Carbon Brush Wear Research Articles

Carbon brush wear calculation in marine environment based on temperature field analysis

In the marine environment, the working environment of the doubly fed wind generator carbon brush and slip-ring system is complicated, salt spray deposits and seawater erosion affect the temperature field and contact surface friction factor leading to carbon brush wear increase and shortened replacement cycle. The three-dimensional temperature field simulation model of the carbon brush and slip-ring system is established. The main factors affecting the carbon brush and slip-ring system temperature field are sliding velocity, load current, ambient temperature, contact surface condition and contact pressure applied to the brush. Wear capacity of carbon brushes is affected by contact surface temperature. An experimental platform combined with the salt spray test machine was built to carry out the contact current, contact pressure, salt spray concentration and experimental temperature experiment. The improved Coulomb-viscous friction force model was used for the wear prediction model. The sliding velocity, contact pressure, contact current, experimental temperature and salt spray concentration were introduced into the model. The experimental verification has shown that the prediction model can effectively predict the carbon brush wearing capacity under different conditions. This model can be applied to formulating the carbon brush wear amount and replacement cycle in the marine environment reducing operation and maintenance costs.

Development of sliding contact resistance testing equipment for carbon brush confluence ring

A carbon brush and a confluence ring form a pair of sliding electrical contacts. To reduce the contact resistance between the carbon brush and the confluence ring, the time for the running-in wear of the carbon brush increased during the machining process to increase the actual contact area. As a result, the welding and ablation failure between the carbon brush and the confluence ring happened under the impact of high current during service. To explore the effect of carbon brush wear on sliding electrical contact performance, it is necessary to monitor the dynamic contact resistance of the carbon brush and the confluence ring. In this paper, a set of 8-channel contact resistance testing equipment is developed. The device uses a relay array to achieve 1-8 channel gating and uses a data acquisition card to detect the contact resistance of each carbon brush and confluence ring pair combining with a four-point method. Based on the Labview software, it realizes the selection of acquisition channels, data acquisition card driving, real-time data processing, displaying, and storage. The range of contact resistance that this set of equipment can detect is 10mΩ ∼2Ω, and the accuracy can reach 1% of the full scale. Finally, the simulation experiments show that the testing equipment meets the technical requirements, and the continuous test runs stably and reliably. It can be used for the testing and research of the sliding contact resistance between the carbon brush and the confluence ring during the running-in wear process.

Analysis of Factors Affecting the Working Performance of Brush slip ring system in Special Environment

In the marine environment, the wear of carbon brushes in the brush slip ring system of doubly-fed generators is accelerated and the replacement frequency is relatively high. In this paper, an experimental platform is built to simulate the working environment of the carbon brush slip ring system in the marine environment, and the factors causing the accelerated wear of carbon brushes are explored, so as to make suggestions on operation and maintenance of the brush slip ring system. The composition of the oxidation film on the contact surface of the brush slip ring has been quantitatively analyzed to provide a basis for determining the content of the oxidation film.

Research on Fault Risk Identification and Control of CT Simulator Based on FMEA

To explore the high-risk fault risk of CT simulator and the main causes of the risk, and to put forward effective risk management strategies. The failure mode and effect analysis method was used to identify and control the operational fault risk of CT simulator. 5 major fault components, 8 fault failure models and 17 failure causes were analyzed. The top 5 failure causes are:anode target surface burn caused by direct scanning without warming up the tube (590.4), tube failure (518.2), burnout of joints caused by aging of high voltage cables (424.2), motor carbon brush wear (304.8) and belt break (296.4). The failure mode and effect analysis method can effectively identify the risk of equipment failure, and thus specifically formulate risk management and control measures to ensure the normal operation of equipment and the safety of doctors and patients.

