Slip Ring Research Articles

Influence of Electric Current on the Wear Topography of Electrical Contact Surfaces

Abstract Wind pitch slip ring consists of several circuits applied with changing electric current, which makes the wear mechanism extremely complicated. The aim of this paper is to study the influence of electric current on the wear behavior of friction pair using a ball-on-disc tribometer. The wear test was carried out with normal loads of 10 N and 15 N and applied electrical current ranging from 0.5 to 20 A. Wear topographies without electric current, with small (0.5–5 A) and large (5–20 A) electric current, were analyzed. The characteristic parameters (surface roughness, wear volume, and multifractal parameters) were used to comprehensively characterize the wear topography. The results indicate that the characteristic parameters of topography without current are the smallest. The main wear mechanism of friction pair without current is adhesion wear. The characteristic parameters fluctuate in a large range for the small current. The main wear mechanism of ball sample is adhesion wear with slightly arc ablation, but that of the disc sample is adhesion wear. The characteristic parameters increase with the electric current for the large current. The main wear mechanism of the ball sample is the interaction of adhesion wear and arc ablation, but that of disc sample is adhesion wear with slightly arc ablation. The electric current will aggravate the wear of friction pair and increase the singularity and complexity of the surface. The results are of great significance for guiding anti-wear design of wind pitch slip ring.

Design, Manufacture, and Test of a Rotary Transformer for Contactless Power Transfer System

In traditional applications such as machine field excitation, where power transfer from stationary to rotary side is needed, contact slip rings are often adopted. However, this kind of slip ring is easy to wear and needs frequent maintenance. In a contactless power transfer system, mechanical slip rings can be removed which will largely increase the system reliability. In this article, a contactless power transfer device using wireless power transfer (WPT) is designed. Its performances are simulated by finite-element method. To increase the system power rate and efficiency, the device is operated under high frequency. Thus, high-frequency ferromagnetic materials and Litz wires are used. Moreover, compensation circuits are added to improve the coupling between the primary and secondary sides. At last, a prototype is built and tested. From the experimental results, the functions and performances of the device are well verified.

A Comparative Study of Dual Stator With Novel Dual Rotor Permanent Magnet Flux Switching Generator for Counter Rotating Wind Turbine Applications

Compared with the single rotor wind turbine, a counter-rotating (CR) wind turbine with two rotor sets leads to twice power density. In this regard, dual stator CR (DSCR) permanent magnet flux switching generator (DSCR-PMFSG) is employed. However, in DSCR-PMFSG both rotor and armature parts are rotating and require slip rings for power transmission. These slip rings associate demerits of constant maintenance, poor speed regulation, increased cost, and additional slip ring losses, whereas DSCR-PMFSG offer lower flux and lesser power density. To overcome the demerits of DSCR-PMFSG as mentioned earlier, this paper proposed a novel dual rotor counter-rotating permanent magnet flux switching generator (DRCR-PMFSG) for wind turbine applications that eliminate the requirements of slip rings and retain brushless operation. The proposed DRCR-PMFSG share one stator connected back-to-back through a flux bridge that provides an alternate flux path between two mechanical ports associated with the inner rotor and outer rotor, contributing to the cumulative output. A detailed comparative analysis of DSCR-PMFSG and DRCR-PMFSG is performed under static characteristics, overload, and wide speed range to generate output power, voltage, current, power density, and efficiency. Quantitative comparative analysis under static analysis evident that proposed DRCR-PMFSG exhibits 33.29% higher flux, suppressed cogging torque and torque ripples up to 53.48% and 67.45%, respectively. Furthermore, a comprehensive quantitative analysis is performed under coupled overload and over-speed capability. Analysis exposes that in comparison with DSCRP-PMFSG, the proposed DRCR-PMFSG improves voltage regulation factor by 55.88%, output current enhanced by 67.9%, raise output voltage to 2.01 times, and power density to 1.72 times while maintaining the efficiency of 90.195% and achieving stable voltage profile with load variation. Finally, a detailed comparative analysis with conventional designs is performed and comprehensive mathematical modelling based on sub-domain model is developed accounting stator slot and rotor pole combinations, magnetic saturation, and winding configuration to validates finite element analysis (FEA) of JMAG Designer v.20.1.

