Presentation and analysis of a novel hybrid stepping motor with stator-permanent-magnet structure

Presentation and Performance Evaluation of a Novel Stator-Permanent-Magnet Hybrid Stepping Motor

“…Figure 7 shows the axial distribution of the PM torque density of the two motors based on Figure 6, in which Tpm0 represents the maximum PM torque of the unit stator core length (1 m) corresponding to the optimal PM flux density Bpm0, l1 and l2 represent the axial position where the PM flux density of the two motors are the same, and the shaded area represents the torque losses of the HSM compared to the SHSM. In terms of [2,18], the axial distribution of B pm along the stator core length in the HSM (with single PM and two rotor stacks) is non-uniform and would take the form of Figure 6, where h pm is the PM height in the magnetizing direction, taking into account the inter-lamination air-gaps. On the contrary, the axial distribution of B pm along the stator core length is uniform in the SHSM, which can be designed as B pm0 by using 2-D FEA or even the more accurate 3-D FEA.…”

“…It can be found that ∆ϕT reaches its maximum value ∆ϕTmax when Bpm = Bpm0, signifying the maximum PM torque according to Equations (9) and (10), and Bpm0 can thus be defined as the optimal PM flux density. In terms of [2,18], the axial distribution of Bpm along the stator core length in the HSM (with single PM and two rotor stacks) is non-uniform and would take the form of Figure 6, where hpm is the PM height in the magnetizing direction, taking into account the inter-lamination air-gaps. On the contrary, the axial distribution of Bpm along the stator core length is uniform in the SHSM, which can be designed as Bpm0 by using 2-D FEA or even the more accurate 3-D FEA.…”

“…The stator pole and yoke region under investigation and the positive direction of magnetic flux are shown in Figure 8a,b. Moreover, the simplified equivalent magnetic circuits corresponding to half of the HSM in Figure 8a and the whole SHSM in Figure 8b are built [18], as shown in Figure 9. Supposing that l e is the actual stator core length, according to the axial distribution characteristics of PM flux density and PM torque density shown in Figures 6 and 7, the PM torque comparison between the HSM and the SHSM is carried out in three cases:…”

“…The stator pole and yoke region under investigation and the positive direction of magnetic flux are shown in Figure 8a,b. Moreover, the simplified equivalent magnetic circuits corresponding to half of the HSM in Figure 8a and the whole SHSM in Figure 8b are built [18], as shown in Figure 9.…”

“…where k and j are positive integers which include the motor topologies in [18,19]. The proposed SHSM has the same operational principle as that of the HSM, due to structure equivalent transformation.…”