No-load State Research Articles

Rotor Speed Prediction Model of Multi-Rotor Unmanned Aerial Spraying System and Its Matching with the Overall Load

During continuous spraying operations, the liquid in the pesticide tank gradually decreases, and the flight speed changes as the route is altered. To maintain stable flight, the rotor speed of a multi-rotor unmanned aerial spraying system (UASS) constantly adjusts. To explore the variation law of rotor speed in a multi-rotor UASS under objective operation attributes, based on indoor and outdoor experimental data, this paper constructs a mathematical model of the relationship between rotor speed and thrust. The model fitting parameter (R2) is equal to 0.9996. Through the neural network, the rotor speed prediction model is constructed with the real-time flight speed and the payload of the pesticide tank as the input. The overall correlation coefficient (R2) of the model training set is 0.728, and the correlation coefficients (R2) of the verification set and the test set are 0.719 and 0.726, respectively. Finally, the rotor speed is matched with the load of the whole UASS through thrust conversion. It is known that the single-axis load capacity under full-load state only reaches about 50% of its maximum load capacity, and the load increase is more than 75.83% compared with the no-load state. This study provides a theoretical and methodological reference for accurately predicting the performance characterization results of a power system during actual operation and investigating the dynamic feedback mechanism of a UASS during continuous operation.

Analysis Optimization and Comparison to Detect Failures in the Squirrel-Cage Rotor using High-Level Wavelets

The methods and tools used for signal analysis extracted from the induction motors, such as the motor current signature analysis (MCSA) used for data collection on a non-invasive basis, the multi-resolution analysis (MRA) and discrete wavelet transform (DWT), are efficient tools for the signal analysis at different levels or resolutions, these tools have been applied together to improve detection of failures in the rotor of induction motors in condition of no-load. This work focuses on the study of rotor cage end ring, in a condition with lower-load or no-load where uncertainty predominates, this area of study is complicated to analyze correctly with conventional methods, but in these circumstances, the analysis using TDW has better performance. The article presents an alternative way of detecting failures in three phases induction motors in no-load state method with an optimized method and a comparison between results of the analysis with two different levels of the high-order Wavelet Daubechies, studying and evaluating its performance for the detection of broken ring, all this supported with a specific signal pre-processing and post-processing to improve the results of detection in incipient faults.

Transient-steady state vibration characteristics and influencing factors under no-load closing conditions of converter transformers

The converter transformer plays a key role in the HVDC transmission project. It will be put back into the power grid after a power outage for maintenance. The transient overvoltage and excitation inrush current during charging and closing will cause shock vibration and affect the stability of the internal mechanical structure. In addition, the on-load tap-changer (OLTC) shifting operation after closing will also lead to changes in the vibration characteristics. Because of insufficient research on vibration during closing transient and no-load operation, this paper measures the transient vibration change process during no-load closing and tap-changer action in a ± 800 kV converter station. Furthermore, the influence of voltage and winding turns changes on no-load vibration is also analyzed, and multi-characteristic parameters of vibration impulse factor, offset factor, and odd–even harmonic ratio are extracted to realize no-load state identification. The results show that the no-load vibration increases with the increase of the voltage, and decreases with the increase of the number of turns of the grid-side winding. More importantly, both the charging closing and the tap-changer action will produce vibration and shock components, and the maximum transient vibration exceeds 90 m/s2, which is 35.7 times that of the steady-state. Odd harmonic components of 50 Hz, such as 150 Hz, 250 Hz, etc., will appear in the vibration spectrum under the action of the 2nd, 4th, and other even harmonics in the excitation inrush current. While the non-excitation inrush current is mainly an even multiple of 50 Hz. The research results reveal the vibration characteristics of the converter transformer during closing transient and no-load operation, and provide a theoretical reference for the evaluation and identification of the converter transformer under all operating conditions.

Mechanical characteristics analysis and control algorithm for floating raft system with mass variation

The ship floating raft system adopts the integrated design of large liquid tanks and rafts, which can optimize the arrangement in the cabin and increase the intermediate mass of the system to achieve efficient vibration isolation of equipment. One of the major challenges is that the change of liquid mass in the tank will cause displacement of the raft, which will change the modal characteristics of the system and affect the stability of the vibration isolation system performance. This paper establishes a mechanical analysis model of a floating raft system under time-varying liquid mass conditions. Taking a ship variable mass floating raft system as the research object, the effect of mass change on the characteristics of raft displacement, isolator load distribution, and modal frequency of the vibration isolation system is analyzed. The analysis shows that when the liquid tank goes from full load to no-load state, its mass change accounts for 40% of the total mass of the raft, which will cause a large displacement of the raft and change the low order modal frequency of the system, bringing the risk of equipment safety and vibration isolation performance degradation. Therefore, an adaptive variable load control method is proposed to realize the raft attitude balance and load equalization optimization under the variable mass condition of the floating raft air spring system. The test results show that the proposed control method can automatically adapt to the large mass gradual change from full load to no load of the liquid tank on the raft, and control the displacement of the raft structure from about 10 mm to 1.5 mm, which effectively ensures the stability of the air spring system performance.