Overview of Research and Development on Space Slip Rings

Overview of Research and Development on Space Slip Rings

Real Time Simulation of Brushless Doubly Fed Reluctance Generator Driven Wind Turbine Considering Iron Saturation

Brushless doubly fed reluctance generator (BDFRG) provides a good substitute for the doubly fed induction generator for the wind energy applications due to the nonexistence of the slip rings. Real time modelling of the BDFRG is a challenge due to the high leakage inductance of the stator windings. While the magnetic saturation of the iron parts affects the inductances values, therefore studying the effect of magnetic saturation on the BDFRG performance is important. In this paper, a BDFRG model including iron saturation is built. The finite element (FE) analysis using FEMM software is used to generate the relationship between the generator currents and the inductances, the generated data are recorded in a lookup table. A Simulink model of the BDFRG driven wind turbine, with two cases of constant and variable inductances, are developed and verified with FE analyses at range of wind speeds above and below the synchronous speed. The lookup table proposes is verified using finite element analysis at different modes of operation of wind speed and compared with the constant inductance model to show the importance of saturation inclusion in the generator model for accurate generator modelling representation.

Comprehensive Diagnostics of the Technical Condition of a Turbine Generator Slip Ring Current Collector

Comprehensive Diagnostics of the Technical Condition of a Turbine Generator Slip Ring Current Collector

Six Cases of Philips Ingenuity CT Maintenance

The article describes the failure phenomenon, analysis and processing process of the high-voltage generator module, FRC unit, rack tilt circuit and slip ring system in the daily use of Philips Ingenuity CT, so as to sum up the experience, discuss with the medical staff, and further Deepen the understanding of Philips Ingenuity CT's structure and working principle, and jointly improve the maintenance skills of CT and other large equipments.

Design and transient experimental analysis of a pulsed brushless doubly fed alternator in a capacitor charge power supply system

There is an urgent need to develop a robust capacitor charge power supply (CCPS) system to meet the requirement of pulsed load in all-weather mobile occasions such as vehicle, ship and aircraft. Brushless doubly fed alternator (BDFA) works through the rotor's pole pairs' transformation to get excitation indirectly, without magnets, brushes and slip rings. Both DC and AC excitation can be used. Therefore, it has high reliability and a good application prospect in the CCPS system. However, the existing research studies lack analysis of the parameters that affect charging performance, and have no experimental analysis of the prototype. To solve this problem, a comprehensive design method and experimental procedure of the pulsed BDFA are proposed and investigated. First, the operation principle of the pulsed BDFA is illustrated. Then, the charging performances under different design schemes are comparatively analysed through the finite element analysis (FEA). Finally, a prototype of the pulsed BDFA is manufactured, and the related experiments are carried out. The results verify the feasibility of the experimental procedure and the accuracy of FEA. The comprehensive design method and experimental procedure in this work provide a straightforward reference for the subsequent applications in the CCPS system.

Analysis of Slip Ring Induction Motor Drive Using Slip Power Recovery Scheme with Inverter and Chopper Control for Id Fan in Power Plant

Abstract: Induction motors are used as industrial drive and for various applications in power plant due to their rugged, robust and simple construction as well as low cost. The speed control of SRIM is dexterous by slip power recovery scheme consisting of inverter control, chopper control, and rotor resistance control techniques. This paper presents the boost in the performance characteristics and energy saving of SRIM drive by inverter and buck-boost chopper based slip power recovery scheme (SPRS). The simulation model of a WRIM drive using inverter and based buck-boost chopper control has been executed in the Simulink platform. The simulation results using inverter and chopper control have been studied. The active power and reactive power have been taken as parameter for analyzing the energy saving by the drive. The simulation result has shown that inverter chopper control SPRS large amount of energy saving.

Analysis of Contact Characteristics of Carbon Brush/Slip Ring under Eccentric Oscillation of Hydrogenerator Rotor

In this paper, the contact characteristics of the carbon brush/slip ring of the hydrogenerator under the eccentric vibration of the rotor are studied. The influence of spring parameters on the contact loss of the carbon brush/slip ring was studied by establishing the motion model of the carbon brush/slip ring for theoretical calculation and fitting the motion trajectory curve with MATLAB software. Studies have shown that the loss of contact is mainly related to the spring damping coefficient and the precompression. By optimizing these two parameters, the contact stability of the carbon brush on the ring surface of the slip ring can be improved. It provides a theoretical reference for the design and optimization of the parameters of the carbon brush/slip ring spring.

Design of a small disc-type coreless permanent magnet brushed DC actuator

Purpose Design of small disc-type permanent magnet (PM) brushed DC motors for servomechanisms is challenging. The purpose of this paper is to propose a special coreless double-sided structure. This easy to manufacture motor has two set of shifted concentrated windings on both sides of the rotor. All of the coils in each winding are simply connected in series. A simple arcless commutator, which shares the features of both the usual commutators and slip rings, is connected to each winding at only two points. Design/methodology/approach By replacing the PMs with an equivalent current density, main design equations of the motor have been derived through the solving of scalar Poisson equation. A radial division technique has been used to take the radial variations into account. This provides the ability of considering various shapes of coils and PMs. A novel iterative algorithm has been proposed to design a motor with high torque capability, compared to other coreless counterparts. Some design variables are obtained based on an independent optimization problem, which maximizes the active portion of windings. The other variables are calculated in such a way that the design requirements are satisfied. Findings The feasibility and capability of the new structure have been proved by prototyping a sample motor. Comparing the design outputs with the results of the 3D finite element analysis and experimental tests shows a good agreement. This verifies the accuracy of the proposed design method. Originality/value A new structure for PM brushed DC motors and a novel algorithm for its design has been developed.

