Study On Linear Permanent Magnet Eddy Current Braking Method For Overwinding Protection Of The Hoisting Containers With Large Kinetic Energy Used In The Ultra-Deep Shaft

The Permanent Magnet Eddy Current Braking(PMECB)is a non-contact braking method with several advantages,such as no wear,no dust,no noise,no heat recession,energy saving and environmental protection.The principle of the PMECB is when there is relative movement between a conductor plate and permanent magnets,eddy currents are generated inside the conductor plate.Under the interaction of the magnetic field excited by the permanent magnets and the magnetic field excited by the eddy currents,the kinetic energy of the conductor plate is converted to the heat energy of the eddy currents.In the hoisting system used in the ultra-deep shaft,hoisting containers move rapidly in a straight reciprocating way in the shaft,and hoisting containers have a significant feature of large kinetic energy.The traditional friction-type overwinding protection systems fail to meet the safety requirements.The non-contact PMECB has a good application prospect in overwinding protection for the hoisting containers with large kinetic energy used in the ultra-deep shaft.However,at present,the research on PMECB mostly focuses on the braking of the rotating transmission shaft in vehicles,which fails to be directly used in the overwinding protection for the hoisting containers with linear motion.In this paper,the braking mechanism,key design parameters and structure optimization of the linear PMECB are systematically researched by theoretical model calculation,finite element simulation and experimental verification.On this basis,the linear PMECB overwinding protection device was designed,which can be applied to the overwinding protection of the hoisting containers with large kinetic energy used in the ultra-deep shaft.The main contents of this paper are as following:1)The analytical model and the finite element model of the linear PMECB were established,and the test system for the linear PMECB was built on the basis of the simulation model.2)The key design parameters of the linear PMECB were researched.Firstly,the influence mechanism of the key design parameters on the braking forceof the linear PMECB was analyzed.Then,the influence of the pole distance of the permanent magnets on the braking force was researched.The results show that there is an optimal pole distance of the permanent magnets,which can maximizes the braking force.Finally,according to the influence of the thickness of the conductor plate on the braking force,a fast and efficient method was proposed to determine the optimal thickness of the conductor plate.The method determines the optimal thickness of the conductor plate by providing an empirical formula,that is,when the thickness of the conductor plate is 0.6 times of the Standard Depth of Penetration(0.6*SDoP),the braking force can reach 90% of the maximum braking force.This method not only ensures a larger braking force,but also reduces the thickness of the conductor plate as much as possible.Furthermore,the total mass of the brake equipment was reduced.3)In order to solve the problems of low braking force and poor braking effect of the linear PMECB under a larger air gap length,the structure optimization of linear PMECB was carried out.Firstly,a new structure of the linear PMECB,H-type linear PMECB,was proposed.Then,through simulation and experimental research,it was found that the braking force of the H-type linear PMECB is about three times of that of the linear PMECB.Finally,the equivalent magnetic circuit method was used to model the H-type linear PMECB,and the mechanism of the H-type linear PMECB was revealed theoretically.4)According to the operation characteristics of the hoisting containers with large kinetic energy used in the ultra-deep shaft,linear PMECB overwinding protection method was proposed.Firstly,the force analysis of the hoisting containers was carried out.The design requirements and the design scheme of the linear PMECB overwinding protection device were proposed.Then,through the finite element simulation,the braking effect of the linear PMECB overwinding protection device was analyzed and evaluated.Finally,the thermal analysis of the linear PMECB overwinding protection device was carried out.Through the research of this paper,the key parameters of the linear PMECB were optimized.A fast and efficient method for determining the optimal thickness parameters of conductor plate was proposed.This method not only ensures a larger braking force,but also reduces the thickness of the conductor plate as much as possible.In order to solve the problem of insufficient braking force and poor retarding effect under a larger air gap length,the structure of the linear PMECB was optimized.After the structure optimization,the braking force can reach about three times of the original.The linear PMECB overwinding protection device was proposed,and this device can be applied to the overwinding protection of the hoisting containers with large kinetic energy used in the ultra-deep shaft.Under given conditions,the linear PMECB overwinding protection device can be used for braking the hoisting containers with an overwinding speed of 18.82 m/s.There are 94 figures,8 tables and 131 references.