Low DC Research Articles

Local adaptive insulation in amorphous powder cores with low core loss and high DC bias via ultrasonic rheomolding

Amorphous powder cores are promising components for next-generation power electronics. However, they present inherent challenges of internal air gaps and stresses during cold compaction, which significantly deteriorate soft magnetic properties. Here, we report the formation of a local adaptive insulation structure of biconcave lens in amorphous powder cores by ultrasonic rheomolding. Consequently, compared with conventional cold-compacted powder cores, the ultrasonic rheomolded powder cores offer significant simultaneous improvements in the permeability from 31.3–32.4 to 41.8–43.3 and the direct-current bias performance from 69.4–69.7% to 87.4–87.8% (7960 A/m), thereby overcoming the trade-off between permeability and direct-current bias performance. In particular, their core losses are as low as 13.73–15.45 kW/m3, approximately one twentieth of that of the cold-compacted powder cores (282.84–304.03 kW/m3) at a magnetic field of 100 mT and 100 kHz. The biconcave-lens insulation structure can effectively buffer the impact of high mechanical stress on the magnetization of magnetic powder particles, allowing for the ultrasonic rheomolded powder cores to maintain better magnetization efficiency and consequently resulting in excellent soft magnetic properties under the cooperative effect of very low internal stresses and low porosity. The ultrasonic rheomolded powder cores can be used as alternative core components in next generation miniaturized power electronics.

Al2O3 Nanoparticles Infiltered in the Fifth-Generation Adhesive to Carious Dentin. A SEM, EDX, μTBS, and FTIR Assessment

Aluminum trioxide (Al2O3) nanoparticles (NPs) loaded in a fifth-generation adhesive to caries-affected dentin. Molars with occlusal caries were selected. Specimens underwent acid etching and were categorized into 4 groups based on the concentration of Al2O3 NPs in the fifth-generation adhesive. Group 1: 0% Al2O3 NPs, Group 2: 2% Al2O3 NPs, Group 3: 5% Al2O3 NPs and Group 4: 10% Al2O3 NPs. Surface characterization of Al2O3 NPs was assessed via SEM, elemental distribution of particles in Al2O3 was evaluated via EDX, DC was assessed via FTIR, and antimicrobial efficacy was evaluated through the pour plate method. Teeth underwent μTBS testing using the universal testing machine. The Kruskal-Wallis test was used to assess the difference in survival rates of S. mutans. The means of different groups were compared using ANOVA and Tukey’s posthoc test to ascertain significant differences. The highest DC was observed in unmodified adhesive. The lowest DC was displayed in group 4. The highest μTBS scores were observed in group 3 samples. The lowest μTBS was observed in group 1 samples. The most effective group against S. mutans was 4. The ER adhesive loaded with 2 wt% and 5 wt% Al2O3 NPs exhibited superior μTBS and antibacterial effectiveness. The addition of Al2O3 to the adhesive resulted in a reduction in the degree of conversion.

A Novel Fast Contact Operating Mechanism of the Medium and Low Voltage Hybrid DC Current Limiting Circuit Breaker

In order to solve the problem of the slow initial speed caused by the large mass of the bistable permanent magnetic actuator (PMA) in the traditional bistable permanent magnetic–electromagnetic repulsion mechanism (PM-ERM), a novel fast contact operating mechanism is proposed by using the flexible spring system (SS) between the PMA and the ERM. The novel structure can separate the mass of the PMA and the ERM at the initial phase of the interrupting process, improve the initial speed of the contact and increase the initial opening distance of the contact. Firstly, the paper conducts an extensive investigation and analysis of the principle of the existing fast operating mechanism and points out the advantages and disadvantages of the existing mechanism. In order to meet the requirement of fast interrupting and improve the service life of the mechanism, a novel mechanism is proposed. And then, the working principle of the novel mechanism is introduced. The cooperative relationship between the ERM and the PMA and the working principle and performance parameter requirements of the ERM, SS and PMA are analyzed and designed. Finally, the feasibility of the novel mechanism is verified by the experiment. The results show that the opening distance of the novel operating mechanism can reach 2.25 mm in 1 ms. Compared with 1.24 mm of the traditional operating mechanism, it improves the initial opening distance of the contact by 81.5% and is conducive to the rapid interruption of the Hybrid DC current-limiting circuit breaker (HDCCLCB).

