a means of quality check without doing harm by its application is the partial discharge measurement. This work presents a measuring system for PDs under impulse voltage. Based on a coupling device adapted for this kind of voltages and a method for removing contributions from the applied voltage. The potential of the system has been demonstrated through measurements of PDs around a needle to plane in air under lightning impulse and switching impulse voltages The observations obtained with this PD source prove that the measuring technique described enables detailed studies of PD properties under lightning and switching impulse voltages. This paper presents the characteristics of PD with the needle to plane in air under the impulse voltage in the laboratory.

Gas impulse blower

Abstract: A gas impulse blower for cleaning a surface within a vessel is fillable with a combustion gas-oxidizer mixture. The blower comprises: (a) a combustion assembly configured to generate a deflagration wave; and (b) an impulse generator having an inlet and an outlet and adapted to receive the deflagration wave into said inlet and eject the wave from said outlet onto a surface to be cleaned. The impulse generator has a compartmentalized housing comprising at least two serially-connected compartments. The compartments are configured for being fed with said gas-oxidizer mixture by the combustion assembly in an individual manner so as to conduct the wave to the outlet.

Pneumatic impulse wrench with operation control means

Abstract: A pneumatic impulse wrench for tightening screw joints comprises a housing (10) with a pressure air inlet passage (28), an exhaust air outlet passage (29), a rotation motor, a hydraulic impulse generator, and connections for an air supply conduit (17) and an electric cable (20) for connecting the impulse wrench to a stationary programmable control unit (25). The impulse wrench also includes a torque indicating means connected to the control unit (25) for feed back electric signals responsive of the output torque of the wrench, an electromagnetically activated inlet valve (30) arranged in the air inlet passage (28), and an electromagnetically activated exhaust valve (22) controlling the exhaust air flow from the motor, wherein the exhaust valve (22) is a proportional valve activated by a linearly operated electromagnetic actuator (36) and arranged to continuously adapt the exhaust air flow and, hence, the motor power to the characteristics of the actual screw joint being tightened in response to feed back signals from the torque indicating means and in accordance with a programmed tightening strategy.

High pressure impulse generator based on triple-pole ignition switch

Abstract: The utility model relates to a high voltage impulse generator, in particular to an impulse generator based on a triple-pole ignition switch. The high voltage impulse generator solves the problem of the prior impulse generator such as large single impulse energy. The high voltage impulse generator comprises a voltage boost circuit for converting 220 V alternating current voltage input into 30 kV direct current voltage and outputting the 30 kV direct current voltage to a discharge capacitor, a triple-pole ignition switch high voltage impulse control circuit for generating control impulse signals of controlling high-voltage impulse and outputting the control impulse signals to a discharge circuit; the direct current voltage positive output end of the voltage boost circuit is connected with one end of a current limiting resistance; the other end of the current limiting resistance is simultaneously connected with one end of the discharge capacitor and the solid electrode of the triple-pole ignition switch; the other end of the discharge capacitor is connected with a power ground; the hollow electrode of the triple-pole ignition switch is simultaneously connected with the cathode of a discharge silicon stack and one end of a load; the anode of the discharge silicon stack is connected with the power ground; the other end of the load is connected with the power ground; and the triggering needle of the triple-pole ignition switch is connected with the impulse signal output end of the high voltage impulse control circuit.

Effects of Impulse Voltage Waveforms on Lightning Shielding Simulation Test of Transmission Lines

Abstract: In order to make a research on the effects of impulse voltage waveforms on lightning shielding property of transmission lines, this paper adopted the model of 500 kV transmission lines in plain country at the ratio of 1:40. Large amount of impulsive discharge tests were done, including lightning surge voltage and switching impulse voltage. The scattergram of shielding failure probability of lightning stroke points in space is plotted, and the distribution rule is in close agreement with the results calculated by EGM model. The shielding failure probability is calculated by two methods according to the simulation test results, and the results are compared with the results calculated by order method and LPM method. Comparative result shows that test with switching impulse voltage is closer to the reality than test with lightning surge voltage when the length of the air gap is the same.