Design advantages and analysis of a novel five-phase doubly-fed induction generator

PurposeThe purpose of this paper is to provide an analysis of the performance of a new five-phase doubly fed induction generator (DFIG).Design/methodology/approachThis paper presents the results of a research work related to five-phase DFIG framing, including the development of an analytical model, FEM analysis as well as the results of laboratory tests of the prototype. The proposed behavioral level analytical model is based on the winding function approach. The developed DFIG model was used at the design stage to simulate the generator’s no-load and load state. Then, the results of the FEM analysis were shown and compared with the results of laboratory tests of selected DFIG operating states.FindingsThe paper provides the results of analytical and FEM simulation and measurement tests of the new five-phase dual-feed induction generator. The use of the MATLAB Simscape modeling language allows for easy and quick implementation of the model. Design assumptions and analytical model-based analysis have been verified using FEM analysis and measurements performed on the prototype. The results of the presented research validate the design process as well as show the five-phase winding design advantage over the three-phase solution regarding the control winding power quality.Research limitations/implicationsThe main disadvantage of the winding function approach-based model development is the simplification regarding omitting the tangential airgap flux density component. However, this fault only applies to large airgap machines and is insignificant in induction machines. The results of the DFIG analyses were limited to the basic operating states of the generator, i.e. the no-load state, the inductive and resistive load.Practical implicationsThe novel DFIG with five phase rotor control winding can operate as a regular three-phase machine in an electric power generation system and allows for improved control winding power quality of the proposed electrical energy generation system. This increase in power quality is due to the rotor control windings inverter-based PWM supply voltage, which operates with a wider per-phase supply voltage range than a three-phase system. This phenomenon was quantified using control winding current harmonic analysis.Originality/valueThe paper provides the results of analytical and FEM simulation and measurement tests of the new five-phase dual-feed induction generator.

Modeling of Rapid Response Characteristics of Piezoelectric Actuators for Ultra-Precision Machining

Piezoelectric actuators are characterized by high positioning accuracy, high stiffness and a fast response and are widely used in ultra-precision machining technologies such as fast tool servo technology and ultrasonic machining. The rapid response characteristics of piezoelectric actuators often determine the overall quality of machining. However, there has been little research on the fast response characteristics of piezoelectric actuators, and this knowledge gap will lead to low precision and poor quality of the final machining. The fast response characteristics of a piezoelectric actuator were studied in this work. Firstly, the piezoelectric actuator was divided into a no-load state and a load state according to the working state. A fast response analysis and output characteristic analysis were carried out, the corresponding dynamic model was established, and then the model was simulated. Finally, an experimental system was established to verify the dynamic model of the piezoelectric actuator's fast response by conducting an experiment in which the piezoelectric actuator bounces a steel ball. The experimental results verify the correctness of the model and show that the greater the cross-sectional area and height of the piezoelectric actuator, the higher the bouncing height of the ball, and the better the dynamic performance of the piezoelectric actuator. It is believed that this study has guiding significance for the application of the dynamic characteristics of piezoelectric actuators in the machining field.

Rice threshing state prediction of threshing cylinder undergoing unbalanced harmonic response

When the cylinder of rice combine harvester is threshing, the interaction between the fed rice stalk and the threshing teeth makes the cylinder subject to a large vibration shock. Undergoing the influence of this shock, the vibration response of threshing cylinder is non-stationary. In view of the above problems, this paper aims to accurately characterize the harvesting state of the threshing cylinder and extract the impact components caused by the winding of rice stalks. First, the constrained modes and main response harmonics of the threshing cylinder during operation are solved by modal harmonic response analysis. The time-frequency domain analysis was carried out on the threshing cylinder vibration signal undergoing field working conditions. Combined with spectral envelope and spectral kurtosis analysis methods, the main shock frequencies during the threshing process of the cylinder are analyzed. The results show that the main response frequency of the threshing cylinder under no-load state is the response frequency of 14 Hz, but the main frequency component of the threshing cylinder during the harvesting process is 80 Hz. Comparing the results of harmonic response analysis, it can be concluded that the winding of rice stalks will affect the vibration response of the threshing cylinder. Rice threshing state prediction with harmonic response provides a new method for the follow-up threshing cylinder condition monitoring and fault diagnosis.