Low Voltage DC Solid-State Circuit Breaker With Soft Turn-Off and Self-Charging Operation

Low Voltage DC Solid-State Circuit Breaker With Soft Turn-Off and Self-Charging Operation

An optical atomic clock using 4DJ states of rubidium

Abstract We analyze an optical atomic clock using two-photon 5 S 1 / 2 → 4 D J transitions in rubidium. Four one- and two-color excitation schemes to probe the 4 D 3 / 2 and 4 D 5 / 2 fine-structure states are considered in detail. We compare key characteristics of Rb 4 D J and 5 D 5 / 2 two-photon clocks. The 4 D J clock features a high signal-to-noise ratio due to two-photon decay at favorable wavelengths, low dc electric and magnetic susceptibilities, and minimal black-body shifts. Ac Stark shifts from the clock interrogation lasers are compensated by two-color Rabi-frequency matching. We identify a ‘magic’ wavelength near 1060 nm, which allows for in-trap, Doppler-free clock-transition interrogation with lattice-trapped cold atoms. From our analysis of clock statistics and systematics, we project a quantum-noise-limited relative clock stability at the 10 − 13 / τ ( s ) -level, with integration time τ in seconds, and a relative accuracy of ∼ 10 − 13 . We describe a potential architecture for implementing the proposed clock using a single telecom clock laser at 1550 nm, which is conducive to optical communication and long-distance clock comparisons. Our work could be of interest in efforts to realize small and portable Rb clocks and in high-precision measurements of atomic properties of Rb 4 D J -states.

Analysis of Electromagnetic Buffer Characteristics of DC Fast Vacuum Switch

In order to solve the contradiction between the rapid isolation of low voltage DC faults and the low bounce of small stroke vacuum switches, taking the fast vacuum switch for 400 V DC power distribution system as the research object, the electromagnetic buffer simulation and experimental research in the opening process are carried out. The influencing factors of the dynamic and reaction mechanism and buffer output characteristics are analyzed, and the electromagnetic buffering effect under typical working conditions is simulated, which proves that electromagnetic buffer is a necessary part of 400 V fast vacuum switch and the motion characteristics of fast switching are optimal when applying 220 V electromagnetic buffer. According to the simulation calculation results, the engineering prototype was made, the experimental research on the electromagnetic buffer under typical working conditions was carried out, and the design criteria of the small stroke electromagnetic buffer were proposed, which solved the problem of fast switching of small stroke and reliable control and low bounce. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

A novel memristive chaotic jerk circuit and its microcontroller-based sliding mode control

Due to the experimental realization of memristor circuit elements, research on memristors and memristor-based circuits has surged. Because of their nonvolatile and nonlinear behavior, memristors can be easily applied to chaotic circuits. This study introduces a novel memristive 3D chaotic jerk system, comprising only seven terms, along with its electronic model and microcontroller-based control. The flux-controlled memristor-based jerk system exhibits complex dynamics, which were analyzed through various properties such as phase portraits, the Jacobian matrix, equilibria, eigenvalues, Lyapunov spectra, bifurcation diagrams, and transient chaos behavior. Three controllers, namely, nonlinear feedback, classical sliding mode, and integral sliding mode were designed to control the chaotic jerk oscillator. Lyapunov functions were used to synthesize the nonlinear feedback controller and ensure system stability with the sliding mode technique. Numerical tests under various performance criteria and disturbance conditions showed that the sliding mode controller outperforms the nonlinear feedback controller due to its single-state control structure. The chaotic jerk oscillator hardware circuit was designed and implemented, operating easily with initial conditions set to zero and low DC supply voltages, with all output voltages within ±6V. Both theoretical and simulation results demonstrate the system’s complexity and applicability, with experimental results aligning well with simulations. Consequently, effective microcontroller-based control was achieved using a single-state controller.