Current and voltage distribution in a horizontal earth electrode under impulse conditions

Abstract: In this paper, the behaviour of a horizontal electrode under impulse conditions is investigated experimentally at the Cardiff University outdoor earthing test facility. The test electrode consists of 88.5m long copper conductor buried to a depth of 30cm, and is divided into sections with test pits located along the electrode to enable access for voltage and current measurements along its length. A test circuit is established using an auxiliary current electrode, and a low voltage impulse generator is used to inject current of different magnitudes and shapes into the test electrode. The effect of current injection location, electrode length and current rise time is quantified on the current and earth potential rise (EPR) distribution along the electrode. The measured voltage and current signals were analysed at various points on the electrode to determine the effective length. Good agreement between measured and computed values was obtained. Based on an analysis of the results, the effective length of a horizontal electrode under the particular test conditions was determined and good agreement between measured and computed values was obtained.

Si/SiGe HBT UWB impulse generators with sleep-mode targeting the FCC masks

Abstract: In this paper two UWB impulse generator ICs are presented, targeting the FCC ultra-wideband spectral masks for indoor and outdoor communications. For the generation of the impulse an underdamped RLC resonance circuit is excited by a short current spike. An on-chip power down circuit, consisting of a Widlar bandgap reference and several current mirrors was included, allowing to completely switch off the ICs with a single control signal under full DC biasing. The impulses show a very short time-domain extension and neglibile excess ringing, allowing high repetition rates, exceeding the 400MHz shown in this paper. The two impulse generators exhibit peak amplitudes of 170 and 180mV and the full-width at half maximum of the time domain waveforms are below 200 and 260 ps, respectively. All circuit blocks were realized using 0.8µm Si/SiGe NPN HBTs only.

Impulse based range-gated UWB wireless transceiver IC in 90nm CMOS for medical sensing applications and communications

Abstract: This paper presents a new impulse based ultra-wide band (UWB) transceiver system designed in 90nm CMOS technology for UWB medical radar sensing and communication applications. The design is targeting for human heart motion detection and short range data communications. The transmitter is composed of a simple on-off keying (OOK) modulated impulse generator and a variable gain-controlled amplifier (VGA) at the transmitter. The generated pulse width can be adjusted. The receiver operating in the radar mode is composed of a simple low noise amplifier, a mixer, and an analog-to-digital converter operating in the radar mode. The range gate control design allows the receiver gather maximum power reflection from the objects within the expected range and minimizes the noise. The proposed impulse based UWB transceiver works under a 1.2V power supply and the transmitter provides an output transmitting pulses of 300mV to 50Ω load. The fully integrated UWB transceiver occupies a core area of 0.3mm2. The transceiver works in UWB band of 3.1–6GHz and consumes an average power of 5.32mW and 12.69mW for simulations of radar sensing and communications, respectively.

Corona Charged Subnanosecond Impulse Generator

Abstract: An impulse generation system based on the floating electrodes corona charging mechanism is presented. Measurement results demonstrate that it is possible to obtain sub nanosecond impulses with this novel charging technique.

Generation of sub-nanosecond 7V Gaussian pulse using GaAs HBT with 3V battery supply

Abstract: A new sub-nanosecond high power impulse generator is presented in this paper for ultra-wideband communication and radar systems using InGaP/GaAs HBT technology. The topology is simple, compact and can be readily integrated into MMIC. It works on two principles: a faster transition can be obtained from a digital logic input into the HBT and a differentiation of the very fast transition current using the inductor to generate a large voltage at the output. Measurement results show the generated Gaussian pulse has a tunable peak voltage between 1 V to 7 V with full-width-half-maximum (FWHM) between 200 ps to 250 ps. The impulse generator is biased at 3 V battery supply and consumes 27 mW to generate a 7 V high 250 ps wide Gaussian impulse at a 1 MHz pulse repetition rate (PRF).

FM over impulse radio UWB

Abstract: Recent regulatory action provided access to large chunks of spectrum for low spectral power density ultra-wideband communication and sensing devices, yet use of this spectrum currently lags behind expectations. The authors propose a simple migration path suitable for low-cost analog audio and video distribution. It uses FM modulation of the clock signal to an impulse radio pulse generator and a simple receiver based on a rectifier or squaring device which retrieves the FM modulated signal. Using previously developed IR-UWB components (an FCC-compliant monolithic pulse generator, a 3.1–10.6GHz low-noise amplifier and wideband antennas), plus discrete receiver components, a proof-of-concept experiment was conducted with a 99.4MHz carrier frequency FM signal. Furthermore it is shown that the receiver performance can be further improved by properly terminating the higher-order signal components after the rectifier.

