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Magnet cracking is a common issue in external rotor motors. To investigate the causes of magnet cracking and propose solutions, the authors consider the effects of magnet shape, magnet and yoke material fit on the motor rotor magnets, perform a static analysis of the motor rotor. The simulation and test results show that the stress distribution of tile‐shaped magnets is better than that of rectangular magnets. The highest safety margin of 56.41% is achieved for the magnet and yoke material fit of DT4/N35(EH). The maximum force of the permanent magnet (PM) exceeds 22.38% of the stress limit when the material fit is DT4/SmCo28, which can lead to cracks in the PM. The results of this paper have important reference significance for the structural design of the external rotor motor and their safe and reliable operation. [ABSTRACT FROM AUTHOR]

Based on the ITO-HfO2-graphene stacked layers, a modulator that can achieve independent modulation of TE mode and TM mode within a single silicon waveguide is proposed. Graphene and ITO are employed as electrodes of graphene-HfO2-ITO capacitor. Under applied voltage, carriers accumulate within the 5 nm thick ITO film, leading to a modification of the optical dielectric constant. Using ITO's epsilon-near-zero behavior and its sensitivity to optical polarization, a modulation depth (MD) of no <2.5 dB/μm and an insertion loss of less than 0.054 dB/μm are achieved at the 1.55 μm. Furthermore, when modulating TE and TM modes independently, the mode crosstalk between the two modes is <0.02 dB/μm , demonstrating the high performance of the polarization-multiplexing (PM) modulator. At near-infrared band of 1.35 to 1.6 μm , the broadband properties of ITO and graphene are used to achieve an MD of no <2.2 dB/μm while maintaining mode crosstalk and insertion loss of less than 0.06 dB/μm. This modulator has robustness to top Si waveguide sidewall angle and compatibility with complementary metal oxide semiconductor processes. It is expected to be used in highly integrated polarization de-multiplexing and polarization switching systems. [ABSTRACT FROM AUTHOR]