A new modulation for three‐phase current source converter

AbstractThis brief proposes an improved pulse width modulation (PWM) scheme, which uses diode voltage clamping characteristics to achieve the direct control of three‐phase current source converter without any logical transformation. Compared with the traditional indirect carrier modulation scheme—mapping‐PWM, the proposed scheme can solve the disadvantages of low DC current utilization, high switching loss, and complex control process. The generation mechanism of IPWM is analyzed in this brief. Then, based on the generation mechanism, the output characteristics of the system under IPWM are analyzed and compared with the traditional modulation scheme. Finally, the experimental results verify the effectiveness the proposed modulation scheme.

Investigations into optimum non‐periodic bursts scheme in radar pulse train designed for fixed‐wing drone detections by multi‐function radar

AbstractDrone surveillance with multi‐function radar (MFR) can benefit a lot from the careful radar pulse train organisation into dedicated sub‐RPTs serving particular needs of tasks. In contemporary scenarios of MFR applications, where navigation, search and rescue, and natural environment safeguarding are to be shared, of particular importance is a case where airborne small drone detection radar performs other tasks concurrently. Resource sharing within the radar unit is based on variables and unpredictable circumstances, leading to strains in resources in MFR. Consequently, such constraints limit MFR functioning with optimal drone sensitivity for its own sake. To ensure a high quality of radar services performed quickly, with a low DC power consumption, the task sharing approach by the common MFR platform, non‐periodic bursts emission of radar pulse energy has gained our major attention. At the same time, it was assumed that bursts feature periodic time intervals between radar pulses, which is a favourable circumstance in the control and implementation of signal processing. Each sub‐RPTs is designed to cope with particular detection tasks. One to four linear polarisations (VV, VH, HV, HH) are activated. The focus of the investigation was on the radar emitting a few thousand pulses per second, but only a few 10 pulses per second were expected to be required to detect small airborne drones. The core of the research study was the optimisation process of the scheme operating with 4 to 16 pulse bursts optimised for drone detection with a modest use of resources at MFR. While performing several activities, the X‐band MFR platform called ENAVI was developed in‐house. The proposed non‐periodic burst scheme optimisation approach was validated with in‐field tests with the ENAVI radar model. The in‐air target was a 3‐metre fixed‐wing drone having low RCS and flying at different altitudes with a speed close to 200 km/h. The radar antenna was a 26 dBi low‐profile dual‐polarisation array making it feasible to detect drones remaining a few degrees off the antenna breadboard direction. A very high likelihood of detection of drones from a few kilometres distance was demonstrated within one second. The authors present the effectiveness of the cell‐averaging technique which proved to correctly detect drones within a 7‐km range, and how MFR radar echoes can be used for basic weather surveillance. One vertical VV polarisation was used for drone detection and two VV and VH polarisations for weather observation. Weather radar capabilities were examined against heavy rain clouds imposing a hazard to the safety of drone flights.

Active elimination of DC bias current of a SiC based dual active bridge by controlling the dead time period

AbstractDual active bridge (DAB) is an isolated DC‐DC converter gaining wider attention in power electronics applications. The high frequency (HF) transformer is an integral part of the DAB which is prone to saturation. Silicon carbide (SiC) based DAB are generally preferred for highly efficient power conversions, calling for an extremely low DC resistance of the transformer. This aggravates the DC bias issue significantly. The DC bias current generally flows due to the mismatch in static and transient switching of active devices, leading to eventual saturation of the transformer. This paper proposes an active method to precisely control the dead time of the devices (8–100 ns) without sacrificing the voltage utilization of the converter. This method does not require a sophisticated DC offset current measurement technique. The field programmable gate array (FPGA) based control platform on the gate driver side executes the proposed algorithm. The proposed control is experimentally verified in a 5 kW SiC based converter. The control implementation methodology is discussed with the support of necessary experimental results.

