Variation Of Voltage Amplitude Research Articles

ЗМЕНШЕННЯ ВПЛИВУ ВІДХИЛЕНЬ ПАРАМЕТРІВ ГЕНЕРАТОРІВ У ПРЕЦИЗІЙНИХ КВАДРАТУРНИХ МОСТАХ

The article is devoted to solving the problem of attestation of electric capacity standards at industrial frequency. The expediency of using a quadrature bridge of alternating current to determine the parameters of standards of electric capacity at industrial frequency by comparison with the parameters of standards of active resistance was noted. The advantage of using a bridge imbalance indicator with high input impedance is shown, which consists in the possibility of reducing the influence of higher harmonics of the supply voltages. An analysis of the well-known method of reducing of measurement errors caused by the deviation of the generator parameters from the calculated ones was carried out. It is shown that the known method does not provide sufficient compensation for the influence of these errors when the deviations of the generator parameters increase, as well as when the deviations of the bridge from the balance state increase. An iterative algorithm for calculating the measured deviation of the impedance ratio of the compared standards from the nominal value is proposed. Mathematical expressions for calculating the measured quantity are given. Calculations of the components of the measurement error for different values of generator voltage deviations were carried out. Calculations were performed for two variants of generator voltage variation implementation: multiplicative voltage amplitude variation and additive voltage phase variation. The developed iterative correction method allows to reduce the specified errors to the required levels in a small number of iteration steps - in the vast majority of cases, two steps are enough. The application of the method allows obtaining high metrological characteristics with rather large deviations of the voltage ratio of bridge generators, which makes it possible to reduce hardware costs when implementing quadrature alternating current bridges for comparing capacitance and active resistance standards. References 15, figure 1, table 1.

Electromyographic signals and the starting threshold voltage of orbicularis oris muscle in healthy rhesus monkeys

Objective: To investigate the characteristics of electromyography (EMG) signals and the starting threshold voltages of the orbicularis oris muscles (OOM) in healthy rhesus monkeys under different muscle movement conditions. Methods: The EMG signals and the starting threshold voltages at different time points in 4 healthy rhesus monkeys were acquired and recorded with EMG device and evoked potentiometer. The voltage amplitude variation of EMG signals was analyzed, and the voltage amplitude range of EMG signals at the beginning of OOM contraction was established. The data were statistically analyzed by one-way ANOVA. Results: The EMG of OOM in healthy monkeys in the quiet, natural and continuous mouth-closed state was linear and relatively stable, and the absolute value fluctuated between 15 and 50 μV. The EMG waveform increased rapidly during the natural lip contraction movement, and its amplitude fluctuated greatly, with the highest absolute value of the peak value reaching hundreds of microvolts. The amplitude of EMG induced by continuous mouth closure was more than thousands of microvolts. There was no significant difference in EMG amplitudes of OOM in the healthy rhesus monkey under quiet and continuous lip closure at different time points (P>0.05). There was no significant difference in threshold voltages in the state of natural lip contraction of bilateral OOM at different time points (average range: 57.17-57.47 μV) in the healthy rhesus monkeys (P>0.05). There was no significant difference in threshold voltages of OOM induced by bilateral OOM at different time points(average range: 55.38-55.99 μV) in the healthy rhesus monkeys(P>0.05). There were significant differences in the absolute values of EMG amplitudes of OOM between the three lip movement modes: (30.67±8.72) μV in quiet and natural continuous lip closure (475.12±54.72) μV in natural lip contraction, and (921.22±312.79) μV in the induced persistent lip closure, with t values of -8.48, -9.35 and -5.01 respectively, all P<0.001. Conclusions: The EMG signals of OOM show different characteristics under different muscle movement conditions, which can be used as a basis for computer to judge and recognize the movement conditions of OOM. The upper limits of the EMG threshold voltage values of OOM under different motion states are 55-60 μV.