A CMOS ultra-wideband impulse generator for 22–29 GHz automotive radar application

Abstract: This paper presents the design and simulation of a CMOS ultra-wideband pulse generator using IBM 90nm CMOS technology. The operating frequency band of the pulse generator is from 22 to 29 GHz for the application of short-range automotive radar. The pulse generator has a simple architecture using digital circuits. The simulation results show that the power spectral density of the pulse generator has a center frequency of 24.4 GHz and has a -10 dB bandwidth from 22 to 29 GHz.

Study on the Transfer Overvoltage Test of Capacitor Voltage Transformer

Abstract: Transfer overvoltage test is difficult to achieve in instrument transformers' detection.Due to the large capacitance of capacitor voltage transformer(CVT),test of transfer overvoltage is more difficult.By way of analysis,study and calculation of the test circuit of the impulse voltage generator,A-type transfer overvoltage impulse wave of CVT meeting the standard requirements has been obtained,and the transfer characteristic has also been preliminarily investigated in this paper.

A pulse generator UWB-Ultra Wide Band using PFD Phase Frequency Detector in 180nm CMOS technology

Abstract: This paper presents a design of a transmitter pulse generator UWB-Ultra Wide Band in standard 180nm MOSIS/CMOS technology. We proposed a pulse generator using Phase-Frequency Detector (PFD) that is designed using a modified architecture TSPC (True Single-phase Clock) positive edge triggered D Latch. The operation range and power consumption PFD is 45µW to 2mW, from 200MHz to 5GHz, respectively, and a minimum phase difference is 30ps. Whole circuit has been simulated using LTSpice and the results had demonstrated the circuit capability to operate as an impulse generator. It generates pulses with 70ps width. The Gaussian impulse achieves a very short pulse width of 133ps, and amplitude of 48mV. The generated pulse shape is similar to the 1st derivative. The complete design, occupies an area of 35400µm2 including the inductor and without the PAD`s and a power consumption of 2mW at 2.56GHz@ 2V supply voltage.

Lightning Impulse Ageing of HV Cable Insulation

Abstract: Lightning impulses can lead to accelerated ageing of extruded cables. Electrical behaviour of a dielectric material when experiencing a lightning impulse is different to that for DC or power frequency applied voltages. Pre-designed shaped HDPE material samples have been manufactured using a mould tool. The samples then have been electrically aged using an impulse generator. A real-time software based monitoring tool has been designed to control the impulse wave-shape and process the measurement data. Sets of identical lightning impulses were applied to samples and this was then followed by ramped AC breakdown tests. The obtained results were analyzed using Weibull distribution to identify any differences in lifetime between aged and unaged samples. Measurements of dielectric loss and space charge were also undertaken to identify the impulse ageing mechanism.

Apparatus Used to Measure Grounding Resistance Based on the Impulse Current

Abstract: Impulse grounding resistance is one of important parameters for safe operation of power system and electronic equipment.A measurement apparatus used to measure impulse grounding resistance is introduced.While injecting impulse current with sharp wave head as the test current into grounding systems,the current and voltage signals collected are transformed by Fast Fourier Transform(FFT),then impulse grounding impedance,resistance and inductance component can be calculated.The apparatus used to measure impulse impedance consists of microcontroller-ELANSC520/133,CPLD and high-speed analog-to-digital converter,and program development are introduced.Finally,simulation test result and field measuring result are given,which proves that the device is reliable.The apparatus has such advantages as small volume,stabilization.In addition,the apparatus can store wave shape and has the communication function.It can completely meet the demand to measure.

Design and construction of a corona charged high power impulse generator

Abstract: A prototype of an impulse generation system based on a corona current charging mechanism is presented. The system is capable of delivering 30 kV short pulses of about 1 ns of rise time. To simulate the generator pulse repetition frequency an electric model based on the unipolar corona charge current approximation was developed. The results obtained using the developed model are compared with experimental data showing good agreement.

