Performance Analysis Of Permanent-Magnet Eddy-Current Couplings

Permanent-magnet eddy-current couplings have been widely used in pumps andfans which driven by medium and high power motors.The equipments have thefeatures of high efficiency and energy saving,low maintenance cost, simpleinstallation, high torque transmission, allow the impact load, the isolation vibrationand soft start. In the domestic,Studies about the device mainly adopts empiricalformula and amplification factor of safety design method which can not solve theproblem of power matching and energy waste effectively.This article researches andanalyses the magnetic field, eddy current density and magnetic transmission torque byadopting the method of combining theoretical analysis and finite element. Researchesmainly include the following aspects.(1) It is that establishing the mathematical model of air-gap magnetic inductionintensity of permanent-magnet eddy-current couplings and getting the expressions ofair-gap magnetic induction intensity by the equivalent magnetic charge method. Weget the distribution law of induction intensity and research the influence of change ofstructural parameters on magnetic flux intensity of air gap by MATLAB. Researcheshave shown that reducing the distance of air gap, increasing the thickness of themagnetic block, selecting reasonable number of magnetic poles can increasemagnetic.field strength of air gap.(2) Through solving maxwell’s equations,establishing the mathematical model forsolving eddy current density and getting the expression of eddy current density ofcopper plate. We analyse the law of distribution of eddy current density and researchthe influence of change of structural parameters on distribution of eddy currentdensity by MATLAB.Researches show that selecting rational pole logarithmic,increasing the thickness of the magnetic block, decreasing of air gap length canincrease eddy current density of copper plate.(3) Expression of transmission torque, input, output power and efficiency ofpermanent-magnet eddy-current couplings are deduced based on calculus and thetheory of electromagnetism. We analyse the distribution of magnetic transmission torque and research the influence of change of structural parameters on magnetictransmission torque by MATLAB.Researches show that there is a critical speed whichproduce the maximum of magnetic torque and output power. They also show thatselecting rational pole logarithmic, increasing the thickness of the magnetic block,reducing the air gap length,increasing the radius and electrical conductivity of driveplate can increase the magnetic transmission torque.(4) The magnetic field of air-gap, eddy current density and transmission torque ofthe permanent-magnet eddy-current couplings have been simulated by ANSYS. Theanalysis results of finite element are compared with the results which come from thefront analytic method.Researches show that although there is error between finiteelement results and analytic results, but the error is in the engineering allowable range.So it is can be used the analytic method in this paper to guide the design andmanufacture of permanent-magnet eddy-current couplings.