Novel method based on Teager Energy Operator for online tracking of power quality disturbances

• A TEO -based PQ disturbance tracking algorithm is proposed for the voltage fluctuations with sag disturbance. • The inverter-based DG, nonlinear load and fault event influence on the voltage flicker and sag levels. • The new approach can be used to track multiple PQ disturbance with a complex structure. • This method with proper accuracy can track the voltage amplitude variations in the presence of notch and harmonics. This paper presents an optimal algorithm for simultaneous tracking of power quality (PQ) events in distribution systems in the presence of the inverter-based distributed generation and nonlinear load. The algorithm is based on Teager Energy Operator (TEO). The main specification of the Teager Energy Operator, compared with the commonly used methods in the literature, is the simplicity of its mathematical. Using a proposed method, a suitable combination of the TEO and a relevant filter set is defined as a criterion to reduce envelope ripples and improve a suitable tracking for the power quality disturbances. This approach is able to accurately detect the distortions and sudden changes of voltage under different conditions. The paper considers the voltage fluctuations and voltage sag at the point of common coupling (PCC) and nearby points of the PCC as these voltage disturbances. Extensive simulations for the several power quality disturbance signals and the distribution network based on nonlinear elements using the new approach are performed and performance evaluation is clearly distinguished from the results. Simulation results for single and multiple power quality disturbances present that the proposed method is precise and suitable in detecting voltage disturbances.

Experimental Investigation and Intelligent Optimization of Airfoil Zero-Lift Drag Reduction with Plasma Actuators

Micro aerial vehicles flying at low speeds are becoming increasingly popular in military and daily life. Nevertheless, the short cruise time related to the poor aerodynamic efficiency of the wing at low Reynolds numbers is still a key issue. To deal with this, a spanwise plasma actuator array is used to reduce the zero-lift drag of a low-Reynolds-number airfoil, and experimental optimization of the electrical parameters is performed with intelligent algorithms. Results show that for efficient drag reduction, an unsteady unidirectional jet working mode should be preferred by the plasma actuator. In this mode, the drag reduction maps are mostly flat, and the drag reduction magnitude is insensitive to the variation of input voltage amplitude. There exists a threshold particle-observed Strouhal number (0.2) below which the drag reduction effectiveness drops sharply. As a comparison, the map of the power saving ratio shows a steep gradient, and its maximum always resides on the lower bound of duty cycle. With increasing freestream velocity, the mean drag reduction decreases monotonically. A genetic algorithm shows superior performance over surrogate-based optimization by reaching a maximum drag reduction of 40% and a peak power saving ratio of 0.7. Particle image velocimetry results reveal that there exists a laminar separation bubble on the airfoil. With plasma actuation, the transition location is shifted upstream, and the separation region is eliminated significantly. At low speeds, this pressure drag reduction exceeds the friction drag increase, resulting in a net drag decrease. However, transition-induced drag variation can only explain part of the total drag reduction, and the rest is inferred to be turbulent friction drag reduction.

Comparison between patient-specific deep brain stimulation simulations and commercial system SureTune3

Objective. Software to visualize estimated volume of tissue activated (VTA) in deep brain stimulation assuming a homogeneous tissue surrounding such as SureTune3 has recently become available for clinical use. The objective of this study is to compare SureTune3 with homogeneous and heterogeneous patient-specific finite element method (FEM) simulations of the VTA to elucidate how well they coincide in their estimates. Approach. FEM simulations of the VTA were performed in COMSOL Multiphysics and compared with VTA from SureTune3 with variation of voltage and current amplitude, pulse width, axon diameter, number of active contacts, and surrounding homogeneous grey or white matter. Patient-specific simulations with heterogeneous tissue were also performed. Main results. The VTAs corresponded well for voltage control in homogeneous tissue, though with the smallest VTAs being slightly larger in SureTune3 and the largest VTAs being slightly larger in the FEM simulations. In current control, FEM estimated larger VTAs in white matter and smaller VTAs in grey matter compared to SureTune3 as grey matter has higher electric conductivity than white matter and requires less voltage to reach the same current. The VTAs also corresponded well in the patient-specific cases except for one case with a cyst of highly conductive cerebrospinal fluid (CSF) near the active contacts. Significance. The VTA estimates without taking the surrounding tissue into account in SureTune3 are in good agreement with patient-specific FEM simulations when using voltage control in the absence of CSF-filled cyst. In current control or when CSF is present near the active contacts, the tissue characteristics are important for the VTA and needs consideration. Clinical. trial ethical approval: Local ethics committee at Linköping University (2012/434-31).

