Moderate Duty Ratio Research Articles

High power voltage multiplier (VM) PFC Converter with inherent ZCS Characteristics and high step-ip gain for enhanced low-line efficiency

In this paper, a Voltage Multiplier (VM) converter configuration has been designed for high Power PFC application, ensuring reduced losses and high system efficiency.The conventional PFC system is improved with adding VM circuit configuration that enhances the static gain features with moderate duty ratio (D), and hence, the reverse recovery (RR) issue is resolved. The VM section inherently adds two main specific features of clamping behavior and ZCS phenomenon to the PFC system. An experimental prototype of 2 kW, 600 V VM PFC converter configuration is designed and its effectiveness is validated under low line input of 100 V , operating at a high duty ratio, D = 0:67. The Real-Time Interface (RTI) feature of dSPACE1104 and MATLAB/Simulink are used to give the control signal for the verification of the system. Always, less than half of the output voltage (300 V ) appears across the switches of the converter, hence, voltage stress of the switch is minimized. Also, ZCS phenomenon is evident during switching commutations due to the snubber circuit behavior of the resonant tank, included in the proposed PFC converter. Hence, the overall system efficiency is improved. Furthermore, higher system efficiency is maintained for different rating which has been tested in this research work.

Dual-Switch Enhanced Gain Boost DC–DC Converters

A switching capacitor-based boost converter topological evolution is proposed in this article. Switching capacitor with dual-switch configuration is the basis for the topological evolution with common ground feature. The topologies evolved are capable of yielding high-voltage transformation ratio at smaller duty ratios like in Z-source dc–dc converter topologies. The front-end structure provides a voltage gain of 1/(1 − 2D) while the upstream circuit structure is compatible for embedding the voltage multiplier cells and thus gain enhancement becomes an easier task. On this basis, four different enhanced gain boost topologies with common ground feature [dual-switch-based switching-capacitor converter (DSSCC) Type-1 and -2, and dual-switch-based switching-capacitor fourth-order converter (DSSCFO) Type-1 and -2] are introduced in this article. In all these topologies, a small adjustment in the duty cycle is sufficient enough to ensure load voltage regulation even if the input supply voltage varies over wide ranges. Among these four proposed topologies, DSSCC Type-1 and DSSCFO Type-2 exhibit low source current ripple content due to the presence of inductance at the source side. Of these two, DSSCFO Type-2 exhibits low source current ripples as well as high voltage gain at moderate duty ratios. In view of this, detailed analysis and experimental investigations are established for DSSCFO Type-2. A comprehensive comparison of the proposed topologies with other reported topologies is given, wherein they exhibit identical as well as closely following voltage gain. A 220 V, 120 W, 50 kHz prototype is constructed for performance verification. Measurement results are provided to demonstrate the enhanced gain boosting along with low source current ripple features.

Steady-State Performance Characteristics of a DC Motor fed by Quadratic DC-DC Boost Converter

This paper presents the analysis of steady-state performance of a DC motor fed by a non-isolated quadratic DC-DC boost converter. The proposed quadratic configuration based non-isolated high voltage gain DC-DC converter operating in continuous conduction mode employs one power switch and reduced number of diodes and passive components. Due to single power switch, the switching and conduction losses are reduced thereby improving the converter efficiency. A DC shunt motor of 5 HP power rating is used as load to the proposed converter. The proposed cost-effective converter-fed DC motor operating under no-load is simulated using MATLAB / SIMULINK tool. The steady-state performance characteristics, such as speed, torque, and armature current of the DC motor, are obtained for one particular value of duty ratio of the power switch. The results validate the superior performance of the suggested DC-DC converter-fed DC motor at moderate duty ratio.

The ATPase mechanism of myosin 15, the molecular motor mutated in DFNB3 human deafness

Cochlear hair cells each possess an exquisite bundle of actin-based stereocilia that detect sound. Unconventional myosin 15 (MYO15) traffics and delivers critical molecules required for stereocilia development and thus is essential for building the mechanosensory hair bundle. Mutations in the human MYO15A gene interfere with stereocilia trafficking and cause hereditary hearing loss, DFNB3, but the impact of these mutations is not known, as MYO15 itself is poorly characterized. To learn more, we performed a kinetic study of the ATPase motor domain to characterize its mechanochemical cycle. Using the baculovirus–Sf9 system, we purified a recombinant minimal motor domain (S1) by coexpressing the mouse MYO15 ATPase, essential and regulatory light chains that bind its IQ domains, and UNC45 and HSP90A chaperones required for correct folding of the ATPase. MYO15 purified with either UNC45A or UNC45B coexpression had similar ATPase activities (kcat = ∼ 6 s−1 at 20 °C). Using stopped-flow and quenched-flow transient kinetic analyses, we measured the major rate constants describing the ATPase cycle, including ATP, ADP, and actin binding; hydrolysis; and phosphate release. Actin-attached ADP release was the slowest measured transition (∼12 s−1 at 20 °C), although this did not rate-limit the ATPase cycle. The kinetic analysis shows the MYO15 motor domain has a moderate duty ratio (∼0.5) and weak thermodynamic coupling between ADP and actin binding. These findings are consistent with MYO15 being kinetically adapted for processive motility when oligomerized. Our kinetic characterization enables future studies into how deafness-causing mutations affect MYO15 and disrupt stereocilia trafficking necessary for hearing.

