Simulation of a Magnetic Coupling Machine

This article describes how to simulate a magnetic coupling machine using the electromechanical 3D finite element software embedded in SolidWorks. Magnetic couplings are generally used to transmit torque from one system to another where the magnetic transmission is required to maintain a hermetic seal to prevent leakage and contamination. 




The couplings are synchronous and the output shaft speed is exactly equal to the input speed and these types of coupling can be designed with a maximum 100% efficiency. Magnetic couplings are widely used in pump systems to isolate the electrical motor from the liquid. This has the advantage of removing the dynamic seals which have a finite lifetime and are prone to leakage, which can cause failure of the machine and contamination of the working fluid.




 A membrane/seal wall is located in the magnetic gap between the rotors providing complete isolation between the wet and dry systems. Magnetic couplings can also be used to introduce compliance into the drive train and can ultimately be used as a torque fuse to protect the system drive components. 




The motor considered here consists of permanent magnet arrays in the form of a steel rotor containing 12 permanent magnets and a steel stator with another 12 permanent magnet. The magnets are polarized in an alternating fashion radially inwards and outwards from the axis of the cylinder. The array setup provides linear and rotational coupling from the outer array (stator) to the inner array (rotor). The rotor is driven to turn by magnetic forces resulting from the permanent magnets. By creating multiple studies, the user can change the materials, current, number of turns, and the geometry of each part. EMS allows the user to keep the same assembly file and associate each study with a design table position.



All these features are very helpful for designers and can be used to determine the motor parameters responsible for optimizing the motor performances. In this example, four configurations were created to compute the torque applied on the rotor due to the magnetic fields.



 In this analysis, the inner set of magnets and the outer set are separated by an offset of between 0 and 15 degrees in steps of 5 degrees. The torque applied on the inner rotor increases as the angular offset increases.  The following plots are the results of a magnetostatic analysis of magnetic coupling machine. The first plot illustrates the magnetic flux density: 


Next plot shows the magnetic field intensity which is section clipped by advanced post processing tools of EMS:



This last plot s a vector plot which illustrates the magnetic force density:



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