Terminal Terthiophenediones: Fast-Decay Fluorescent Dyes and Their Efficient Syntheses.

Terminally acylated terthiophenes, in particular, the bis-pivaloyl derivative, were synthesized by Friedel–Crafts acylation with sub-stoichiometric amounts of standard zinc oxide and exhibit strong fluorescence and an ultrafast fluorescence decay of 400 ps. Their high photostability and large Stokes’ shifts are good prerequisites for applications in optical GBit fast data systems such as fiber optics in slip rings.

Dynamic modelling methodology for an HTS energy converter using moving mesh

Lots of high-temperature superconducting (HTS) devices which require current leads, slip rings or brushes have to face the challenges such as large heat load and complex structure. Recently, an HTS energy converter has been proposed, which can not only induce but also exploit persistent current in a closed HTS ring, realizing the conversion of mechanical energy—electromagnetic energy—mechanical energy wirelessly. In this work, a dynamic modelling method based on the H-formulation and moving mesh has been proposed to accurately simulate the electromagnetic performance of the HTS energy converter. The proposed modelling method can depict the induced current density inside the superconductor and magnetic field distribution, serving as a powerful tool to analyze the complex working principle of the HTS energy converter. The validity of the model has been verified by experimental results. Besides, effects of different parameters of the energy converter have been investigated in detail by our proposed model, to provide further insight into the design and applications of the device.

Disturbance mechanism of the solar array drive system on spacecraft

An electromechanical dynamic model of the solar array drive system (SADS) was proposed to analyze the disturbance characteristics, and verified by the experiment study in the laboratory. The factors which directly cause the SADS’s disturbance were differentiated based on the idea of reductionism, and corresponding disturbance characteristics were investigated. The other kinds of factors which do not cause disturbances but affect the disturbance characteristics of SADS, as well as their influence rules, were also analyzed. The results of the proposed model agree well with the experimental data, with an error of less than 10%. Disturbances of SADS occur when the rotational-motion acceleration and structural-vibration acceleration are not both equal to zero. The current subdivision of the drive controller, nonlinear magnetic field of the stepping motor, and the varying meshing parameters of the gear reducer can directly cause disturbances, which vary periodically and occur near excitation frequencies and high-order harmonic frequencies. The amplitude of the disturbance increases with a decrease in the number of current subdivisions, an increase in electromagnetic excitation and the fluctuation margin of gear-meshing parameters. The closed-loop current control, nonlinear friction between the brush and slip ring, the bending-torsional coupling of the solar array, and the gear clearance of the gear reducer do not cause the SADS’s disturbances but can affect their profile and spectrum distribution from different aspects, even introducing disturbance components in the non-driving directions.

Epistemic uncertainty quantification via uncertainty theory in the reliability evaluation of a system with failure Trigger effect

Reliability evaluation of system with dependent failure processes is a problem that draws more research attention. It is essential to quantify the epistemic uncertainty in the system for high evaluation accuracy. Trigger is one of the typical dependent failure processes. Trigger effect indicates that some events occur because of the trigger of other events. This paper studies the epistemic uncertainties in the reliability evaluation of the system with trigger effect based on uncertainty theory. The model-form uncertainty of physics of failure (PoF) model, the failure process uncertainty due to lack of knowledge and the propagation of them in the system are quantified with Belief Adjustment Factors Method (BAFM) and the Liu process. System belief reliability is evaluated by decoupling the correlations between the trigger failure mechanism and triggered failure mechanisms. A conductive slip ring in electromechanical orientation device is introduced as a case. The trigger effect and system belief reliability are analyzed. Results show that, compared with probability method, evaluation values with uncertainty method are more conservative and stable in the case..

Dynamic response enhancement of BDFIG using vector control scheme based internal model c ontrol

Doublefed induction generator(DFIG) has shown tremendous success inwind turbines due to its flexibility and ability to regulate the active andreactive power. However, the presence of brushes and slip rings affects itsreliability, stability, and power quality. Furthermore, itdoes not providepromising outcomes in case of faults even in presence of the crowbar circuit.In contrast, thebrushless doubly fed induction generator(BDFIG) is a morereliable option for wind turbines than its mentioned counterpart due to theabsence of the brushes and slip rings. This research work as such attempts toimprove the dynamic performance of thevector control(VC)oriented powerwinding (PW) stator flux-based BDFIG by optimally selecting theproportional-integral(PI) gains throughinternalmodel control(IMC)approach. The proposed control scheme is utilized to regulate the speed,torque, and reactive power of the considered BDFIG independently. Contraryto the previous literature where the “trial and error method” is generallyutilized, the current research work uses the IMC for selecting the mostsuitable PI parameters, thus reduces the complexity, time consumption, anduncertainty in optimal selection. The considered BDFIG based wind turbinewith the proposed control scheme provides a better BDFIG control designwith an enhanced dynamic response as compared to that of the same withDFIG under identical operating conditions and system configurations.