A Novel Method for Power Quality Disturbance Detection Based on LSTM Network Model Residuals

In order to accurately detect the time when the disturbance of power quality (PQ) occurs and the variation of voltage amplitude, a novel method of power quality disturbance detection that is based on the residual of the long short-term memory (LSTM) network model is proposed. Firstly, an offline model is developed based on historical voltage signals from a power grid under the normal condition by using the LSTM theory. Then, in order to detect PQ events online, the grid voltage signal is taken as the input of the model to obtain the residual component between the input signal and the normal signal. Finally, the amplitude change of the residual component reflects the amplitude change of the voltage. The starting and ending time and duration of the disturbance are located by detecting the mutation points of the residual component. Experiments on simulation data and engineering data show that the proposed method can well reflect the amplitude change when the voltage is disturbed, and the disturbance positioning accuracy is high.

High Sensitivity and Wide Range Soft Magnetic Tactile Sensor Based on Electromagnetic Induction

Tactile sensors play a significant role in robotic systems to interact with the external world. In this article, a novel soft magnetic tactile sensor (SMTS) based on the law of electromagnetic induction is proposed. This new sensor uses the configuration of a transformer with planar coils and a Polydimethylsiloxane silicone elastomer with an inverted cone structure embedded in a copper sheet. The SMTS measures the induced voltage amplitude variation of the secondary coil that is caused by the changes in alternating current magnetic field between the coil and the conductive or ferromagnetic sheets. The principle of the new sensor is explained first and then the design methods are outlined. Prototypes are manufactured and a three-dimensional finite element model is built to analyze the mechanical property of the elastomer. Besides, a performance analysis platform and an electronic interface system with the excitation source, the signal processing and the data acquisition, are developed, in order to calibrate the sensor using the polynomial fitting method. The calibrated prototype shows competitive performances in comparison with other existing counterparts, which has a high sensitivity of 56.3 mV/N, a wide measurement range up to 15 N, and a low hysteresis of 2.02%. The new sensor is also of low cost, durable, and has potential applications in dexterous robotic manipulation.

Numerical simulation on the effect of combining centrifugation, electric field and temperature on two-phase separation

The demulsification and dewatering of emulsion is a considerable aspect for the two-phase separation. Though the centrifugation can realize the separation process, the water-in-oil emulsion with high water content and complex components cannot be effectively treated. Therefore, an enhanced two-phase separation process by combing heating process, centrifugation and electric field was proposed in this study. To understand the separation performance of the enhance process, the coupling unit considered temperature variation was taken as the research object, and the effects of main control parameters (voltage amplitude and heating temperature) on flow field and separation efficiency were investigated by numerical simulation and experimental methods. The results demonstrate that the numerical simulation can effectively predict the separation efficiency; the variation of voltage amplitude and heating temperature has a significant impacts on the inner flow field. And based on the centrifugation, combing electric field and heating process can effectively improve the separation efficiency. Specially, the increase of the maximum reverse flow velocity and diameter of reverse flow core can effectively promote the two-phase separation, and the separation efficiency of the enhanced two-phase separation process can be up to 94 % when the optimal parameters are 11 kV and 70 °C, respectively.

T–S Fuzzy Control of Travelling-Wave Ultrasonic Motor

The operation of ultrasonic motor is characterized by obvious nonlinearity. Appropriate motor control strategy is an important prerequisite for promoting the wider application of ultrasonic motors. PID controller is widely used in motor motion control products. Due to the nonlinearity of the ultrasonic motor, the PID control parameter values that can achieve good performance are very different at different speeds. In this paper, aiming at the application requirements of ultrasonic motor speed control, a fuzzy controller with simple structure is proposed to realize nonlinear variable-parameter PID control by using nonlinear input–output mapping ability of fuzzy logic. The proposed fuzzy controller has only one input variable with three linguistic values. In order to match the nonlinear operating characteristics of the ultrasonic motor and improve the control precision, the fuzzy rule is designed as the Takagi–Sugeno form. Takagi–Sugeno defuzzification method is adopted. The calculation formula of control quantity given by the fuzzy controller is similar to that of the PI controller, but the control parameters are nonlinearly changed. Compared with the traditional fuzzy controller, the structure of the proposed controller is simple and the amount of online computations is greatly reduced. Experimental results under various operating conditions show that the proposed controller has good control effect and it has robustness to disturbances such as drive voltage amplitude and load torque variation.

