The miniaturization of the high-end equipment puts forward more stringent requirements on the torque density of permanent magnet (PM) servo motors. These motors usually work in high electromagnetic load conditions

resulting in a significant end flux leakage phenomenon

which makes its law of air-gap magnetic field modulation relatively large differences from the traditional PM motors. To further explore the law of air-gap field modulation

the end flux leakage distribution law of the PM motor under different electrical loads is researched

and an accurate two-dimensional (2-D) finite element (FE) equivalent model considering the end flux leakage is constructed. On this basis

based on the Maxwell stress tensor (MST) method

the contribution proportion of air-gap flux density modulation harmonics under different load conditions is deeply investigated. The influence law of the end flux leakage on the air-gap field modulation effects (FMEs) of the PM motor is revealed. In addition

the impact of key structural parameters on the harmonic contribution torque is analyzed. The results show that reasonable structure parameters can further increase the torque component of modulating harmonic contribution and enhance the torque density of the motor. Finally

a 22 kW prototype is manufactured

and the prototype test platform is built to verify the correctness and effectiveness of the theoretical analysis and the proposed method.