Effect of Dielectric Relaxation of Epoxy Resin on Dielectric Loss of Medium-Frequency Transformer

Epoxy resin (EP) is a typical and widely used insulating material for medium-frequency transformers (MFTs). The dielectric loss of EP is one of the key variables in the design and operation of MFT. In this article, six types of epoxy/anhydride systems are prepared, and the dielectric loss of MFT is calculated by finite element method (FEM) analysis based on broadband dielectric spectroscopy measurements. The material dependence of the dielectric loss of MFT is investigated using dielectric spectroscopy and molecular dynamics simulations over a wide temperature and frequency range. The results show that the variation of dielectric loss with output power is attributed to the temperature characteristics of the imaginary part ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon ^{\prime \prime }$ </tex-math></inline-formula> ) of complex permittivity. Compared to the dielectric loss at no-load state, the one at rated power is reduced by 5–10 W. The anhydride hardener containing benzene ring or a methyl substituent has an inhibitory effect on dielectric loss, and the EP cured by methyl nadic anhydride (MeNA) has the lowest dielectric loss (16.2 W) at rated power. The dielectric loss and overload characteristics of MFT are closely related to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -relaxation and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -relaxation of EP, respectively. The acid anhydride curing agent containing benzene ring or a methyl substituent reduces the temperature corresponding to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -relaxation peak by more than 50 °C compared to the one without. The increased rigidity of the chain segment of EP makes the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -relaxation move to the low-temperature side, which is beneficial to suppress the dielectric loss. This article not only serves as a bridge among dielectric loss of MFT, dielectric spectroscopy, and molecular structure of EP but also lays a solid foundation for the selection of insulating materials for MFT.

Performance of an oxygen-consuming inerting system for an aircraft fuel tank with RP-3 aviation fuel in flight

Aircraft fuel tank inerting system is an important guarantee for flight safety. A novel oxygen-consuming inerting system-3CIS (low-temperature controllable oxygen-consuming catalytic inerting system) was proposed and studied with RP-3 aviation fuel. Based on the designed inerting system, the mathematical model of the system in flight was established based on the conservation law of mass and energy. The system performance under different flight conditions was firstly analyzed, and the effects of the initial fuel loading, fan flow rate and preheating temperature on the system performance were studied. Meanwhile, a test bench was built to verify the correctness of the established model. The following conclusions can be drawn from the results: The 3CIS can reduce the oxygen concentration in the fuel tank quickly to prevent fires and suppress explosions. What's more, the inerting time is the longest when the fuel tank is initially empty if all other system conditions are the same. Therefore, it is suggested the no-load state should be used for the system parameters design for the purpose of maximum safety. As for the influence of key parameters on system performance, the inerting rate increases with the increase of fan suction flow and preheating temperature, and low fan flow rate during the climb and cruise stages and high fan flow rate during descent are suggested for the control system designing. Finally, a regenerator is recommended when designing the system since it can effectively reduce the preheating power and cooling power of the system.

Analysis of Damping Characteristics of a Hydraulic Shock Absorber

In the present study, a hydraulic shock absorber is proposed. Since the damper is mainly used in suspension energy recovery system, the damping characteristics of the damper under no-load state are studied in this paper. Structural design is conducted so that the unidirectional flow of the oil drives the hydraulic motor to generate electricity. Meanwhile, an asymmetrical extension/compression damping force is obtained. A mathematical model of the shock absorber is established, and the main characteristics of the inherent damping force are obtained. Based on the established model, effects of the accumulator volume, accumulator preinflation pressure, hydraulic motor displacement, check valve inner diameter, and spring stiffness, hydraulic line length and inner diameter on the indicator characteristics are analyzed. Moreover, a series of experiments are conducted on the designed damper to evaluate the characteristics of the inherent damping force and analyze the effect of the accumulator volume and preinflation pressure on the damping characteristics.

170㎸ 가스절연개폐기용 차단 접점 마모에 따른 기계적 열화 특성 분석

This paper deals with the effect of mechanical wear on the contact of circuit breaker applied to the 170㎸ Gas Insulated Switchgear (GIS). The arc occurrence was ignored to verify the pure effect of mechanical wear on the contact of circuit breaker. Since only the effect of the mechanical wear was considered, the experiment was carried out under no-load state. The accelerated test method was adopted and the specimens were operated until the lifetime same as actual 170㎸ GIS contact. The specimens were tripped and closed up to 20,000 times and the its electrical resistances and weights were measured at regular intervals. Based on the test results, the correlation between mechanical wear of contact and trip/close coil current was analyzed. The analysis result showed that, even the slight mechanical wear of contact can cause delays in the trop/close operation of the GIS.

