Application Note

MAGNETIC GEAR: 2D FEM SIMULATION WITH EMWORKS2D INSIDE SOLIDWORKS

Finite element method (FEM) has demonstrated high reliability in the design and analysis of engineering systems [1]. It can be used to simulate any complicated geometry and for both linear and nonlinear problems. Moreover, Finite element analysis (FEA) can be used to solve both 3D and 2D approximated geometry. Additional advantages are gained when using 2D FEA such as saving time, running more iterations, etc. EMWorks2D, which is a 2D FEM plug-in inside SOLIDWORKs, provides an accurate solution to magnetic and electric problems in cases where the real-life problem can be approximated as a 2D problem.

In this article, EMWorks2D is used to compute magnetic results (magnetic flux density, field intensity, torque, etc.) of two coaxial magnetic gear models. The torque generated by both configurations will be predicted and investigated. Both results will be compared to the reference results.

The simulated models are shown in Figure 1. Model 1 has a smaller number of poles than model 2. In both cases, the inner rotor rotates with higher speed and develops lower torque.

(a)

(b)

Figure 1 - Simulated magnetic gear, a) model 1, b) model 2

Figure 2 contains contour lines plot of the magnetic vector potential generated inside the first model while Figure 2 illustrates the torque created in the inner rotor versus rotor angle of the same model (outer rotor and ferromagnetic pieces are fixed).

The following figures give the torque results of inner and outer rotor of both models (inner and outer rotors are rotating in opposite direction). For model 1, The average torque results are 67 N.m and 101 N.m respectively of the inner rotor and outer rotor (Figure 4). It can be concluded that the gear ratio is 1.5. It can be computed also using the pole-pairs number of the inner and outer rotors.

Figure 4 - Torque results model 1, a) inner rotor, b) outer rotor

The torque results of model 2 are shown in Figure 5. The HS rotor develops a torque of 41 N.m while the generated torque in LS rotor is about 175 N.m. Thus, both torques verify a gear ratio of 4.26 and are characterized by lower ripples. As can be seen from Figure 5b), the ripples are practically eliminated.

Figure 5 - Torque results model 2, a) inner rotor b) outer rotor