A new fault detection and relay coordination technique for low voltage DC microgrid

Integration of various distributed generation units in the DC distribution network creates an outsized impact on magnitude and direction of fault current. The specific behaviour of fault current during a short circuit fault demands quick and reliable detection and isolation of fault, which poses a significant challenge in developing an effective protection and coordination scheme for DC microgrids. In this regard, a new fault detection and relay coordination algorithm is proposed for a Low voltage DC (LVDC) microgrid, which utilizes inverse time relay characteristics based on variance of fault current. While the relay responds and picks up during both internal and external faults, its operation is automatically limited upon operation of the downstream circuit breaker without the need for any communication channel. The efficacy of the proposed strategy is evaluated by modelling a mesh-connected DC microgrid network using PSCAD/EMTDC software. The protection coordination problem is developed as a constraint non-linear optimization problem to determine optimal relay settings. The proposed approach has been tested by simulating various types of faults at different fault locations and fault resistances along with various microgrid operating modes. The results suggest that the proposed strategy stands out by optimizing relay operating time and providing backup protection while upholding relay coordination. A comparative assessment of the proposed technique with existing ones proves its effectiveness in terms of swift relay tripping time, better immunity against noise, and independency against microgrid operating mode and topology.

Dual input single Output quadratic Boost converter for DC microgrid

DC-DC converters play a critical role in various applications, including DC microgrids, electrical vehicles, data centres and aerospace power systems. This article provides a description of a non-isolated Dual Input Single Output Quadratic Boost DC-DC Converter (DISOQBC) designed for DC microgrids. PV module and battery are low dc voltage power generators. DC microgrid requires high voltage for its operation effectively. By utilizing the proposed converter, the PV module and battery are integrated with separate sources. Achieving a high efficiency and voltage conversion ratio, the proposed converter is distinguished by low components used. The operation of the converter, component design, steady state analysis, and small-signal model has been reported. The proposed converter's benefits include the converter's ability to handle more than one source, deliver more gain than the conventional converter, simple control and reduced losses. The outcome of simulating the converter validates the proposed converter's theoretical operation. The laboratory prototype is ultimately employed to validate and verify the performance of the proposed DISOQBC.

The stability of phycocyanin extracted from Arthrospira platensis against osmotic, acid, and temperature stress conditions

The main problem of using natural blue pigment of phycocyanin produced by Arthrospira platensis (spirulina) is its instability in the food matrix because of environmental stress. This study aimed to investigate the stability of phycocyanin under simulated conditions in food formulations against osmotic, acid, and temperature stress conditions. Thermal degradation constant (Dc) and half-life (t½) of phycocyanin extracted from Arthrospira platensis were analyzed using response surface methodology followed by a first-order kinetic reaction. The stability of phycocyanin was assessed under various temperature (50–98ºC), NaCl (0–2% w/w), and pH (4–7) values. Results showed that the stability of phycocyanin extracted from Arthrospira platensis is high at neutral pH and concentration of 1% (w/w) NaCl. The stability decreased with increase in temperature at ≥75°C. The highest stability of phycocyanin (the lowest Dc and the maximum t½ were 0.011 min-1 and 54.03 min, respectively) was achieved at 66.89°C, pH = 6.6, and NaCl of 0.40% w/w. According to processing conditions, content of phycocyanin required for a food matrix is successfully calculated by the response surface method. This research showed that phycocyanin is stable at thermal shock in a neutral pH medium and low content of NaCl (0.40% w/w).

Design and prototyping of miniature wind turbine and power generation section for the exploitation of wind generated by vehicle movement in road tunnels

A strong development of renewable energy is envisioned in order to achieve targets of reduction for greenhouse emissions. In particular, small scale systems for distributed renewable energy production can be very useful to this purpose in urban areas where the generated power can be directly used.In this context, the present paper concerns the aerodynamic and electromechanical design of a small wind turbine for the exploitation of the wind generated by vehicles movement in road tunnels. The generated energy is directly used to power road delineators, usually equipped with LED technology and, therefore, characterized by low energy requirements, DC supply and long life.The first part of the study addressed the definition of the operating conditions of the wind turbine inside road tunnel. Then, the aerodynamic design of the turbine was conducted through CFD simulations maximizing the efficiency with reduced size and cost. The power generation section is chosen and coupled to the turbine for integrated system prototyping. Simulation results prove that power generated by a single wind turbine is suitable to supply 10 delineators maximum, covering about 100 m of tunnel. Moreover, wind turbine performance is also validated through test on a real scale prototype of the complete device.

