Slip Ring Assembly Research Articles

Optimized Design of Slip Ring Assembly for Aerospace to Reduce Deep Dielectric Charging

The deep dielectric charging of the slip ring assembly caused by high-energy electron radiation leads to the failure of the solar array drive assembly (SADA), which accelerates the failure of the whole satellite. It is necessary to optimize the structure of the slip ring assembly according to the deep dielectric charging characteristics to reduce the risk of discharge accidents. In this article, based on the law of current conservation, a 3-D simulation model for deep charging of slip ring assembly is established by combining Geant4 with COMSOL. Under the FLUMIC3 electron radiation environment, the essential characteristics of the electric field and potential distributions in the slip ring assembly are studied. Based on these, optimization schemes for aluminum shielding structures, insulation baffles, and ground structures are proposed. The simulation results show that the simultaneous use of the three proposed optimization schemes can significantly reduce the electric field distortion caused by high-energy electron radiation, and the maximum reduction is about 70%. At the same time, the overall quality of the aluminum shield and the basic structure of the slip ring assembly can be maintained. It provides specific references for the actual design of slip ring assembly in SADA.

Unified analysis and output estimation for strong coupling contactless slipring system

Contactless slipring (CS) system utilizing inductive-power-transfer (IPT) technology is a good candidate for the traditional mechanical slipring assemblies. However, suffering from the high harmonic currents in strong coupling CS system, the output power will deviate from the theoretical values estimated by the fundamental harmonic approximation (FHA) and its extension method, i.e., E-FHA, in which the power are transferred by both the fundamental current and the high order harmonic currents. In order to achieve high precise output estimation, a unified analysis is proposed in this paper. Firstly, Fundamental-harmonic Double Resonance Phenomenon is revealed via impedance analysis, to address the nature of the high harmonic currents in strong coupling system. Then, a unified output current expression owning high precision is derived, followed by a unified fundamental load impedance. Discussions show that both the output and the fundamental load impedance of FHA, and E-FHA are all the special cases of the unified expressions proposed. FHA, and E-FHA are precise enough for the loose coupling system, whereas the proposed method is indispensable for the strong coupling system with k>0.4. Finally, simulations and experimental measurements of a 1.6kW CS system, as well as the comparative studies among FHA, E-FHA, and the proposed method, are presented, indicating that the proposed method are effective for high precise output estimation.

Slip Ring Test Assembly With Increased Breakdown Voltage Limit for High-Voltage Bus Satellites

In this article, a setup including a passive gas breakdown mitigation technique for satellite slip ring assemblies (SRAs) is introduced and tested. The setup features a central conducting ring, separated from two external conducting limiting discs (LDs) by insulating rings. The characteristic breakdown curves are measured as a function of the surrounding pressure by biasing the central ring and setting the LDs at a variable voltage. The minimum breakdown voltage is increased from ~420 to ~860 V by biasing the LDs at one half of the voltage applied to the central ring. This solution is further applied on a test-SRA that includes the main features of a standard cylindrical SRA: a stack of conducting rings on which conducting brushes slip to ensure the electrical contact between moving components. The minimum of the breakdown curve is raised from ~400 V for the grounded LDs to ~600 V for the passively biased LDs. This result confirms the possibility to improve SRA protection for the entire pressure range encountered by a satellite during its operational life, from atmospheric pressure to in-orbit high-vacuum, meeting the requirements for the next generation of satellites.

Wireless stress sensor based on piezoelectric energy harvesting for a rotating shaft