Electromagnetic simulation of an external rotor PM hub motor power device for distributed driving electric vehicle

In order to increase efficiency and reliability of hub motor power device for distributed driving electric vehicle, a novel hub motor with an external rotor PM (permanent magnet) is designed and optimized. The performance parameters of hub motor are computed and selected based on vehicle dynamics indicators and the driving equations. This paper determines the optimum primary size of hub motor by choosing appropriate magnetic circuit structure and integrating three key parameters, including as stator split ratio, electromagnetic load and viscous damping coefficient. This paper has built the analysis model of external rotor PM hub motor, and simulated and analyzed the transient magnetic field of hub motor under no-load and load transient or steady state. Simulation results indicate that the external rotor PM hub motor designed by combining stator split ratio, electromagnetic load and viscous damping coefficient has satisfactory electromagnetic performance, which can satisfy the performance requirements and indicators of hub motor power device for distributed driving electric vehicles.

Energy Saving Analysis of No-load Loss of Electric Welding Equipment

In this paper, two types of electric welding equipment are studied. First of all, YD / k-505fl4 and bx3-500 type welding machines do not have the function of self power off in standby state. It is necessary to install an intelligent welding machine power saving system to control the power off of the primary side of the transformer under the no-load state of the welding machine, and then cut off the no-load loss of the welding machine. Secondly, yd-500-kr II series welding machine has the function of standby, delay and self power off. Due to the unreasonable setting of welding parameters, the uneconomical selection of welding cable and the unreasonable layout of welding machine, the overall energy loss of welding machine is large. Finally, weathering steel is used in the welding process design, and the performance, energy consumption and economic practicability of the material are analyzed.

A Novel Piecewise Velocity Control Method Using Passivity-Based Controller for Wave Energy Conversion

By studying the working principle of a maximum power point tracking (MPPT) method called active phase control (APC), we found that not only was the phase difference between the wave excitation force and the velocity reduced, but also the magnitude of the velocity increased. For the direct-drive wave energy converter with a permanent magnet linear generator (PMLG), the velocity of the PMLG in the no-load state is larger than that in any power generation states. According to this characteristic, a novel piecewise velocity control (PVC) method and its trajectory planning scheme for a sealed-buoy wave energy converter (SBWEC) are proposed to obtain the maximum power extraction condition. Considering the irregularity of ocean waves and that the proposed method needs to frequently change the operating state of the PMLG, a passivity-based controller (PBC) is designed. With energy modification and damping injection, rapid convergence and asymptotic stability of the system are guaranteed, so that the proposed MPPT method can be perfectly implemented. The comparative simulation results for regular and irregular waves demonstrate that it is an effective and promising power control method.

AISI 4140 시편의 미세단조 공정 충격력 및 표면 변형량 측정

The micro-forging process improves the surface quality of the workpiece by micro tip impacting. In this study, the impact force is generated using a terfenol-D oscillator (ETREMA Product. lnc.), and it is measured when the actual impact is in action. The experimental results show that the amplitude of the force in the no-load state is approximately 325.6 N, and the impact force is 116.6 N and 118.6 N when the static load is changed. As the output of the oscillator was changed by energy loss and structural damping, the impact force was found to be as 29.1 N and 36.4 N, respectively. The impact test was performed on the AISI 4140 specimen under these conditions, and the deformation of the surface was measured and compared. Hence, the impact force measurement results obtained in this study can be used as an important parameter for the optimization of micro-forging process.

Unbalanced Vibration Identification of Tangential Threshing Cylinder Induced by Rice Threshing Process

Unbalanced vibration of tangential threshing cylinder increased the grain loss, shortened service life of the cylinder, and resulted in structural resonance during the rice threshing process. In this paper, the vibration amplitude and frequency of tangential threshing cylinder shaft were tested, and the vibration state of tangential threshing cylinder was identified. The restricted and working modalities of tangential threshing cylinder were solved by ANSYS software. Then, by comparing the resonance phenomenon between the inherent constraint frequency and the rotation speed frequency, the shaft vibration under the idle condition of tangential threshing cylinder was tested and analyzed. According to the axial vibration and axial trajectory of the cylinder, the inherent properties and characteristics of unbalanced vibration were revealed. Test results showed that when the tangential threshing cylinder was at idling and no‐load state, the amplitude of vibration in the feed direction of straw flow was −0.049~0.060 mm, and the average vibration amplitude was 0.013 mm. As rice flowed along the tangential threshing cylinder, the vibration amplitude slightly increased. The trend and phase of each trajectory were similar, although the amplitude of each trajectory was different. The tangential threshing cylinder axis trajectory was flat oval. Unbalanced vibration was induced by the rice stalks in the concave gap.

