CASE REPORT | doi:10.20944/preprints202111.0102.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: Corona discharge; corona ring; corona suppression; high voltage capacitor banks; shunt capacitor banks
Online: 4 November 2021 (11:21:35 CET)
Capacitor banks are widely used in current electrical transmission systems in order to improve power quality and increase efficiency. Utilizing high voltage components such as, shunt capacitors in the power grid imposes new challenges to the system which are required to be addressed. One of these challenges is corona discharges that can have negative impacts on capacitor banks such as power loss, insulator erosion followed by equipment failure, and radio interference. Although previous studies have almost exclusively focused on optimization of corona suppression rings for transformers and transmission lines, no specific studies have conducted regarding high voltage capacitor banks. This paper presents a novel study concerning verification and development of corona discharge suppression models on AC and DC capacitor banks with two different voltage levels. The employed method is based on the Maxwell’s equations and finite element method (FEM) which is implemented with the help of COMSOL Multiphysics© software. Results have verified the necessity of suppression methods as well as the efficiency of proposed solutions. Corona inception voltage levels are identified and effective factors on its appearance are reviewed. Analyses of proposed solutions have shown significant improvements in optimization of corona suppression methods as well as enhancement of maintenance maneuverability.
ARTICLE | doi:10.20944/preprints202203.0204.v1
Online: 15 March 2022 (10:46:57 CET)
To increase the network computer and mobile telephone capacity one needs a laser to carry information instead of electrons. Since the laser is very fast compared to electrons, one expects information to be transmitted very fast through the network (internet). This requires searching for chips that act as capacitors, inductors, or evens as resistors this work shows that the laser traveling beam diminished as the frequency reciprocal thus acts as a capacitor or diminished as frequency thus acts as an inductor and sometimes diminished with the concentration of carriers thus act as a resistor for magnetic materials with strength that cancels the friction force when the laser frequency is equal nearly to the atoms natural frequency the material act as an inductor. Then frictional force is dominant with high mobility dielectric, the material acts as a capacitor. However, it acts as a conductor for negligible friction and natural frequency.
ARTICLE | doi:10.20944/preprints202009.0364.v1
Subject: Materials Science, Metallurgy Keywords: electro sinter forging; powder metallurgy; capacitor discharge sintering; 100Cr6
Online: 16 September 2020 (12:13:25 CEST)
In this study one of the most innovative sintering techniques up to date was evaluated: Electro-Sinter-Forging (ESF). Despite it has been proved to be effective in densifying several different metallic materials and composites, bearing steels such as 100Cr6 have never been processed so far. Pre-alloyed Astaloy CrM powders have been ad-mixed with either graphite or graphene and then processed by ESF to produce a 100Cr6 equivalent composition. Porosity has been evaluated by optical microscopy and compared to that one of 100Cr6 commercial samples. Mechanical properties such as hardness and transverse rupture strength were tested on samples produced by employing different process parameters and then submitted to different treatments (machining, heat treatment). The experimental characterization highlighted that porosity is the factor mostly affecting mechanical resistance of the samples, correlating linearly to the transverse rupture strength. Hardness on the other side does not correlate to the mechanical resistance because process related cracking has a higher effect on the final properties. Promising results were obtained that give room to the sinterability by ESF of materials difficult to sinter by conventional press and sinter techniques.
ARTICLE | doi:10.20944/preprints202112.0100.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: memristor; emulator; analog design; switched capacitor; stochastic computing; mixed signal
Online: 7 December 2021 (11:41:20 CET)
Due to the increased use of memristors, and its many applications, the use of emulators has grown in parallel to avoid some of the difficulties presented by real devices such as variability and reliability. In this paper, we present a memristive emulator designed using a Switched Capacitor (SC), this is, an analog component/ block and a control part or block implemented using stochastic computing (SCo) and therefore fully digital. Our design is thus a mixed signal circuit. Memristor equations are implemented using stochastic computing to generate the control signals necessary to work with the controllable resistor implemented as switched capacitor.
ARTICLE | doi:10.20944/preprints202206.0363.v1
Subject: Physical Sciences, General & Theoretical Physics Keywords: second law of thermodynamics; photoelectric effect; thermionic emission; thermo-charged capacitor
Online: 27 June 2022 (10:58:00 CEST)
The photoelectric effect induced by blackbody radiation could be a mechanism to harvest ambient thermal energy at a uniform temperature. Here, I describe (without going too much into mathematical details) the theoretical model I developed starting from 2010 to study that phenomenon, and I summarize the results of the numerical simulations. Simulations tell us that the process must be there. Moreover, at least two experimental tests have been performed in the past years that seem to corroborate, although not definitely, the alleged functioning of the proposed mechanism. Unfortunately, at present, the obtainable power density is extremely low and inadequate for immediate practical applications.
ARTICLE | doi:10.20944/preprints201804.0154.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: DC-DC power converter; fault tolerance; multilevel converter; switched-capacitor network
Online: 11 April 2018 (14:18:54 CEST)
A modular switched-capacitor (SC) DC-DC converter (MSCC) is introduced in this paper. It is designed to boost a low input voltage to a high voltage level and can be applied for photovoltaics and electric vehicles. This topology has high extensibility for high voltage gain output. The merits of the converters also lie in the fault tolerance operation and the voltage regulation with a minimum change in the duty ratio. Those features are built in when designing the modules and then integrating these into the DC-DC converter. Converter performance including voltage gain, voltage and current stress are focused and tested. The converter is modelled analytically, and its control algorithm is analyzed in detailed. Both simulation and experiment are carried out to verify the topology under normal operation and fault mode operation.
