Abstract
At present, because of their advantages of simple structure, low cost, low power consumption and high efficiency, single winding bearingless permanent magnet synchronous motors (SBPMSMs) have become one of the research hotspots in the bearingless technology field. However, a high motional-electromotive force (EMF) is generated by rotor rotation in the single winding, which already has side-effects on the normal suspension force current, and the suspension force response can be delayed. Because the method of double torque current inverse injection in the symmetrical winding allows the motional-EMFs of the corresponding phase windings to offset each other in the opposite direction, with no adverse effects on original performance, a T-shaped single winding configuration is proposed to realize precisely that effect. In this paper, the analytical expressions of the radial suspension force and torque are deduced and the motional-EMF and performance are analyzed by finite element method using the Ansys-Maxwell software. In addition, a suspension force vector closed loop control strategy is proposed to improve the suspension performance. The complete control strategy of torque and suspension force is designed based on the above motor winding configuration. Finite element analysis (FEA) is used to verify the T-shaped winding structure. The control strategy is demonstrated by software (MATLAB) simulation and an experimental prototype. These results show that the winding structure and the control strategy can achieve the desired effect, improving the radial suspension force.
Highlights
Bearingless permanent magnet synchronous motors (BPMSMs) have the advantages of high speed, high efficiency, high power density, no wear, no lubricant, no-pollution, maintenance-free, and so on.they have been widely investigated for centrifugal compressors, turbo molecular pumps, flywheel energy storage systems, etc. [1]
The magnitude of the suspension current required during normal operation is low, which results in insufficient utilization of the suspension winding which can provide sufficient suspension force under the maximum allowable eccentric displacement, further spread and application of BPMSMs has been hindered [3]
single winding bearingless permanent magnet synchronous motors (SBPMSMs) have been demonstrated in single-phase [6], three-phase [7], five-phase [8], and six-phase [9] stator winding types
Summary
Bearingless permanent magnet synchronous motors (BPMSMs) have the advantages of high speed, high efficiency, high power density, no wear, no lubricant, no-pollution, maintenance-free, and so on. Energies 2016, 9, 377 integrated into a single winding are increasingly being reported in international conference proceedings [4,5] This is mainly due to the stator model: the two needed magnetic fields are generated by feeding two groups of currents into the single set of windings, where the one can produce unbalanced forces for rotor suspension and another one generates the torque needed to control the rotation of the rotor. SBPMSMs have been demonstrated in single-phase [6], three-phase [7], five-phase [8], and six-phase [9] stator winding types These motors all have two different current sequences generating both levitation and rotation fluxes. The radial suspension force can be determined in real time and used for negative feedback by calculating the amplitude and phase of the two sets of currents, after the torque current and the suspension force current are observed directly in the static coordinate system
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