Patent Application
20210057860
It is well known that electrical slip rings are electromechanical devices that consist of rotational (rotors) and stationary (stators) members. They allow the transmission of electrical signals and power from their rotors to stators or vise verse.
The present invention relates generally to an electrical slip ring, and more particularly if the rotational speed between said rotational (rotors) and stationary (stators) members is very high (up to 60000 rpm).
A conventional electrical slip ring consists of conductive rings and brushes. Said rings are mounted on said rotor and insulated from it. Said brushes are usually fixed on said stators and run in contact with said rings, rubbing against the peripheral surfaces of the rings, transferring electrical power or signals to the stator side.
Modern metal fiber brush technology offers significant improvement over traditional carbon brushes in both data and power transmissions, offering extended brush and slip ring service life, high current capacity, and significant decreases in service acoustics and electrical noise. The fiber brushes are multiple of hair-thin metal filaments which on one end are collimated by and terminated into a metal tube, while another free, un-terminated end runs in contact on the ring surface. However, the sliding contact between the rings and brushes during this continuous rotation of the rotor causes the wear on the rings and fiber brushes and generates heat, and even noise in the system, especially in the case of high RPM applications. The speed limit on the slip ring market, is about 10,000 RPM without cooling, or lubricating. The highest speed of slip rings on the market could be up to 20,000 RPM under a cooling, or lubricating system.
In some special applications, such as in high speed permanent magnet generators, in turbine engines, a slip ring may be required to operate at speeds up to 60,000 RPM.
The objective in the current invention is to provide a slip ring assembly for high speed applications, which require slip rings to operate at speeds more than 60,000 RPM.
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A detailed explanation of the preferred embodiment in the present invention with reference to
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The basic idea is that by using gears, we can always can make sure the relative speed between the rotor and the stator in each stage is <=10000 rpm. For example, if the speed of the rotor is 30,000 rpm, by designing the gears (see
If the gear ratio for Stage 1 is represented by the symbol λ1, for Stage 2 is λ2, . . . , the speed for the first rotor is represented by R1, for the second rotor R2 . . . , for the last rotor is Rn, the speed for first stator is represented by S1, for the second stator S2, . . . , for the last stator Sn=0, then, the speed relations can be represented by the following equations:
S1=Rλ1,
S2=R2/λ2, . . .
R2=S1, R3=S2, . . .
Rn=S(n−1).
The relative speed between rotor and stator for each stage is as follows:
R1−S1=R1(1−1/λ1),
Rn−Sn=Rn(1−1/λn).
For example: if R1=30,000 RPM, and λ1=1.5, then S1=20,000 RPM, so the relative speed between R1 and S1 is 10,000 RPM, which is considered good for a regular slip ring. Similarly, R2=S1=20,000 RPM, if λ2=2, then S2=R3=10,000 RPM. So for a 3-stage slip ring system, the relative speed between rotor and stator is always 10,000 RPM for each stage, which is good for a regular slip ring.
For another example: if R1=60,000 RPM , we will need a 6-stage slip ring system. By designing λ1=1.2, then S1=50,000 RPM, so the relative speed between R1 and S1 is 10,000 RPM. Similarly, R2=S1=50,000 RPM, by designing λ2=1.25, then S2=R3=40,000 RPM, . . . , and the last stator will be stationary.
Conclusion: for any high speed slip ring system, by selecting stage number n and designing gear ratios for each stage, we can always can make sure the relative speed between the rotor and the stator is <=10000 RPM for each stage, which is good for a regular slip ring.
