Analyzed working principle and starting process of asynchronous motor direct torque control system. In order to solve the problem of serious fluctuation of starting current in traditional control scheme, the author pu...Analyzed working principle and starting process of asynchronous motor direct torque control system. In order to solve the problem of serious fluctuation of starting current in traditional control scheme, the author puts forward a new kind of starting method which can limit voltage value to achieve the goal of reducing fluctuation of the current by increasing zero voltage vectors during the stage of starting. The author has also carried on simulation study on the system, and the result of simulation study shows that this method is effectual.展开更多
Wire race ball bearings have been widely used in high-tech weapons. The preload of a wire race ball bearing is crucial in engineering applications. In this study, a more effective approach is proposed for exact determ...Wire race ball bearings have been widely used in high-tech weapons. The preload of a wire race ball bearing is crucial in engineering applications. In this study, a more effective approach is proposed for exact determination of the wire race ball bearing preload. A new mathematical model of the preload and the starting torque of the wire race ball bearing was built using the theorem of the 3D rolling friction resistance and the non-conforming contact theory. Employing a wire race ball bearing with a 1000 mm diameter used in a specific type of aircraft simulating rotary table, the numerical analysis in MATLAB～ showed that the preload magnitude can be controlled in the range of 130–140 μm. As verification, the experimental results were in agreement with the theoretical results, and confirm the feasibility of this method. This new approach is more exact in the preload range of 10–158 μm than that computed by the numerical method reported in our previous work (Shan et al., 2007b). This implies that the present method contributes to more effectively preventing rolling noise, overturning moments and wear of the wire race ball bearing. The current research provides critical technical support for the engineering application of wire race ball bearings with large diameters.展开更多
文摘Analyzed working principle and starting process of asynchronous motor direct torque control system. In order to solve the problem of serious fluctuation of starting current in traditional control scheme, the author puts forward a new kind of starting method which can limit voltage value to achieve the goal of reducing fluctuation of the current by increasing zero voltage vectors during the stage of starting. The author has also carried on simulation study on the system, and the result of simulation study shows that this method is effectual.
基金Project supported by the National Natural Science Foundation of China (No. 50905039)the Natural Science Foundation of Hei-longjiang Province (No. E200924), China
文摘Wire race ball bearings have been widely used in high-tech weapons. The preload of a wire race ball bearing is crucial in engineering applications. In this study, a more effective approach is proposed for exact determination of the wire race ball bearing preload. A new mathematical model of the preload and the starting torque of the wire race ball bearing was built using the theorem of the 3D rolling friction resistance and the non-conforming contact theory. Employing a wire race ball bearing with a 1000 mm diameter used in a specific type of aircraft simulating rotary table, the numerical analysis in MATLAB～ showed that the preload magnitude can be controlled in the range of 130–140 μm. As verification, the experimental results were in agreement with the theoretical results, and confirm the feasibility of this method. This new approach is more exact in the preload range of 10–158 μm than that computed by the numerical method reported in our previous work (Shan et al., 2007b). This implies that the present method contributes to more effectively preventing rolling noise, overturning moments and wear of the wire race ball bearing. The current research provides critical technical support for the engineering application of wire race ball bearings with large diameters.
