Performance analysis of interior permanent magnet motors with sine-shaped permanent magnet
ZHEN Dongfang
SUN Dawei
LIU Mingkai
WANG Tong
MA Zenghua
SONG Hongzhi
LIU Yuan
Abstract：[Objective]Interior permanent magnet(IPM)motors are widely adopted as submersible motors in oil well applications due to their structural stability,high efficiency,and superior power factor.However,the constrained wellbore diameter and elevated ambient temperatures in deep-well environments impose stringent requirements for enhanced torque density and anti-demagnetization capability of IPM motors.To address these challenges,a novel sine-shaped permanent magnet(PM),synthesized from flat and arched PM,was adopted in this study.The adopted PM optimizes rotor space utilization above conventional flat PM,thereby increasing permanent magnet volume and d-axis permanent magnet thickness,improving torque density and anti-demagnetization capability of IPM motors.[Methods]Maintaining constant dimensions of the flat PM,the finite element analysis(FEA)was employed to systematically evaluate the effects of arched PM sagitta on short-circuit current,anti-demagnetization capability,and no-load and on-load electromagnetic performance.Moreover,the equivalent ring method was implemented to quantify the maximum stress of the rotor core under various sagittas,ensuring the mechanical integrity of the optimized rotor structure.[Results]Although the short-circuit current of the IPM motor will increase as the sagitta increases,its permanent magnets exhibit stronger anti-demagnetization capability.While increasing the sagitta will increase the maximum stress of the rotor core,it is much lower than the yield stress of the core material,meeting practical needs sufficiently.Moreover,the effect of a smaller sagitta on the reluctance torque of the IPM motor can be ignored.When the sagitta is greater than 3 mm,the maximum reluctance torque decreases significantly as the sagitta increases,while the total output torque keeps increasing and torque ripple decreases.[Conclusion]Taking into account the overall influence of the sagitta on the motor's performance,a suitable sine-shaped PM size was selected,and a prototype was manufactured and tested.The experimental results are in good agreement with the 2D FEA simulation results,verifying the accuracy of the simulation analysis,which provides a new approach for the rotor design of the IPM motors.
Keywords：interior permanent magnet motorsubmersible motorsine-shaped permanent magnetanti-demagnetization capabilitytorque densityshort-circuit currentstress of rotorequivalent ring method
Publication Date：2025-09-25
Online Publishing Date：2025-10-31(First online date of this platform, not the publication date of the document)
Pages：10( 584-593 )