Study on dynamic sealing performance of combined sealing structure of telescopic type of downhole robot by using HTHP coupling method.

The sealing performance will directly affect the operation of downhole robot under HTHP condition. Traditional analysis methods of sealing performance are that the temperature and pressure is loaded respectively. This can not really evaluate the sealing performance. Besides, the simulation process is: Step 1: pre-compress O-ring to produce contact force. According to the contact pressure, select the compression ratio to calculate the displacement of the slip ring. Step 2: load fluid pressure on the O-ring. This simulation method is to directly load pressure on the undeformed O-ring. However, the O-ring will deform after pre-compression. Therefore, this simulation method is not accurate. In order to make the simulation data more accurate, calculate the data of shape, stress, and strain of O-ring caused by pre-compression caused by assembly. Then, import the deformation body containing the real data of shape, stress, and strain into a new model. On the basis, establish the numerical simulation model of piston, piston guide rod, O-ring, and FTS-ring with HTHP loads is. Finally, calculate and analyze. When the compression ratio of the O-ring is about 14%, the sealing performance is good. What's more, the distribution of contact stress and Von Mises of the O-ring at 8.3 mm/s of motion speed are analyzed. The results show that the foot shaped combined sealing structure can keep a good dynamic sealing performance under HTHP condition. This paper provides a theoretical basis for the analysis of the dynamic sealing performance by using HTHP coupling method. In the analysis of sealing performance: the hydraulic pressure is loaded to the real model with the real shape, stress, and strain produced by the O-ring assembly. This can more accurately evaluate the sealing performance under HTHP condition. It also provides a reference for the dynamic sealing structure design of downhole tools.

Dynamic Performance Analysis of a Grid-Connected Doubly-Fed Induction Generator

In the field of wind energy, the doubly fed induction generator (DFIG) is commonly used in variable speed wind energy conversion systems (WECS). This paper presents a review of various topologies, configurations, power converters and control schemes used with the operation of the DFIG. The operation of DFIG based on both slip ring and brushless arrangement has been discussed. The grid integration of DFIG and its influence on system stability, system reliability, power quality and power transmission is reviewed.

Rotational Piezoelectric Energy Harvesting: A Comprehensive Review on Excitation Elements, Designs, and Performances

Rotational Piezoelectric Energy Harvesting (RPZTEH) is widely used due to mechanical rotational input power availability in industrial and natural environments. This paper reviews the recent studies and research in RPZTEH based on its excitation elements and design and their influence on performance. It presents different groups for comparison according to their mechanical inputs and applications, such as fluid (air or water) movement, human motion, rotational vehicle tires, and other rotational operational principal including gears. The work emphasises the discussion of different types of excitations elements, such as mass weight, magnetic force, gravity force, centrifugal force, gears teeth, and impact force, to show their effect on enhancing output power. It revealed that a small compact design with the use of magnetic, gravity, and centrifugal forces as excitation elements and a fixed piezoelectric to avoid a slip ring had a good influence on output power optimisation. One of the interesting designs that future works should focus on is using gear for frequency up-conversion to enhance output power density and keep the design simple and compact.

An innovative torsional vibration absorber of vehicle powertrain system: Prototype design, performance test, and control experiment

A dynamic vibration absorber can effectively reduce the vibration of a mechanical system, and designing a new type of torsional vibration absorber to reduce the torsional vibration of the vehicle powertrain system and establishing relevant experiments to test its vibration reduction performance are necessary. This article presents a detailed design and manufacturing process of an innovative torsional vibration absorber with magnetorheological elastomers (MREs) as its core intelligent element. A series of experiments are carried out to evaluate the vibration reduction performance of the new vibration absorber. A vibration reduction performance experiment with a torsional vibration exciter is used to test the vibration transmissibility of the vibration absorber, and the frequency shift range is identified. An engine vibration reduction performance experiment is carried out to verify the feasibility of the vibration absorber in actual powertrain systems, and its good vibration reduction effect is also proven by comparative experiments. A semi-active control experiment of the vibration absorber is performed to verify the reliability of the programmable power supply and the conductive slip ring and prove the effectiveness of the dominant external excitation frequency identification method and vibration absorber control strategy.