Peixin Liang

Calculation of the Maximum Mechanical Stress on the Rotor of Interior Permanent-Magnet Synchronous Motors

This paper proposes a novel analytical method to calculate the maximum mechanical stress (MMS) on the rotor of the interior permanent-magnet synchronous motor with V-shaped rotor structure. Based on the traditional equivalent ring method, an improved method, which draws on the principle of equivalent centroid, is proposed to calculate the mechanical stress on the bilateral magnetic bridge. A rotor model with spokes is also built to calculate the mechanical stress on the central magnetic bridge. The stress concentration factor, together with its selection method, is also defined to calculate the MMS on the junctions. Then, the changing trends of the mechanical stress on the bilateral and central bridges are obtained along with the change in the V-shaped angle. The rotor faults of the two IPMSMs are analyzed based on the research results, and the optimized prototype is designed and fabricated. Experimental results of the optimized prototype show that the proposed equivalent methods have great applicability. Finally, the suggestion to design the V-shaped rotor structure is presented to determine the design rapidly and accurately.

Analytical Method for Iron Losses Reduction in Interior Permanent Magnet Synchronous Motor

Interior permanent magnet (PM) synchronous motors are widely used in electric vehicle, where limited space for motors is one of the most crucial challenges. This paper proposes an analytical design method to decrease iron losses, which saves much computation time compared with the parameter sweep method adopting finite-element analysis (FEA). The new method provides a design principle of the rotor, by which the harmonic magnetomotive force of the PM and the iron losses can be reduced significantly. This paper also takes the influence of the pole arc angle on iron loss reduction into consideration. The validity of the analytical technique is verified by 2-D FEA.

Magnet Shape Optimization of Surface-Mounted Permanent-Magnet Motors to Reduce Harmonic Iron Losses

Surface-mounted permanent-magnet (PM) synchronous motors are widely applied to electric vehicles, where iron losses reduction is a crucial target. This paper proposes a new method of PM shape optimization to reduce the harmonics of magnetic field and, hence, iron losses. The proposed method is based on the analytical calculation of magnetic field distribution with a non-uniform PM shape, which can save much computation time compared with the parameter sweep method. The validity of the method is verified by 2-D finite-element analysis.

Equivalent stator slot model of temperature field for high torque-density permanent magnet synchronous in-wheel motors accounting for winding type

Purpose – For high torque-density permanent magnet synchronous in-wheel motor, service life and electromagnetic performance are related directly to winding temperature. The purpose of this paper is to investigate the equivalent stator slot model to calculate the temperature of winding accurately. Design/methodology/approach – This paper analyzes the the law of heat flux transfer in slot, which points the main influence factors of equivalent stator slot model. Thermal network model is used to investigate the drawbacks of conventional equivalent model. Based on the law of heat transfer in stator slot, a new layered winding model is put forward. According to winding type and property of impregnations, detailed method and equivalent principle of the new model are presented. The accuracy of this new method has been verified experimentally. Findings – An accurate equivalent stator slot model should be built according to the low of heat transfer. According to theory analysis, the drawbacks of conventional equiva...

Analytical Prediction of Magnetic Field Distribution in Spoke-Type Permanent-Magnet Synchronous Machines Accounting for Bridge Saturation and Magnet Shape

This paper presents an analytical model for the prediction of magnetic field distribution in spoke-type permanent-magnet synchronous machines with rectangular magnets and magnetic bridges. The influence of saturation is considered. The magnetic bridges are equivalent to fan-shaped saturation regions. On the basis of the same pole-arc angle and identical magnetic energy, one rectangular magnet is simplified to two fan-shaped regions. The entire field domain is divided into eight types of simple subdomains, i.e., shaft, inner magnetic bridge, inner fan-shaped magnet, outer fan-shaped magnet, outer magnetic bridge, air gap, slot opening, and slot. The effect of magnetic field caused by armature reaction on the saturation of magnetic bridges is considered. The analytical expression of each subdomain is derived and the field solution is obtained by the boundary conditions. The analytical results at the no-load and on-load conditions are verified with the finite-element method.

An Improved Method for Armature-Reaction Magnetic Field Calculation of Interior Permanent Magnet Motors

This paper proposes an improved analytical method to calculate the armature-reaction magnetic field (ARMF) of interior permanent magnet motors. Based on the winding function, the armature-reaction magnetic motive force is divided into the q-axis component and the q-axis component to facilitate the analysis. Considering the flux paths, the difference of rotor magnetic potentials in the d-axis and the q-axis is illustrated, which improves the accuracy of the ARMF calculation. The validity of the analytical technique is verified by the 2-D finite-element analysis.

Equivalent stator slot model of temperature field for high torque-density permanent magnet synchronous in-wheel motor

This paper mainly investigates the equivalent stator slot model used in temperature field of high torque-density permanent magnet synchronous in-wheel motor. Analytical model of winding temperature shows that the conventional equivalent stator slot model has two drawbacks which increase the calculation error, especially for high torque-density motor. Based on the law of heat transfer in stator slot, a new layered winding model is put forward in this paper. The model is applicable to not only steady-state temperature field but also transient temperature field. The accuracy of this new method has been verified experimentally.

Analytical calculation of iron losses reduction for interior permanent magnet synchronous motor

Interior permanent magnet motors are widely applied to the industry, especially to the electric vehicle field that requires high power and high efficiency. For the limited space for the motors used in electric vehicle, it is difficult to cool them, which makes losses reduction to be a crucial target. As the main part of losses, iron loss is caused by the magnetomotive forces of permanent magnet and armature. With uniform air-gap, the flux density in the motors includes many harmonics, which increases iron losses. Some papers used pole eccentricity to optimize flux density waveforms and decrease the harmonics by finite element method (FEM). Actually, analytical calculation which points the influence factors for reduction of losses is more meaningful for designers. This paper presents a general analytical calculation to optimal rotor shape, which is effective to decrease iron losses. Considering the magnetomotive force of armature is different between distributed winding and concentrated winding, this paper also investigates the methods to decrease iron losses according to winding types.