Carrier-Gas free arc igniter microplasma optical emission spectrometry for the determination of arsenic in soil

Rapid on-site assessment of arsenic contamination in soils is crucial for environmental protection and human health. In order to build an effective and affordable device for the determination of arsenic, the use of carrier gas supplies and high power energy consumption largely limit the miniaturization of microplasma-based optical emission spectrometry (OES). An arc igniter microplasma (AIM) can be powered by a low DC power supply and operated in the atmosphere of air without gas infusion, which is beneficial to construct a carrier-gas free and low power supply setup. Hydride generation (HG) can improve sample transport efficiency and reduce matrix effects, but the generated by-product hydrogen has not been explored as a sole working gas for plasma excitation. In this work, a hydride generation arc igniter microplasma optical emission spectrometer (HG-AIM-OES) was fabricated for detecting arsenic in soils. H2 derived from HG was served as a working gas to transport AsH3 to excite, eliminating the use of a carrier gas unit. Under the optimized operating conditions, the limit of detection (LOD) for arsenic was 164 μg/L (the analytical line at 234.98 nm), and good linearity of the method was achieved in the range of 0.5–20 mg/L with a precision of 3.14 % (the concentration of arsenic at 1 mg/L). In addition, the influence of H2 on AIM physical properties was carefully studied in the air and Ar discharge atmospheres. The accuracy of the proposed device was validated by the analysis of certified reference materials (CRMs) and a real soil sample, resulting in good agreement with the obtained results by air and Ar as working gas. This HG-AIM-OES system provides a miniaturized, carrier gas-free and low power consuming tool for monitoring and assessment of arsenic-contaminated soils.

A 30-60 GHz Broadband Low LO-Drive Down-Conversion Mixer with Active IF Balun in 65 nm CMOS Technology.

A 30~60 GHz broadband down-conversion mixer driven by low local oscillator (LO) power is presented. The down-conversion mixer utilizes an input signal coupling technique based on the Marchand balun to achieve broadband operation and achieves low LO power drive and low DC power consumption through the use of a weak inversion bias with Gilbert switching devices. The broadband conversion of single-ended to differential signals is achieved using the Marchand balun with compensation lines, and an equivalent circuit analysis is performed. For the intermediate frequency (IF) output, a self-biased IF trans-impedance amplifier with current reusing and an active IF balun structure are used to achieve signal amplification and single-ended signal output. Test results show that the proposed mixer achieves a conversion gain of -1.2 to 6.4 dB in an IF output bandwidth of 0.1 to 5 GHz at radio frequency (RF) input frequencies of 30 to 60 GHz and LO driving power of -10 dBm. The DC power consumption of the core mixing unit of the proposed mixer is 4.8 mW, and the DC power consumption including the IF amplifier is 28.3 mW. The proposed mixer uses a 65 nm CMOS technology with a chip area of 0.26 mm2.

Fabrication of rGO-decorated hBNNS hybrid nanocomposite via organic-inorganic interfacial chemistry for enhanced electrocatalytic detection of carcinoembryonic antigen.

Organic-inorganic hybrid nanocomposites (OIHN), with tailored surface chemistry, offer ultra-sensitive architecture capable of detecting ultra-low concentrations of target analytes with precision. In the present work, a novel nano-biosensor was fabricated, acquainting dynamic synergy of reduced graphene oxide (rGO) decorated hexagonal boron nitride nanosheets (hBNNS) for detection of carcinoembryonic antigen (CEA). Extensive spectroscopic and microscopic analyses confirmed the successful hydrothermal synthesis of cross-linked rGO-hBNNS nanocomposite. Uniform micro-electrodes of rGO-hBNNS onto pre-hydrolyzed ITO were obtained via electrophoretic deposition (EPD) technique at low DC potential (15V). Optimization of antibody incubation time, pH of supporting electrolyte, and immunoelectrode preparation was thoroughly investigated to enhance nano-biosensing efficacy. rGO-modified hBNNS demonstrated 29% boost in electrochemical performance over bare hBNNS, signifying remarkable electro-catalytic activity of nano-biosensor. The presence of multifunctional groups on the interface facilitated stable crosslinking chemistry, increased immobilization density, and enabled site-specific anchoring of Anti-CEA, resulting in improved binding affinity. The nano-biosensor demonstrated a remarkably low limit of detection of 5.47pg/mL (R2 = 0.99963), indicating exceptional sensitivity and accuracy in detecting CEA concentrations from 0 to 50ng/mL. The clinical evaluation confirmed its exceptional shelf life, minimal cross-reactivity, and robust recovery rates in human serum samples, thereby unraveling the potential for early, highly sensitive, and reliable CEA detection.