A novel tooling approach for micro electrical discharge machining of micro-slits on Inconel 600 using foil tools

ABSTRACT Inconel 600 is widely used in various engineering applications including aerospace, chemical and food processing industries. Traditional machining of Inconel 600 is difficult due to high tool wear, cutting forces, temperature, surface roughness and dimensional inaccuracy. The present article describes research work involved in micro-EDM of Inconel 600 to investigate material removal rate, tool wear rate and dimensional overcut. Major process parameters, namely, voltage, duty ratio and sensitivity are considered. Response surface methodology is used to design the experiments. A novel tooling approach, i.e. copper foil tool is proposed in the present study for machining of micro-slits on the workpiece. It is observed that material removal increases with an increase in voltage, optimum duty ratio and sensitivity. Tool wear decreases with a decrease in voltage, moderate duty ratio and sensitivity. A mathematical model is developed for predicting the material removal rate on the basis of experimental results. Multi-objective optimisation is performed by using Grey relational analysis. A confirmation experiment validates the improvement in responses under optimised values of process parameters. It is observed that the use of foil tool improves material removal and dimensional accuracy of the workpiece. A novel foil tooling approach is helpful in the machining of complex microfeatures with high material removal rate and dimensional accuracy.

Soft-Switched Interleaved DC/DC Converter as Front-End of Multi-Inverter Structure for Micro Grid Applications

An isolated four channel dc/dc converter with zero voltage switching is proposed as the front-end of multiple inverter structures to integrate renewable and other low voltage energy sources to micro grids. The interleaving technique is adopted to connect each module of proposed converter to a common dc source. This dc source can be a fuel cell stack, PV panels, battery, or any other low voltage dc source. All four channels are interleaved and a phase shift of 90° is provided between the gate signals of each channels, which reduces the input current ripple. The output port of the proposed converter provide four isolated and regulated dc voltages. These isolated dc sources can be connected in series or parallel or series-parallel manner to obtain required dc-link voltage of various inverter structure. Issues like capacitor voltage balancing of diode clamped multilevel inverters can overcome through the proposed converter. By incorporating a coupled inductor for isolation and energy storage along with voltage multiplier circuit, the proposed converter can achieve higher voltage step up with lower turns ratio and lower voltage stress at moderate duty ratio. Hence, mosfets of low voltage rating (low R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> (ON)) can be utilized to reduce conduction loss. A 2 kW prototype of the proposed interleaved dc/dc converter is developed and tested with diode clamped three-level inverter, five-level inverter, and three-phase two-level inverter to verify the design.

Modeling of high step-up converter in closed loop for renewable energy applications

A majority of small-scale renewable energy sources including the solar PV modules, fuel cells gives out output voltage in the range of around 15–40 V DC. This needs to be stepped up to suit load requirements using a high voltage gain converter. Since renewable sources inherently generate sudden variations in input voltage, a good output voltage profile even during such random variations in input conditions is essential. This paper presents modeling of a high step-up converter configuration with closed loop control. The converter topology is designed to operate with moderate duty ratios and the simple coupled inductor. The converter is capable of high step-up and can find application in solar PV systems. The controller response is good with low steady state error and required dynamics. The modeling and simulation is carried out using MATLAB/Simulink software package.

A Novel Transformer-less Interleaved Four-Phase Step-Down DC Converter With Low Switch Voltage Stress and Automatic Uniform Current-Sharing Characteristics

In this paper, we propose a novel transformer-less direct current (dc) converter that features low switch voltage stress and automatic uniform current sharing. An interleaved four-phase voltage divider operating from a 400 V dc bus is used to achieve a high step-down conversion ratio with a moderate duty ratio. Based on the capacitive voltage division, the proposed converter achieves two major objectives, i.e., increased voltage conversion ratio, due to energy storage in the blocking capacitors, and reduced voltage stress of active switches and diodes. As a result, the proposed converter permits the use of lower voltage rating MOSFETs to reduce both switching and conduction losses, thereby improving the overall efficiency. In addition, due to the charge balance of the capacitors, the proposed converter enables automatic uniform current sharing of the interleaved phases without adding extra circuitry or complex control methods. The operation principles and performance analyses of the proposed converter are presented, and its effectiveness is verified by a 500 W output power prototype circuit that converts 400 V input voltage into 24 V output voltage.

HIGH GAIN DC-DC CONVERTER WITH LOAD REGULATION

High gain dc-dc converters are gaining importance due to the latest trends in extracting power from renewable energies. The most commonly available renewable energy resources are wind and solar. The voltage developed while tapping energy from these sources are very low. Often the load requires larger than the voltage developed by the renewable sources which necessitates a high gain DC-DC converter with moderate duty ratio. Conventional boost converter cannot achieve ultra high voltage gain at moderate duty ratio. The aim of designing engineers is to obtain converters with high gain with moderate duty ratio, reduced switch stress, and cost. Here a single switch non isolated dc-dc converter with capacitor-diode voltage multiplier topology is presented. A 30W prototype of the converter is designed and closed loop simulation is conducted to explain the effectiveness of the controller at different load condition to obtain regulated output.

Driving Characteristics of a Traveling Wave-Type Ultrasonic Motor with Three State PWM Control Adding a Standing Wave in Its Stator

An ultrasonic motor (USM) can produce a “free state” where the frictional force between the rotor and the stator diminishes when a standing wave is excited in the USM instead of a traveling wave. In this paper we propose a three state PWM drive method in which the duty ratios of a traveling wave, a standing wave and a switch-off period are changed in order to control the motion of the USM. It was confirmed that a hysteresis of torque curve for the duty ratio of the traveling wave was reduced by introducing a standing wave to the stator. If the duty ratio of the standing wave is small, the large torque due to a self-locking characteristic is obtained even at the small duty ratio of a traveling wave. When the standing wave ratio is increased, the relationship between the duty ratio of a traveling wave and the output torque of an USM becomes approximately linear. This linearity is optimum at the moderate duty ratio of a standing wave with a short switch-off period.