Multi-level impulse sequence control device for switch power supply in pseudo continuous work mode

Abstract: A multi-level impulse sequence control device for a switch power supply operated in a pseudo continuous work mode is structurally characterized in that a voltage detecting circuit, an error amplifier, an error burst judging device, a multi-level impulse generator and a driving circuit are sequentially connected, a clock signal generator and the error burst judging device are connected with the multi-level impulse generator, and the current detecting circuit is connected with the multi-level impulse generator The multi-level impulse sequence control device can realize multi-level impulse sequence control of the switch power supply in a pseudo continuous work mode By utilizing the control device, output power of a converter is not limited by current critical conditions Further, the multi-level impulse sequence control device is relatively low in output voltage ripples, fine in dynamic response and strong in anti-interference ability, and is adaptable to converters of various topological structures

A current-steering DAC-Based CMOS ultra-wideband impulse generator

Abstract: In this paper, the design and simulation of a CMOS ultra-wideband pulse generator using TSMC 0.18µm CMOS technology is presented. The operating frequency band of the pulse generator is from 3 to 10 GHz for the application of ultra-wideband (UWB) communications. The structure of the impulse generator is based on the current-steering digital-to-analog converter (DAC). The impulse generator has the feature of high-tunability and the simulation results show that the output of the impulse generator complies with the FCC regulations and has a power consumption of 27mW at a 50 MHz pulse repetition rate (PRR).

Effects of Lightning Impulses on the Dielectric Properties of HDPE

Abstract: Impulse over-voltages are very common phenomena in electric power systems. Switching impulses are created by switching surges or local faults while lightning impulses are due to lightning strikes to overhead lines. Both impulses can travel as waves in the system, damaging insulation components and equipment. This paper shows that there may well be a reduction in electric field strength of the insulation of a power cable that experiences a lot of lightning impulse over-voltages. The paper also provides insight into the dominant ageing processes through the analysis of dielectric spectroscopy measurement data.

Electronic ballasting method of gas discharge lamp and ballast thereof

Abstract: The invention relates to an electronic ballasting method of a gas discharge lamp; a start high frequency impulse is generated by a control unit and a high power chopper of a power conversion unit is driven by the control unit; after alternating current is rectified the full-wave, a pulsating direct current is processed by high frequency chopping of high power chopper and by transformation, after passing through a high frequency inductor, a high pressure trigger is started by the obtained pulsating direct current and a start high frequency alternating current is outputted. A power supply high frequency impulse is produced in the control unit and high frequency alternating current energy is provided continuously in a new frequency by the power conversion unit. The invention also provides an electric ballast of the gas discharge lamp, comprising a control unit and a power conversion unit; the control unit is composed of an impulse generator, a pulse distributor, a power driver, a high frequency transformer and a adjustment protection unit; the power conversion unit is composed of a rectifier, a high frequency chopper, a high frequency transformer, a high frequency inductor, a high frequency current transformer and a high pressure trigger. The invention solves the problems of the reliability and stability of the electronic ballast and the energy saving.

Partial Discharge Measurement and Analysis of Gap in Oil-Paper Insulation Model under Lightning Impulse Voltage

Abstract: To investigate the partial discharge(PD) characteristic of the gap in oil-paper insulation model under lightning impulse voltage,the PD mechanisms of the gap in oil-paper insulator under impulse voltage are analyzed with three-capacitor model.The gap in oil-paper insulation model and PD measurement system under impulse voltage are designed.The PD pulses are analyzed and processed by ORIGIN numerical analysis software.The waveform feathers of the main PD pulse in the front time and other PD pulse during wave tail time are described.The parameters of the partial discharge inception voltage(PDIV) and discharge repetition rate on average are discussed.The results indicate that there are main PD pulse and repeated PD pulses in the front and tail time under lightning impulse voltage,the waveform of lightning impulse voltage is of high frequency and random so PD pulses are always superimposed by a voltage from the capacitive current.This study may provide theoretical and practical bases for the insulation evaluation of power equipment.

Simultaneous impulse stimulation and response sampling technique for built-in self test of linear analog integrated circuits

Abstract: This paper proposes a new impulse stimulation and response sampling technique for the implementation of a Built-In Self Test of linear analog integrated circuits embedded in mixed-signal systems. The testing technique is the monitoring of physical fault influences on impulse response characteristics through the use of single-point sampling method and window criterions. The implementation of BIST system realizes a controllable impulse generator, which provide two short impulses simultaneously for stimulating a Circuit-Under-Test, and sampling a transient impulse response. This proposed technique is cost-effective and relatively compact. Neither high-precision analog test stimuli with fault-free bit streams nor characterization and synchronization processes in DSP are required. Demonstrations of the BIST system for a Sallen-Key low-pass filter in a physical level using 0.18-μm CMOS technology show a low area overhead of 11.19%, and offer high catastrophic and parameter fault coverage of 98.24%.