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Volume 52,Issue 4,2025 Table of Contents
1 Research on Multi-Physical Field Characteristics of Metallurgical Harmonic Intrusion in Transformers
2025, 52(4):341-355.
DOI: 10.12177/emca.2025.013
Abstract:
[Objective] To address the issue of component vibration and abnormal noise in transformers caused by harmonic intrusion during metallurgical production, this study investigates the evolution of metallurgical harmonic disturbances in multi-physical fields using a multi-physics coupling approach, combining simulation and experimental methods. [Methods] First, a coupling electromagnetic-mechanical-acoustic model of the transformer was proposed, taking harmonic disturbances into account. Electromagnetic force and vibration acceleration were selected as the characteristic parameters linking electromagnetic-mechanical and mechanical-acoustic fields, respectively. Based on electromagnetic coupling, the winding current, magnetic flux density, and electromagnetic force of the transformer were solved. The electromagnetic force was then used as the excitation for the mechanical model to calculate the vibration acceleration of the transformer core and windings. Subsequently, the vibration acceleration was used as excitation for the acoustic model to calculate the sound pressure and the variations in sound pressure level, thereby realizing the multi-field coupling process across electromagnetic, mechanical, and acoustic domains. The spatiotemporal distributions and variations of each field under various disturbance modes were simulated. The evolution of disturbances in the multi-physical fields was analyzed using the characteristic parameters. The effects of harmonic and interharmonic components' disturbances on the transformer's multi-field parameters were studied through simulation. Additionally, a test platform for dynamic simulation was built to collect vibration and noise signals from the transformer under different disturbance modes. [Results] The results showed that when metallurgical harmonics intruded into the transformer, the multi-field information of the components increased with higher load rate and harmonic frequency. Interharmonic components caused more significant disturbances to the transformer than harmonic components in adjacent frequency domain. The accuracy of the proposed model was verified through simulation-experiment comparisons. [Conclusion] Based on simulation and experimental results, the most significant interharmonic component 97 Hz in metallurgical harmonics is selected as a typical characterization parameter. A mapping relationship between different levels of the 97 Hz interharmonic and the vibration of transformer components is established, and an instability criterion is developed. When the 97 Hz interharmonic content reaches 15%, it causes severe instability in the internal electromagnetic and mechanical environments within the transformer. The identification method provides support for situational awareness and equipment protection for transformers under metallurgical harmonic intrusion.
[Objective] To address the issue of component vibration and abnormal noise in transformers caused by harmonic intrusion during metallurgical production, this study investigates the evolution of metallurgical harmonic disturbances in multi-physical fields using a multi-physics coupling approach, combining simulation and experimental methods. [Methods] First, a coupling electromagnetic-mechanical-acoustic model of the transformer was proposed, taking harmonic disturbances into account. Electromagnetic force and vibration acceleration were selected as the characteristic parameters linking electromagnetic-mechanical and mechanical-acoustic fields, respectively. Based on electromagnetic coupling, the winding current, magnetic flux density, and electromagnetic force of the transformer were solved. The electromagnetic force was then used as the excitation for the mechanical model to calculate the vibration acceleration of the transformer core and windings. Subsequently, the vibration acceleration was used as excitation for the acoustic model to calculate the sound pressure and the variations in sound pressure level, thereby realizing the multi-field coupling process across electromagnetic, mechanical, and acoustic domains. The spatiotemporal distributions and variations of each field under various disturbance modes were simulated. The evolution of disturbances in the multi-physical fields was analyzed using the characteristic parameters. The effects of harmonic and interharmonic components' disturbances on the transformer's multi-field parameters were studied through simulation. Additionally, a test platform for dynamic simulation was built to collect vibration and noise signals from the transformer under different disturbance modes. [Results] The results showed that when metallurgical harmonics intruded into the transformer, the multi-field information of the components increased with higher load rate and harmonic frequency. Interharmonic components caused more significant disturbances to the transformer than harmonic components in adjacent frequency domain. The accuracy of the proposed model was verified through simulation-experiment comparisons. [Conclusion] Based on simulation and experimental results, the most significant interharmonic component 97 Hz in metallurgical harmonics is selected as a typical characterization parameter. A mapping relationship between different levels of the 97 Hz interharmonic and the vibration of transformer components is established, and an instability criterion is developed. When the 97 Hz interharmonic content reaches 15%, it causes severe instability in the internal electromagnetic and mechanical environments within the transformer. The identification method provides support for situational awareness and equipment protection for transformers under metallurgical harmonic intrusion.
2025, 52(4):356-366.