Estimating Surface Temperature of a Calibration Apparatus for Contact Surface Thermometers from Its Internal Temperature Profile

A calibration apparatus for contact surface thermometers was developed. Temperature of the upper surface of a copper cube of the calibration apparatus was used as reference surface temperature, which was estimated at around $$50\,{^{\circ }}\hbox {C}$$ , $$100\,{^{\circ }}\hbox {C}$$ , and $$150\,{^{\circ }}\hbox {C}$$ by not only two conventional industrial platinum resistance thermometers (IPRTs) but also five small-sized platinum resistance thermometers (SSPRTs) calibrated based on the International Temperature Scale of 1990 (ITS-90). These thermometers were inserted horizontally into the copper cube and aligned along the center axis of the copper cube. In the case of a no-load state without anything on the upper surface, the temperature profile inside the copper cube linearly decreased from the lower part to the upper surface, which suggests that the heat conduction inside the copper cube can be regarded as a one-dimensional steady state. On the other hand, in the case of a transient state just after the contact surface thermometer was applied to the upper surface, the temperature profile became a round shape. We obtained good agreement between the curvature of the temperature profiles and the results estimated by using an error function used for a one-dimensional transient heat conduction problem. The temperature difference between the estimated temperature by linear extrapolation using two IPRTs and that by extrapolation using the error function was within $$0.2\,{^{\circ }}\hbox {C}$$ in the transient state at around $$150\,{^{\circ }}\hbox {C}$$ . Over 10 min after the contact surface thermometer was applied, the temperature profile showed a linear shape again, which indicated that linear extrapolation using two IPRTs was well for the estimation of the reference surface temperature because the heat conduction state inside the copper cube came back to the one-dimensional steady state. Difference between the surface temperature and temperature detected by the contact surface thermometer was also observed after the contact surface thermometer touched on the upper surface. The difference was over $$0.1\,{^{\circ }}\hbox {C}$$ at several minutes after the contact surface thermometer touching on the reference surface and was suppressed with passing time in the transient state and became negligible over 10 min.

Comparison of higher harmonic contents in salient pole synchronous generator with different rotor construction

Abstract The paper presents a comparison of higher harmonics in induced phase voltages of a stator winding in the no-load state of a three-phase 5.5 kVA salient pole synchronous generator. The comparison is carried out for the synchronous generator with different salient pole rotor constructions: a non-skewed solid rotor, a non-skewed solid rotor with radial incisions, and a laminated electrotechnical steel rotor with skewed slots and damping bars. The calculations of higher harmonics are based on the magnetic field distributions in the air gap, which are carried out in a 2D model in a FEMM program and on the induced voltage waveforms in the stator windings registered during experimental investigations of the 5.5 kVA salient pole synchronous generator in the no-load state.

A study on flow distribution for integrated hybrid actuator by analysis of reed valve

Many studies have been conducted recently on an integrated hybrid actuator due to the increasing need for unmanned aircraft and guided weapons. In this study, flow distribution was analyzed for a reed valve which was used for flow regulation to improve the performance of the actuator. By using a Fluid structural interaction (FSI) technique with Computational fluid dynamics (CFD) having a moving mesh, numerical analysis was performed according to the thickness, shape and driving frequency of the reed valve. From the calculated results, the maximum performance of the reed valve was found at the valve thickness of 0.15 mm and the driving frequency of 250 Hz for a no-load state. The optimum thickness and shape for the valve for each driving frequency were also realized.

Noise and Vibration Measurements for the Assessment of Damping Efficiency in Power Transformers

Power transformers emit a very characteristic harmonic sound during operation. The sound spectrum consists of the harmonics of double frequency of the power grid with the fundamental of 100Hz or 120Hz in different countries around the world. This fundamental frequency dominates in the sound spectrum during the load condition while the higher harmonics are representative for the no-load operating state. Regardless of loading conditions, all the harmonics build rather unpleasant noise, which is difficult to suppress. Moreover, this noise is sometimes difficult to measure and interpret, due to the harmonic nature and a content of harmonics of relatively low frequencies.This paper presents the exemplary study on the assessment of noise damping efficiency, performed with the use of laser vibrometry and sound intensity measurements, which can provide the most complete information, when it comes to the identification of the sources of noise as well as to the proper evaluation of damping solutions.