ARTICLE | doi:10.20944/preprints201610.0074.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: high voltage gain; switch-clamp capacitor; DC–DC converter; renewable energy
Online: 18 October 2016 (09:45:49 CEST)
A high step-up DC-to-DC converter that integrates an isolated transformer and a switched-clamp capacitor is presented in this study. The voltage stress of the main power switch should be clamped to 1/4 V by using the turn ratio and switched-clamp capacitor of an isolated transformer to achieve a high voltage gain. In addition, a passive clamp circuit is employed reduce voltage stress on the main power switch. The energy of the leakage inductor can be recycled by the clamp capacitor because of the passive clamp circuit, thereby improving the power converter efficiency. The converter consists of one isolated transformer, one main switch, three capacitors, and four diodes. Operating principle and steady-state analyses are also discussed. Finally, a 24-V-input voltage to 200-V-output voltage and a 150 W output power prototype converter are fabricated in the laboratory. The maximum efficiency of the converter is 95.1 at 60 W.
ARTICLE | doi:10.20944/preprints202010.0287.v1
Subject: Engineering, Automotive Engineering Keywords: electric field coupling; differential input structure; non-contact voltage measurement; multi-layer ceramic capacitor; transient response
Online: 13 October 2020 (15:41:01 CEST)
Traditional potential transformers have problems of large volume, difficulty in insulation, iron core saturation, ferroresonance overvoltage and poor transient response characteristics. The voltage sensor based on the principle of electric field coupling and differential input structure does not need to contact the measured object or ground, and can avoid the above problems. However, it requires a sufficiently high capacitance between the differential electrodes to obtain sufficient accuracy and a high voltage division ratio. The existing method of using mutual capacitance between the differential electrodes will cause many problems and fail to meet the practical needs. To solve the above problems, this paper innovatively uses multi-layer ceramic capacitor to replace the mutual capacitance and designs a new type of voltage sensor. In addition, by using single bypass small resistance grounding method to increase the input impedance of the differential signal processing circuit, error of the sensor is further reduced. The experimental results show that the sensor has excellent accuracy and great transient response characteristics. The ratio error under power frequency is within ±0.5% and the phase error is within 1. The ratio error in the range of 500 Hz∼30 kHz is within ±5% and the phase error is within 5. Moreover, it has the advantages of low cost, miniaturization, flexible shape and easy to adjust the voltage division ratio. These characteristics indicate that the sensor has good voltage measurement and sensor network potential.
REVIEW | doi:10.20944/preprints202211.0048.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: electrical systems; power compensation techniques; multistage capacitor banks; power quality; power system safety; mines electrical power supply
Online: 2 November 2022 (06:22:34 CET)
Power quality problem is a hot area in power systems and drives that has drawn the attention of many researchers. This is because of the threat it poses on the health of electrical systems and the cost incurred on utility bills. The problem arises as a result of the need for reactive power to be supplied alongside active power in power transmission and distribution. Unfortunately, reactive power is consumed by almost all components of the system, leading to a shortage. To solve this problem, there is a need to compensate for the lost reactive power. Several researchers have proposed various approaches to mitigate this problem such as thyristor switched capacitor bank, series compensator, series reactor, series var compensator (SVC), Static Synchronous Compensator (STATCOM), synchronous condenser and others. In order to further draw attention in this area, this work investigates a number of research papers on power compensation techniques and draw up challenges from each work that can be considered for further investigation. To this end, each research paper reviewed is evaluated in terms of problem solved, technique used, and results obtained. It therefore offers ample opportunities for researchers to explore in improving power quality and power system safety.
ARTICLE | doi:10.20944/preprints201811.0636.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: new superconductivity, condensation state, new electric field, current emission, new type capacitor, Aharonov–Bohm effect, new energy source
Online: 30 November 2018 (15:57:10 CET)
We previously reported new superconductivity produced by an electrostatic field and a diffusion current in a semiconductor without refrigeration. In particular, the superconductivity was investigated theoretically and confirmed experimentally. Here, we determine that the derived superconducting quantum state can be reproduced in a capacitor. When circuits are formed with this new-type capacitor and diodes, a magnetic field is applied to the diodes’ depletion layer. The depletion layer is biased because of the conversion from the magnetic-field energy to electric-field energy, resulting in the diodes’ spontaneously emitting a current. Thus, the new-type capacitor is charged using no other energy source. This new phenomenon is described theoretically with assistance of initial experiments.
ARTICLE | doi:10.20944/preprints202106.0409.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: DC-link current; harmonic mitigation; voltage source inverters; multi-converter systems; carrier wave interleaving scheme; DC-grid; phase-shifting; capacitor current ripple; unipolar sinusoidal pulse width modulation
Online: 15 June 2021 (14:26:57 CEST)
DC-connected parallel inverter systems are gaining popularity in industrial applications. However, such parallel systems generate excess current ripple (harmonics) at the DC-link due to harmonic interactions between the inverters in addition to the harmonics from the PWM switching. These DC-link harmonics cause the failure of fragile components such as DC-link capacitors. This paper proposes an interleaving scheme to minimize the current harmonics induced in the DC-link of such a system. The results show that when the carrier waves of the two inverters are phase-shifted by 90° angle, the maximum high-frequency harmonic ripple cancellation occurs, which reduces the overall RMS value of the DC-capacitor current.The outcome of this proposed solution is a cost-effective DC-harmonics mitigating strategy for the industrial designers to practically configuring multi-inverter systems, even when most of the drives are not operating at rated power levels. Experimental and simulation results presented in this paper verify the effectiveness of the proposed carrier-based phase-shifting scheme for two different configurations of common DC connected multi-converter systems.