A shaft is a mechanical component which transmits mechanical power and torque. A failure of the shaft may result in serious damage to machine in operation. Contact or noncontact monitoring techniques of rotating shaft have been developed in order to prevent this damage. The application of contact monitoring techniques requires the use of additional devices. First of all, a slip ring assembly, which enables a sensor supply and a sending of measurement data from a rotating shaft to some receivers. The use of the slip ring assembly, which requires an access to the front of the rotating shaft and an additional channel located in an inside of this shaft, are the most important weaknesses of contact techniques. In contrast to these approaches, the article presents a contact technique of stress monitoring in the rotating shaft, in which the slip ring assembly is not required. Presented contact technique consists of a wireless sensor based on piezoelectric energy harvester and a radio transmission system. The piezoelectric energy harvester consists of Macro Fiber Composite (MFC) patch and a system of energy storage and energy transfer control. MFC patch is directly glued to the rotating shaft surface and product an amount of electric energy which is enough to supply only a radio transmitter. Such built wireless sensor based on piezoelectric energy harvester was tested in laboratory stand which contained a rotating shaft with a system of force generation, a belt transmission with a system of generation of rotational motion, and a measurement system. The time between radio signals was measured for selected values of the rate of rotation of the shaft and for selected values of stress in the shaft in laboratory experiments. The experiments showed that dependence between the value of stress in the shaft and the number of radio signals per second can be approximated by a straight line. A method of measurement of stress in the rotating shaft was elaborated on the basis of the experiments. The method is based on the number of radio signals per second, which is linearly correlated with an average value of stress in the shaft, for the known value of the rate of rotation of the monitored shaft. The elaborated piezoelectric wireless sensor of stress were tested as a main part of sensor of cracks in the shaft surface in the last experiments. The time, after which the crack was detected, depended on a sampling period of such piezoelectric wireless sensor. The sampling period in turn depended on the three parameters: an average value of stress in a place where MFC patch is glued, the rate of rotation of shaft, a capacity of capacitor in a system of energy storage in a piezoelectric energy harvester.

A Novel Dual-Rotor Bidirectional Flux-Modulation PM Generator for Stand-Alone DC Power Supply

A novel bidirectional flux-modulation permanent magnet (BFMPM) machine for stand-alone dc wind power generation is proposed in this paper. The key is to control the inner rotor position with a small servo motor, and with the bidirectional flux-modulation effect, the resultant induced voltages in two sets of stator windings can be adjusted accordingly. Consequently, in a wide wind speed range, the various-speed constant-amplitude-voltage operation is realized. The novel structure has two major merits. First, it has high reliability without the maintenance problems caused by mechanical gearboxes, slip ring assembly, and brushes. Second, the proposed system requires a low-cost uncontrolled diode rectifier, which enhances the reliability and reduces the cost of the system. The analytical model and operation principle of the BFMPM machine are illustrated and the simulation results using a finite-element method is presented. A prototype is optimized and fabricated. The experimental results agree well with the simulation results and verify the correctness of the analytical model and the effectiveness of the proposed structure. Therefore, the novel structure offers a potential solution to provide a stable dc power for the standalone condition, such as remote area and offshore island.

Gas breakdown mitigation in satellite slip rings

Direct current (DC) gas breakdown is experimentally investigated for high-voltage circular conductors and insulators that reproduce the main features of a satellite slip ring. Breakdown voltages are measured in the pressure range 10−3–10 mbar, where gas breakdown is predominant with respect to vacuum breakdown. The measured breakdown curves show clear similarities with Paschen's curve, which is generally associated with parallel plate electrodes. It is shown that the low-pressure branch of the measured curves is determined by breakdown between the high-voltage ring and the grounded vacuum chamber, whereas the high-pressure branch is due to discharges between the high-voltage ring and the adjacent grounded rings. A technical solution is introduced to inhibit the gas discharges at low-pressures in a slip ring assembly: The diameter of the grounded conducting discs is extended, strongly increasing the measured breakdown voltages by modifying the electric field distribution. The safe operating pressure range of the satellite slip ring is thereby increased by two orders of magnitude.