Prediction of vacuum cleaner motor brush life: a regression approach

The main focus of this paper is the empirical modelling of the wear of carbon brushes. Rather than determining the dominant wear mechanisms, an approach towards the prediction of wear under a range of different conditions was used. The models were obtained by multiple regression analysis using lifetime (LT) data contributed by the biggest European manufacturer of vacuum cleaner motors. This included reliability data for 607 different test populations involving 3980 motors. Exploration of the data revealed that wear-out parameters behaved in accordance with the existing field theory, giving additional confidence to the models. The numerical appreciation of the wear-out parameters and the resulting conclusions will be beneficial to motor design and reliability engineers. Learned knowledge will be used for faster selection of optimal design and operational motor parameters to meet recent EU regulation 666/2013. Along with the more rapid design of the product, a reduced number of LT tests will result in significant energy savings.

Carbon Brush Wear of Radar Tachometer Identification Technology Based on Eigen Value Analysis in Time Domain

A new type of tachometer carbon brush wear detection technology is proposed based on data acquisition and signal processing technology, the key of which is that the tachometer carbon brush output information is acquired and processed, moreover, the real time conditions of the carbon brush wear are detected and analyzed based on the time domain Eigen value analysis method. During the data processing process, the results of the dimensional parameter processing method are compared with the results of the dimensionless parameter processing method at the same time. Then, we find that the detecting precision is greatly promoted and measurement probability is guaranteed by reasonable threshold selection. Experimental results indicate that the technology proposed here has high stability, high reliability, and high detecting probability, which has great practical value and deserves being extended widely.

Apparatus to measure chemical wear of carbon brushes

It has been inferred for several years that the wear of a carbon brush at a sliding interface of a dc machine is influenced by chemical factors. Previously, the difficulties of isolating and measuring chemical factors in such circumstances have discouraged specific verification. An apparatus is described that hermetically seals a selected polarity brush and uses an artificial atmosphere of humidified oxygen and argon to simulate air. By monitoring the ratio of mass spectrometric peaks of CO+2 to 36Ar+, a consistent rise is observed in the amount of CO2 present. The amount of carbon thus gasified exceeded 25% of the total carbon lost.

Electron spectroscopy analysis of contact surfaces in the wear of carbon brushes against copper commutators

Carbon brushes and copper commutator strips have been analyzed by a combination of techniques to investigate possible surface-related phenomena in the excessive wear of carbon brushes in motors and generators. X-ray photoelectron spectroscopy, scanning Auger microscopy, optical microscopy, scanning electron microscopy, and energy-dispersive X-ray analysis were used in this study. A thin SiO 2 film, of the order of 30 Å on the brushes, and of the order of several hundred Å on the commutators, was correlated with high wear and is believed to be the chief cause of the excessive wear. Possible models for the effect of SiO 2 on carbon brush wear are discussed.

189. Chemical aspects of carbon brush wear

189. Chemical aspects of carbon brush wear

Chemical factors in carbon brush wear

Chemical factors involved in the wear of carbon brushes on metal slip rings are discussed. Under conditions of elevated temperature operation in an oxidizing atmosphere, a correlation is found between the oxidation characteristics and the wear rates of carbon brushes. It is demonstrated that temperatures in the oxidation range can readily be generated by current converging through high resistance constrictions in the contact zone. Copper and other metals present in the slip ring can act as catalysts for the oxidation, the metal oxide particles migrating into the interior of the brush and causing enhanced gasification rates and increased porosity. Treatment of the brush with oxidation inhibitors, such as phosphorus oxychloride, and surface alloying of the ring with non-catalytic materials, such as zinc, can reduce the wear rate at elevated temperatures under favorable conditions. Graphite surfaces are also attacked by reactive gaseous species such as atomic nitrogen and oxygen, ozone and nitrogen oxides which may form near the brush surface during arcing.

Closure to “Discussion of ‘Studies in Boundary Lubrication—III: The Wear of Carbon Brushes in Dry Atmospheres’” (1948, Trans. ASME, 70, pp. 497–498)

Closure to “Discussion of ‘Studies in Boundary Lubrication—III: The Wear of Carbon Brushes in Dry Atmospheres’” (1948, Trans. ASME, 70, pp. 497–498)