The Control of Squirrel-Cage Induction Electromotor with Constant Magnetization Current

In this paper, we study the control algorithm of electromagnetic torque and rotation speed of squirrel-cage induction electromotor with constant magnetization current. We can ensure the constant magnetization current by acting on stator voltage vector. We distinguish two methods of construction of the given magnetization current. The first method is based on variation of stator voltage amplitude from the information just of rotor rotation speed. The second method is based on the stator voltage frequency and amplitude from the stator current information. The second method permits to influence the characteristic equation roots of the control system and to have magnetization current dynamic properties.

Control of Squirrel-Cage Induction Electromotor with Constant Magnetization Current

In this paper, we study the control algorithm of electromagnetic torque and rotation speed of squirrel-cage induction electromotor with constant magnetization current. We can ensure the constant magnetization current by acting on stator voltage vector. We distinguish two methods of construction of the given magnetization current. The first method is based on variation of stator voltage amplitude from the information just of rotor rotation speed. The second method is based on the stator voltage frequency and amplitude from the stator current information. The second method permits to influence the characteristic equation roots of the control system and to have magnetization current dynamic properties.

Fluctuations of the emission characteristics of multi-tip field cathodes

This paper presents an experimental investigation and modeling of the fluctuations in the electron emission characteristics of the multi-tip field emission cathodes based on composites “disordered carbon nanotubes in a polymer matrix.” A computerized experimental setup recorded the fluctuations of the current–voltage characteristics on the slope-intercept diagram and their motion in accordance with the voltage amplitude variation. Online computer processing of the “glow patterns,” acquired by the field emission projector, allowed the authors to estimate a local field enhancement factor of the microscopic emission sites. These data were used in the computer model of the adsorption–desorption process on the cathode surface. The results of the modeling showed good agreement with the experimental results. The present model has great potential for predicting the behavior of the multi-tip field cathodes.

Exposure level from selected base station tower around Kuala Nerus: a preliminary analysis

Health risk due to RF radiation exposure from base station tower (BST) has been debated for years leading to public concerns. Thus, this preliminary study aims to measure, evaluate and analyze the exposure level on three selected BST around Kuala Nerus. The measurement of exposure level in terms of voltage amplitude (dBmV) data were recorded using spectrum analyzer. The trend of exposure level shows that the characteristics of environment around the BST sites contribute to the variation of voltage amplitude for all study sites. Besides, the radiation exposure level of BST depends on several factors such as: the distance from the radiation sources, the height of the tower, tilt and direction of the antennas fixed on the top of the tower, the number of antennas on single tower, the type of radiation pattern, the direction of main beam of radiation, the feeding power and the operating frequency

DC Bus Voltage Control of a Power Generation System Based on a Dual Star Induction Generator

The main objective of this paper is the study and the evaluation a squirrel-cage Dual Star Induction Generator (DSIG) performances. This generator can be used in energy production at variable speed for high-power wind or hydro turbines. The studied system consists of a DSIG feeding a static load through two voltage source inverters connected in parallel on the same DC bus. A DC motor is used to ensure the generator drive at variable speed. This scheme is chosen to avoid the generated voltage amplitude and frequency variations, which occurs in case of self-excited induction machine and depends on the rotating speed and the size of the excitation capacitors. Thus, Modeling of DSIG, in the synchronous reference frame, and different parts of generation system are given. Then control strategy development is detailed. To ensure DSIG excitation and DC bus regulation under variable speed and at different loads, a control strategy based on active and reactive power control principle is used. Finally, power generation system performances are validated by simulation and confirmed by a set of experiments, carried out on an experimental test bench composed DSIG driven by DC motor. Simulation and experimental results show that the DC bus voltage is well regulated under different mode operating.

A Novel Efficient Sine Wave Inverter with Custom Programmed PWM and Intelligent Control

This article presents an efficient design of a pure sine wave inverter which results in an electronic design with reduced losses. The proposed design incorporates the generation of custom programmed pulse width modulation (CPPWM) waveforms; the gate drive signals that are customized for the harmonic elimination from the output voltage, maximizing the fundamental component and resulting in an efficient electronic circuit design as compared to the traditional techniques in terms of the switching losses and the filtering energy losses. The CPPWM signals are digitally programmed in a micro-controller. The inverter realization is followed by an intelligent compensator design for the regulation of output voltage amplitude. The proposed algorithm self-adjusts its parameters in response to the load current and voltage amplitude variations hence resulting in an improved performance. The simulation results of the control algorithm are presented. The experimental validation of the theoretically investigated controller is also presented by implementing a discrete time realization of the control algorithm using digital controller interfaced in real time with MATLAB®/Simulink®. The hardware results are elucidated. The feasibility of the proposed controller is theoretically and experimentally verified by its efficiency compared to the classical techniques, the available tunable parameters in the controller structure and the immense flexibility in the attainable closed loop dynamics.