Consequent-Pole Hybrid Brushless Wound-Rotor Synchronous Machine

Several brushless topologies for wound rotor synchronous machines (WRSMs) have been presented in recent years to replace the brushes and slip-ring assembly in conventional WRSMs [1–4]. The brushless operation of the WRSM presents these machines as an alternative to the permanent magnet synchronous machines (PMSMs) because of their low cost and competitive performance as compared to the PMSMs. However, the drawback of the brushless wound rotor synchronous machines (BL-WRSMs) is their low starting torque because of the absence of the excitation source on their rotor. Although, the BL-WRSM achieves the rated torque at the base speed but low starting torque under the base speed makes these machines less suitable for variable speed applications. A PM assisted BL-WRSM was presented in [5] to overcome the problem of the low starting torque and to provide better performance under full-load conditions. However, the presence of the PM on each pole increases the cost of the machine. Moreover, the leakage flux is increased in PM assisted machines. These issues can be resolved by the consequent pole (CP) machines [6]. In this paper, a consequent pole hybrid brushless wound rotor synchronous machine (CPH-BLWRSM) is proposed to overcome the problem of low starting torque, and to reduce the PM usage as compared to the PM assisted machines. A 2-D finite element analysis is performed to validate the proposed CPH-BL-WRSM and its performance is compared with the existing BL-WRSM and PM assisted BL-WRSM.

Influence of contact parameters on the tribological behaviour of various graphite/graphite sliding electrical contacts

Sliding electrical contacts are used in devices for the conduction of electrical power or the electrical signals between stationary and moving parts. The most widely used electrical-sliding system is still the conventional slip ring and brush assembly. In the last decade, the lifetime of ring-brush contacts was extended through the use of better contact-material combinations and design improvements. However, the extremely rapid electrification of many more components has put severe demands on this extended lifetime. This paper presents a novel, patented design for two sliding discs that allows the use of advantageous graphite/graphite contacts. In the literature there is a serious lack of understanding the performance of sliding electrical contacts with graphite/graphite pairs, which depends on the key contact parameters, as well as the influence and potential of the different available graphite materials. The normal load, the contact velocity, the electric current, and the three self-mated graphite contacts, i.e., hard carbon, electrographite and polymer-bonded graphite, were investigated. The results indicate that the contact conditions influence the performance, which is also very dependent on the graphite materials. The polymer-bonded graphite showed the best results in this study.

Wear and electrical performance of a slip-ring system with silver–graphite in continuous sliding against PVD coated wires

Sliding electrical contacts transferring current between stationary and rotating components are also tribological systems. Although low contact resistance and noise are prioritised, lower wear rates reduce material usage, and lower friction reduce energy loss. In this paper a slip-ring assembly with wires contacting a silver–graphite ring is investigated with the aim to optimize the wire material to displace all wear to the ring. Uncoated wires and wires coated with nanocomposite Ti–Ni–C or TiN are tested at 100mA current. Tribofilms, consisting mainly of silver and carbon, form on the wires and a contact resistance of around 0.5Ω is measured for all wire materials. The properties of the tribofilms control the overall performance and the similarity between them, regardless of wire material, is the reason for the similar contact resistance. The Ti–Ni–C coating wear least on the silver–graphite. Both coatings degrade and wear off during testing, exposing the steel substrate. The steel itself also wears, although not at a rate excluding it as a possible wire material. None of the three surfaces fully displaces wear to the ring only. Considering the performance of the uncoated steel wire, coatings cannot be motivated on behalf of either improved electrical performance or wire protection.

Through-Hole Contactless Slipring System Based on Rotating Magnetic Field for Rotary Applications

Contactless slipring system based on inductive power transfer is a preferable alternative to mechanical slipring assemblies. They are designed to deliver required output power to a rotary shaft without direct electrical contacts. The current single or multiple-unit through-hole single-phase systems often have limited power transfer capability within a confined physical space; thus, they may not be able to meet the load requirement for certain applications such as wind power pitch control. This paper presents an integrated polyphase through-hole contactless slipring system by generating a rotating primary magnetic field coupled with balanced power pickups at the secondary side with zero mechanical driving torque on the shaft. A new index termed “mutual inductance per pole” is introduced to simplify the analysis of the mutually coupled polyphase system to a single-phase basis. Simulation and practical experiments have demonstrated that, with the same physical size, the proposed contactless slipring setup can transfer 55% more power compared with the existing single-phase counterpart.