An advanced graph algorithm-based protection strategy for detecting kilometric and cross-country faults in DC microgrid

Low voltage DC microgrids (LVDC) are on rise, because of increase in usage of electronics-based utility loads. However, the protection and safety aspects of these grids remain unresolved due to the fault current magnitude, unnecessary tripping, and blinding of protection. In this paper, an adaptive differential protection system incorporated with an advanced graph algorithm is proposed for DC microgrid. This graph algorithm is a combination of Fenwick tree and Bidirectional Dijkstra algorithm. Fenwick tree algorithm is used to determine the network configuration and Bidirectional Dijkstra algorithm is used to determine the least distance from the fault location to the nearest distributed generations. The developed protection scheme is applied to a 7 bus, 400 V DC microgrid setup using Real Time simulator (control hardware in loop) to detect and clear the faults such as kilometric faults, and cross-country faults. In terms of efficiency, the proposed algorithm demonstrates superiority over the conventional algorithm by detecting and rectifying faults in 384 μs.The results depict the robustness of the protection setup in clearing the faults rapidly with minimum network disconnection.

BLDC Motor based Air Dessert Cooler

Abstract: This paper proposes a new position sensorless drive for brushless DC (BLDC) motors.Growing need for high productivity is placing new demands on mechanisms connected with electrical motors. The demand for low costBrushless DC (BLDC) motor has increased in industrial applications. A simple BLDC motor control algorithm forlow cost motor drive applications using general purpose microcontrollers has been created and presented in this paper. Proposed design will allow the user to rotate the motor either clockwise or counter clockwise direction. Dependingon the rotor position the sensor will give response to the controller circuit. Then the controller circuit will fix the direction of current following to the stator. The design controller circuit is also implemented. The overall design consists of microcontroller circuit, logic gates, switching devices (MOSFET/BJT), BLDC motor, sensors.

Underground Cable Fault Detection Using IOT

Abstract: The objective of this project is to determine the distance of underground cable fault from base station in kilo meters using an Arduino. The underground cable system is a common practice followed in many urban areas. An issue may happen in an underground cable just because of earth tremors or any burrowing procedure. Since the area of the issue happened is obscure it is very hard for the fixing procedure. This hindrance is handled with the assistance of optical fibre framework. A lot of optical strands is put alongside the force cables. While a fault occurs for some reason, at that time the repairing process related to that particular cable is difficult due to not knowing the exact location of the cable fault. The proposed system is to find the exact location of the fault. The project uses the standard concept of Ohms law i.e., when a low DC voltage is applied at the feeder end through a series resistor (Cable lines), then current would vary depending upon the location of fault in the cable. In case there is a short circuit (Line to Ground), the voltage across series resistors changes accordingly, which is then fed to inbuilt ADC of Arduino to develop precise digital data for display in kilometres. The project is assembled with a set of resistors representing the cable length in km and the fault creation is made by a set of switches at every known km to cross check the accuracy of the same. The fault occurring at a particular distance, the respective phase along with the distance is displayed on the LCD. The same information is also sent over IOT, interfaced to the Arduino. Further this project can be enhanced by using capacitor in an ac circuit to measure the impedance which can even locate the open circuited cable, unlike the short circuited fault only using resistors in DC circuit as followed in the above proposed project.