Fiber Slip Ring accounts for almost 10 percent of overall motor Slip Ring in the market that just needs a small amount of maintenance. And, almost 60 percent of Slip Rings, as conductive component, are composed of composite metal brush and are generally sintered by metal and graphite. Even through the fact that those slip rings with composite metal brush are processed with its service life of 7500 million rotations manufactured by its supplier, they also need to be frequently maintained. The rest of 30 percent of the motor slip ring adopts single-wire precious metal brush (generally manufactured by the gold). The amount of regular maintenance for the slip ring with composite metal brush and with single-wire brush is much larger than that of fiber slip ring.
The reason is that the design for composite brush is preferentially wearing its brush to avoid its slip ring wear. And, its brush needs to be long enough to prolong its brush replacement cycle with a large extent. In the field of high power or high reliability for slip ring, that material is faced to three-aspect challenge:
1) In the process of its operating, abrasive dust need to be regularly cleaned because the dust is powdery, conductive and abrasive.
2) The brush material is sensitive for the humidity. If relative humidity is lower than 15% or higher than 85%, its material will be wore unbalanced.
3) In the field of signal-level circuit, these composite brushes will occupied larger amounts of the space.
Compared to that of slip ring with composite brush, the design advantages for the slip ring with single-wire metal brush are less amount of abrasive dust and higher capacities for its signal circuit as well. But, the system of single-wire metal brush also exists the following defects:
1) smaller size of single brush is lack of sufficient conduction capacity.
2) For example: most of contact point between the gold needs related lubrication. But, it sis difficult to keep a long-lasting and adequate lubrication.
Presently, new-fashioned design for slip ring begins to adopts graphite or metal brush and its signal circuit is designed for the slip ring with golden single-wire brush. In the field of lower rotations for its slip ring assembly, the "mixed application" can meet the requirements. But, in the field of the same assembly, the brush with the "mixture of the graphite and the metal" and the style with "the-golden-contact-the-golden" will reduce its motor operating reliability. The graphite/the metal abrasive dust will pollute its golden signal contact and generate abrasive metal powder, especially in the process of its contact-point lubrication; its signal circuit will be prematurely ineffectively.
The design for fiber brush is that lots of metal fiber wires is tied up compact multi-fiber "brush". Generally, these fibers are equivalent to single-wire designed precious metal materials. Moreover, the slip ring in the process of brush operating will also be coated precious metal. The usage of precious metal will prevent the generation for the oxide and coverage layer, ensuring extremely small amount of contact force. Small amount of contact force increases the speed of the wear, therefore abrasive dust generated by the brush can be almost ignored. Furthermore, multiple metal fibers can provide excellent electroconductibility and higher ampere density. Therefore, the engineer can apply the above-mentioned in the field of power circuit and signal circuit as well.