Fiber-Optics Data Transmission for a Gyro Stabilized Platform

An optical fiber based data transmission link for a four-axis gyro stabilized inertial reference system is presented. The operation and configuration of the gyro stabilized platform is introduced to explain the requirement of data transmission. Four passive fiber optic rotary joints (FORJs) instead of traditional electrical sliprings are used to transmit optical signals between these relatively rotating gimbals. The hardware and software design of this optical fiber communication system operated at an updating rate of 1kHz are described to achieve high-speed, real-time, reliable data transmission. The experimental results show that the fiber optic rotary joint-based data transmission link is real-time and reliable. The use of FORJs as fiber optic sliprings will also result in an extremely low friction torque by comparing to electrical slipring assemblies. This allows the system designer to optimize the servo control performance for such high-precision gyro stabilized inertial reference systems.

An Improved Design of 3D Swept-Volume Volumetric Display

In this paper, we present a new design of a swept-volume 3D-360-degree display system with rotating LED panel. This system, which adopts the idea of modular design, is constituted of a mechanical part, a circuit part and a software part. The circuit part is mainly composed of synchronous control module, high speed data transmission module, display module and display control module, etc. The mechanical part includes a mounting platform, a carbon brush assembly, a slip ring assembly, a power mechanism, a synchronous belt mechanism, a rotation assembly, a top cover pressing mechanism, and an auxiliary support. The software part mainly realizes the 3D image data generation, simulation, transmission and display control function. The experimental results show that the SV3DD (swept volume 3D display) system can display 3D images and animations with 360-degree view angles.

Systems and Methods for Reducing Noise in an Imaging Catheter System

The present invention provides systems and methods for reducing noise in an imaging catheter system. In an embodiment, a catheter comprises an imaging transducer and a transmission line within the catheter to transmit signals to and from the transducer. To reduce noise caused by exposure of the transmission line to external interference, a choke balun is coupled to the transmission line. In another embodiment, the signal from a rotating imaging transducer of the catheter is coupled to a motor drive unit by a slip ring assembly. The transducer signal is passed through first and second transformers placed on opposite sides of the slip ring assembly to reduce noise from the slip ring assembly. In another embodiment, the catheter includes a position sensor to track the position of the catheter. The position sensor is coupled to a second choke balun to further reduce noise.

COMPARATIVE STUDY OF WIRELESS VERSUS STANDARD THERMOCOUPLES FOR DATA GATHERING AND ANALYSES IN ROTARY COOKERS

ABSTRACT The performance of a wireless temperature sensor was compared with that of a conventional thermocouple for gathering heat penetration data. A central composite rotatable design experimental design with three different processing conditions (glycerin concentration [70–100%], retort temperature [111.6–128.4C] and retort speed [4–24 rpm]) were employed using 307 × 409 cans containing the particulate fluid to compare the performance of the two devices. Experiments were performed in a fixed axial mode of rotation in a rotary cooker, and only liquid temperature was measured using both temperature sensors. The heating rate index, fh, cook value to lethality ratio, CO/FO, were evaluated and compared using a t-test. Statistically there were no differences (P > 0.05) in the performance of the two systems with respect to the parameters tested; however, compared with conventional thermocouples, the wireless sensors were more stable, and more practical for use in rotary cookers especially for free axially rotating cans. PRACTICAL APPLICATIONS In order to meet the recent industrial demand to optimize the thermal process in rotary cookers, it is imperative that time-temperature data during processing be accurately gathered. To gather temperature data in rotary retorts, standard thermocouples equipped with a slip ring assembly are used together with a data acquisition set up. A biaxially rotating can, as in continuous cooker simulators, would require two such slip rings: one at the can level and one at the retort level, making the data gathering more cumbersome. To assist in such scenarios, use of self-contained “wireless” sensors is more practical. This study focuses on concerns about using wireless sensors due to their own volume influencing the temperature measurement at the critical control point. This study will demonstrate that wireless sensors could potentially replace standard thermocouples for the measurement of temperature for convection-heated food in large size 307 × 409 cans.

