Calculation And Analysis Of Permanent Magnetic Coupling Losses

Permanent magnetic coupling are composed of two parts: a disc with containing a number of embedded magnets of alternating polarity. These are magnetized in the axial direction. The opposing shaft is connected to a pair of steel discs that have a simple copper sheet attached to the inner surfaces. The principle of operation itself is relatively straightforward: if the magnet disc has a velocity relative to the copper sheets , a current pattern will be produced in the copper discs. This current distribution will result in a circumferential force such that the copper sheet will endeavor to catch up with magnets. The normal operating torque will result in a small slip speed between the two halves of the coupling. An axial force is also present between the copper and magnets discs during normal operation which is a function of the slip speed of the coupling. The magnetic coupling offers some benefits of requiring no electrical contact , being reasonably tolerant of misalignment and serving to protect the motor when excessive loads or jammed load occur.The analysis of permanent magnetic coupling can utilize finite element method. This method is precise but also time consuming. Otherwise, there is another way to do it. This is a simple linear analysis based on a layer theory approach. This method was used extensively in sixties and seventies for the analysis of linear induction motors. It accommodates the eddy current patens in the copper sheets in a relatively straightforward fashion and is ideally suited to this type of coupling because each layer is homogeneous. The normal equivalent-circuit based approach would be difficult and inaccurate for this type of device. The model of permanent magnetic coupling is based on this layer theory approach which historically was developed to examine the behavior of linear machines. These type of machines commonly incorporate a sheet copper secondary similar to that used in the eddy current coupling. The model assumes that each permanent-magnet disc in the coupling is faced by a copper/steel sheet on either side. Any further magnet discs are then considered to be identical and therefore all force components should simply be multiplied by the number of additional magnet discs.This article consists of six parts shown as followed:(1) IntroductionThis part introduces permanent magnetic coupling briefly, the development situation, the development trend, and research contents of this article.(2) Summary of permanent magnetic couplingThis part introduces the structure, working principle and merits of permanent magnetic coupling. Classify magnetic coupling, compare with hydraulic coupling, variable frequency drive. Then introduces different types of permanent magnetic coupling.(3) Eddy current and lossUtilizing layer theory to simplify permanent magnetic coupling, establish the linear rise layer model of permanent magnetic coupling. Calculate eddy current, flux density and loss. Utilizing finite element method software ANSYS to analysis permanent magnetic coupling.(4) Temperature analysisUtilizing finite element method to analysis temperature distribution, calculate efficiency of heat conduction, heat convection.(5) Torque and axial forceUtilizing linear rise layer model of permanent magnetic coupling to calculate torque, axial force and working efficiency.(6) Conclusion and prospects In this part conclusion of this article and prospects of the study in the future are given.