A Novel Efficient Sine Wave Inverter with Custom Programmed PWM and Intelligent Control

This article presents an efficient design of a pure sine wave inverter which results in an electronic design with reduced losses. The proposed design incorporates the generation of custom programmed pulse width modulation (CPPWM) waveforms; the gate drive signals that are customized for the harmonic elimination from the output voltage, maximizing the fundamental component and resulting in an efficient electronic circuit design as compared to the traditional techniques in terms of the switching losses and the filtering energy losses. The CPPWM signals are digitally programmed in a micro-controller. The inverter realization is followed by an intelligent compensator design for the regulation of output voltage amplitude. The proposed algorithm self-adjusts its parameters in response to the load current and voltage amplitude variations hence resulting in an improved performance. The simulation results of the control algorithm are presented. The experimental validation of the theoretically investigated controller is also presented by implementing a discrete time realization of the control algorithm using digital controller interfaced in real time with MATLAB®/Simulink®. The hardware results are elucidated. The feasibility of the proposed controller is theoretically and experimentally verified by its efficiency compared to the classical techniques, the available tunable parameters in the controller structure and the immense flexibility in the attainable closed loop dynamics.

Reduction of Losses at the Start-up of DC Motor Using the Voltage Amplitude Variation Law

Reduction of Losses at the Start-up of DC Motor Using the Voltage Amplitude Variation Law

Inducverters: PLL-Less Converters With Auto-Synchronization and Emulated Inertia Capability

Inspired by induction machines working principles, this paper presents the idea of phase-locked-loop-less (PLL-less) operation of grid-connected voltage source converters (VSCs) under new concept of inducverter. The proposed controller eliminates the need for a dedicated synchronization process and the related PLL, and therefore it offers a simpler and more reliable control strategy compared to the conventional methods. In addition, it represents an improved performance, as it provides real and true auto-start and auto-synchronization with a grid without the need for grid voltage information. A current damping/synchronization unit enables grid auto-synchronization by using local current information and can track grid voltage frequency, angle, and amplitude variations while feeding constant amount of power, which is of high-interest in frequency varying grids and also in the case of grid voltage angle jump. Another advantage of the inducverter is that it introduces virtual inertia to the grid to regulate frequency, which enhances frequency dynamics of smart grids. Beside the current synchronization unit, the proposed strategy has a single-loop controller core with control over both power and current, which is implemented in a hybrid dq and abc frame using a virtual adaptive lead or lag impedance. The controller also offers stable and high-performance synchronization and operation under unbalanced and/or distorted grid conditions. The work beside synchronous current converters gives a bird’s eye view to research in the new area of PLL-less and virtual inertia-based operation of VSCs and fulfill a unified set of controllers for the smart grid integration. Simulation, hardware-in-loop, and experimental results are presented to validate effectiveness of the controller.

The Influence of Supply Voltage Amplitude Variation Law on AC Induction Motor Efficiency in Variable-Speed Drive

This paper presents investigation results of the influence of the supply voltage amplitude variation law on the efficiency of AC induction motor in variable-speed drive based on the frequency converter. It is demonstrated that the commonly employed linear and square voltage amplitude variation laws do not provide the highest efficiency of the AC induction motor. The corrected AC voltage amplitude variation dependences for different motor load torque, at which high efficiency of the motor supplied by the frequency converter is maintained, are proposed and discussed. Reported experimental study was performed on a special test bench.

Laser based optical sensor for vibration measurements

This paper presents a technique for detection and measurement of vibrations especially in machine design. This technique makes use of a He–Ne laser and has decisively an edge over the conventional methods, which have certain limitations regarding their vibration measurements due to their contact nature. However, in the present study, the method used is a non-contact one. In this case, the measurements include variation of voltage amplitude with rotor speed and variation of vibration frequency with rotor speed. Calibration studies are also conducted.