An experimental assessment of lawnmower blade loading

An experimental study of the loading to which a lawnmower blade is subjected during normal operation has been performed. The blade of a consumer-grade walk-behind electric lawnmower was instrumented with strain gauge bridges and strain data were collected using a slip ring assembly and personal-computer-based data acquisition system with integral amplifier. Blade strains were monitored over a range of grass-cutting conditions. It was found that blade strain was dependent principally upon the rotational speed, with no perceptible effect due to cutting conditions, other than the indirect effect due to blade speed changes. The measured strains also compared well with calculated strains, particularly at low speeds. At higher speeds, there were small differences between measured and calculated strains and these differences are attributed to the effects of blade deflection. The results of this study suggest that blade stresses can be accurately calculated using models which include only the effects of rotation. Relative to other possible types of loading (i.e. aerodynamic and grass impacts), rotational effects are easily modelled. At higher speeds, models should include the effects of large-displacement non-linearities to account for the effects of blade deflection. These findings will enable engineers and designers to perform analyses that will minimize the repetitive and often extended empirical testing in arriving at a final mower blade design. Where empirical testing is required, these results indicate that such testing should be based on blade rotation rather than on static fixtures in which cyclic deflection of the blade is applied.

Brush/slip ring current collector performance and anomalies during compulsator commissioning

During recent tests associated with a model scale compulsator development program at The University of Texas at Austin Center for Electromechanics (UT-CEM), the performance of severe duty trailing arm brush current collectors was evaluated. The original material of choice for the brush slip ring design was 70075-T6 aluminum to minimize machine mass and simplify slip ring assembly on the rotor shaft. The slip rings have a nominal diameter of 5.5 in. The combination of CM1S copper, trailing arm brushes, and aluminum slip rings performed well up to about 80% full speed, although the design did not appear to be very damage tolerant. As testing continued at higher speeds, one of the slip rings began to exhibit small shallow arc pits in the brush track on the slip ring outer diameter. This was observed on only one slip ring and had no apparent affect on machine performance. Left unchecked, this shallow arc damage can cause a high speed brush to "bounce" excessively during a run and cause more severe damage, as well as increase the circuit impedance from the arcing. This paper presents a general description of the observed brush performance during normal and fault conditions. It also includes a description of mechanical analysis and field strength measurements done around the brushes in an effort to explain the "one brush" bouncing. Brush and slip ring design upgrades (including a reinforced brush actuator for increased brush down-force and a newly implemented two-layer aluminum and steel slip ring design) are discussed.

New modular slip-ring assembly can match your needs

New modular slip-ring assembly can match your needs

Experimental study of the stress distribution in the spokes of bare filament flywheels

A bare filament quasi-circular flywheel has been instrumented with strain gauges and the strains in the spokes measured using a slip-ring assembly to transfer the signal from the strain gauges to the stator of the machine. The results are compared with theoretical results obtained using a mathematical model described in previous papers. The results of some temperature measurements, aimed at defining possible test procedures rather than evaluating the temperature field of the flywheel, are also presented. The influence of the results obtained on the design of such highly loaded structures is discussed.

Reduction of Particle Growth Rate and Slip-Ring Assembly Segmented Rings

A study was conducted to determine a method of reducing particle growth rate between slip-ring assembly (SRA) brushes and segmented rings. The particles from the SRA were analyzed using a scanning electron microscope (SEM) to determine the formation mechanism. An X-ray fluorescence analysis of the particle revealed its material composition. Three approaches were then considered as the most likely to alter the growth rate: burnishing the conductive segments, altering the quantity of lubricant on the segmented rings, and modifying the brush forces. The materials, tools, and techniques for these three approaches were developed in conjunction with weighing the advisability of pursuing each approach to reduce the particle growth rate. After the reduced brush-force approach had been selected, a time-lapse 16-mm movie film was made of particle development over five days at 1 frame/min for 317 000 slip-ring revolutions. The film compares growth rates of brush and ring groups set at preselected brush-force ranges. The segmented-ring brush-force range was thereby determined; then SRA's were modified and retested, with positive results.

Gas filled high voltage slip ring assembly : N E Lewis, assigned to Litton Systems Inc

Gas filled high voltage slip ring assembly : N E Lewis, assigned to Litton Systems Inc