Study on the Overload Protection Characteristics of Rapid Disconnect Permanent Magnet Eddy Current Friction Torque Limiter

This article proposes a new type of high-power rapid disconnect permanent magnet (PM) eddy current friction torque limiter (RDPMEFTL) in response to the existing situation of the friction torque limiter's short life and poor reliability for overload protection devices for coal mine machinery. The RDPMEFTL's basic principle is to combine the permanent magnetic eddy current transmission mechanism with friction clutch and to use the permanent magnetic eddy current structure to control the friction torque limiter's opening and closing in order to achieve the transmission system's overload protection. First, the basic structure and working principle of the PM friction torque limiter are described, and then, a 2-D analytical model of the slotted PM drive structure is given based on the subdomain method, and the distributions of its air-gap magnetic field and conductor currents are investigated. Then, we obtain the characteristics of the changes of its electromagnetic axial force and torque with the slip and air gap. Second, the electromagnetic-mechanical coupling model of the whole drive system was established by combining the Karnopp friction model with the electromagnetic model, and the dynamics and electromagnetic response of the starting, overloading, and stopping processes were analyzed. Compared with the dry friction torque limiter, the RDPMEFTL will effectively improve the reliability and service life of the drive system, reduce the corresponding downtime maintenance work, and increase the productivity. Finally, tests were conducted with a small prototype and the test results were compared with the results of the analytical solution and 3-D finite element analysis, and they were basically consistent.