Zehui Sun

Exploring the refined calculation theory of motor losses is not only the foundation for improving the wide‐range efficiency of motors but also the basis for the refined analysis of motor temperature rise and the design of cooling and heat dissipation structures, enabling the performance of motors to be fully utilized. This paper proposes a calculation method for analyzing the eddy current losses of AC winding based on the magnetic circuit method, and derives the expression of the AC winding impedance variation coefficient. It theoretically analyzes the mechanism of eddy current losses in AC winding and the intrinsic connection between losses and motor body and system parameters, providing a theoretical basis and technical support for the refined design of high‐density permanent magnet synchronous motors (PMSMs). The finite element simulation is used for verification, and the results show that the proposed calculation method for eddy current losses of AC winding is correct and effective.

Accurate measurement and separation of losses in electric drive motors is critical for iterative prototyping, enabling the development of high-precision cooling systems, loss-minimizing motor topologies, and energy-efficient control strategies. Although the total iron loss in permanent magnet synchronous motors (PMSMs) can be determined experimentally, the precise allocation of this loss between the stator and rotor has long been a challenge. To address this issue, this paper proposes a novel methodology with two key innovations. First, an experimental calibration strategy for the PMSM thermal model is developed that eliminates the dependence on prior knowledge of the precise loss distribution and allows independent model calibration. Second, based on this calibrated thermal model, we introduce an innovative temperature-based loss observer that improves the accuracy of the iron loss separation between the stator and rotor by using measured temperature data. Through these innovations, the proposed methodology, the proposed methodology simplifies the thermal modeling workflow, but also enables the generation of accurate iron loss profiles.

Signal injection method shows good performance in estimating the rotor position of permanent magnet synchronous motor (PMSM) at low speed, while the traditional uniaxial fixedphase signal injection (UFPSI) method will produce extra torque ripple and noise. This paper proposes a novel sensorless PMSM drive method based on biaxial random phase signal injection (BRPSI), which can simultaneously suppress both torque ripple and noise. To achieve this, an additional injected q -axis voltage, with its amplitude calculated in real time to satisfy different operating conditions, is used to counteract the torque ripple induced by the injected d -axis voltage. Meanwhile, the phase of the injected voltages is randomly switched to achieve a smooth current power spectral density (PSD) and attenuated noise level. The effectiveness of the proposed method is verified on a rapid control prototyping (RCP) platform, which demonstrates that the proposed method exhibits good speed and position tracking performance while simultaneously suppressing the torque ripples and noise caused by the injected signals.

This paper introduces simplified closed-form formulas for inductance calculations tailored for cases involving coaxial coils in extreme proximity. These formulas address the challenges associated with inductance calculations in the equivalent-circuit method (ECM) modeling of Thomson-coil actuators (TCAs), offering ultra-fast fault current-breaking capability for DC circuit breakers. The implementation of the ECM model using these closed-form formulas features high efficiency, accessibility, and transferability. Importantly, the present implementation of the multiphysics ECM model integrates comprehensive mechanical interactions, providing a benchmark approach for designing TCAs.

This article investigates the impact of Hall errors on the speed, rotor position, and current of joint motors in robots, focusing on brushless DC torque motors. On introducing the sensing principle of the Hall sensor in the torque motor system, the influence of circumferential installation errors and axial offset errors on the rotor position and current of the motor is derived analytically on the basis of the Hall vector signals. The results show that Hall errors generate rotor position errors characterized by the occurrence of specific harmonics with inherent deviations in rotor position, which in turn introduce the (2n-1)th current harmonics. The study proceeds to conduct simulations for a comparative evaluation of the degrees of influence exerted by circumferential installation errors and by axial offset errors on the motor speed, rotor position, and current. These findings are then validated through experiments, wherein the characteristics of Hall errors’ influence are elucidated via analysis of speed and current harmonics. This study provides a fresh methodology for analyzing errors in Hall sensors.

In the permanent-magnet synchronous machines (PMSMs), the temperature of the permanent magnets (PMs) is hard to estimate, because the heat transfer involving the rotor includes speed-dependent heat convection processes. This paper presents a Duhamel’s integral thermal model for estimating the PM temperature of a water-cooled PMSM. In the present model, the PM temperature transient under highly varying driving cycles is presented as the superposition of the responses to all the major unit-step excitations. The accurate response of the PM temperature to each unit-step excitation can be directly obtained by numerical simulations of the corresponding auxiliary problem with the aid of a high-fidelity CFD model of the PMSM. The present PM temperature estimation model features a universal functional formula, of which the parameterization procedure does not involve the solution nonuniqueness of an inverse identification method. Therefore, it can be easily parameterized for the common radial-flux water-cooled PMSMs.

Eccentricity in a permanent magnet synchronous motor (PMSM) can cause additional electromagnetic forces and resolver error, which in turn can lead to an aggravation of vibration and noise in the electric drive system. In this paper, the additional electromagnetic forces and the resulting vibration and noise under the conditions of the three-dimensional (3-D) static and dynamic motor eccentricities, the resolve error, and the coupling between these faults, are analytically derived and analyzed, with special emphasis on the coupling effect of the motor eccentricity and resolver error. The results of the present theoretical analyses agree well with those from the finite element simulations and the experimental measurements. It can be concluded from the results that the coupling between the 3-D motor eccentricity and the resolver error will induce additional electromagnetic forces with much more diverse spatial orders and frequencies.