DOI: 10.12177/emca.2025.011
Abstract:
[Objective] To overcome the technical limitations of traditional position sensorless control for interior permanent magnet synchronous motor (IPMSM) across the full-speed range, this study aims to develop a position sensorless control strategy capable of achieving stable control across the full-speed range. Specifically, it seeks to address technical challenges such as insufficient observation accuracy of speed and angle at low speeds, significant system chattering at medium and high speeds, and poor stability during speed transitions, thereby achieving smooth position sensorless control switching from low to high speeds. [Methods] This study proposed a full-speed-range position sensorless control strategy based on a multimodal observer. At low speeds, an improved high-frequency square-wave injection method was adopted. By considering cross-coupling effects, a precise mathematical model of the motor was established to effectively extract rotor position information. At medium and high speeds, a novel sliding mode observer was designed, which significantly reduced system chattering by optimizing the switching function and introducing a boundary layer method. To ensure a smooth switching from low to high speeds, a fuzzy logic-based weighted switching algorithm was innovatively proposed, which ensured continuity and stability during switching by dynamically adjusting weight coefficients in real time. [Results] In the low-speed range (0~5% rated speed), the improved high-frequency square-wave injection method limited the position observation error within ±0.05 rad, demonstrating that incorporating cross-coupling effects improved the accuracy of rotor speed and angle estimation. In the medium- and high-speed range (5%~100% rated speed), the novel sliding mode observer effectively achieved position sensorless control and reduced system chattering amplitude by about 60%. After applying the weighted switching algorithm, torque fluctuations during speed switching decreased by 45%, and speed overshoot was maintained within 2%. Compared to traditional methods, the proposed strategy improved control accuracy by over 30% and enhanced dynamic response speed by 25% across the full-speed range. [Conclusion] The proposed full-speed-range position sensorless control strategy effectively addresses the control challenges of IPMSM across the full-speed range. The improved high-frequency square-wave injection method significantly enhances observation accuracy at low speeds, while the novel sliding mode observer efficiently suppresses system chattering at medium and high speeds, and the fuzzy logic-based weighted switching algorithm achieves smooth transitions between speed ranges. Simulation and experimental results fully validate the feasibility and superiority of the proposed strategy, offering a new solution for practical sensorless applications in IPMSM.
[Objective] To overcome the technical limitations of traditional position sensorless control for interior permanent magnet synchronous motor (IPMSM) across the full-speed range, this study aims to develop a position sensorless control strategy capable of achieving stable control across the full-speed range. Specifically, it seeks to address technical challenges such as insufficient observation accuracy of speed and angle at low speeds, significant system chattering at medium and high speeds, and poor stability during speed transitions, thereby achieving smooth position sensorless control switching from low to high speeds. [Methods] This study proposed a full-speed-range position sensorless control strategy based on a multimodal observer. At low speeds, an improved high-frequency square-wave injection method was adopted. By considering cross-coupling effects, a precise mathematical model of the motor was established to effectively extract rotor position information. At medium and high speeds, a novel sliding mode observer was designed, which significantly reduced system chattering by optimizing the switching function and introducing a boundary layer method. To ensure a smooth switching from low to high speeds, a fuzzy logic-based weighted switching algorithm was innovatively proposed, which ensured continuity and stability during switching by dynamically adjusting weight coefficients in real time. [Results] In the low-speed range (0~5% rated speed), the improved high-frequency square-wave injection method limited the position observation error within ±0.05 rad, demonstrating that incorporating cross-coupling effects improved the accuracy of rotor speed and angle estimation. In the medium- and high-speed range (5%~100% rated speed), the novel sliding mode observer effectively achieved position sensorless control and reduced system chattering amplitude by about 60%. After applying the weighted switching algorithm, torque fluctuations during speed switching decreased by 45%, and speed overshoot was maintained within 2%. Compared to traditional methods, the proposed strategy improved control accuracy by over 30% and enhanced dynamic response speed by 25% across the full-speed range. [Conclusion] The proposed full-speed-range position sensorless control strategy effectively addresses the control challenges of IPMSM across the full-speed range. The improved high-frequency square-wave injection method significantly enhances observation accuracy at low speeds, while the novel sliding mode observer efficiently suppresses system chattering at medium and high speeds, and the fuzzy logic-based weighted switching algorithm achieves smooth transitions between speed ranges. Simulation and experimental results fully validate the feasibility and superiority of the proposed strategy, offering a new solution for practical sensorless applications in IPMSM.
2025, 52(4):367-375.
DOI: 10.12177/emca.2025.017
Abstract:
[Objective] Silicon carbide (SiC) devices, characterized by low switching losses and high voltage endurance, demonstrate significant advantages in modular multilevel converter (MMC) for medium-voltage applications. However, submodules based on SiC devices generate high du/dt and di/dt during switching transients, leading to severe electromagnetic interference that compromises system safety. [Methods] To address this issue, this study analyzed the stray capacitance distribution characteristics of submodules based on the MMC topology. By performing an equivalent transformation of stray capacitance, an equivalent circuit model for common-mode interference was established. On this basis, a novel common-mode current suppression strategy was proposed, employing carrier phase-shifted pulse width modulation with complementary submodules triggering pulses in the upper and lower bridge arms. By adjusting the carrier phase of the complementary submodules, common-mode current suppression was achieved. [Results] Simulation results showed that the proposed method effectively maintained submodules capacitor voltage balance and ensured high-quality AC-side output waveforms, both of which were critical performance factors for MMC. Compared to conventional methods, the proposed strategy reduced the peak common-mode current by 43%, demonstrating better suppression capability and validating its effectiveness. [Conclusion] The proposed method effectively suppresses common-mode interference current, enhancing the overall integrity and reliability of SiC MMC. These findings provide valuable insights into the advancement of power electronics technology in medium-voltage applications.
[Objective] Silicon carbide (SiC) devices, characterized by low switching losses and high voltage endurance, demonstrate significant advantages in modular multilevel converter (MMC) for medium-voltage applications. However, submodules based on SiC devices generate high du/dt and di/dt during switching transients, leading to severe electromagnetic interference that compromises system safety. [Methods] To address this issue, this study analyzed the stray capacitance distribution characteristics of submodules based on the MMC topology. By performing an equivalent transformation of stray capacitance, an equivalent circuit model for common-mode interference was established. On this basis, a novel common-mode current suppression strategy was proposed, employing carrier phase-shifted pulse width modulation with complementary submodules triggering pulses in the upper and lower bridge arms. By adjusting the carrier phase of the complementary submodules, common-mode current suppression was achieved. [Results] Simulation results showed that the proposed method effectively maintained submodules capacitor voltage balance and ensured high-quality AC-side output waveforms, both of which were critical performance factors for MMC. Compared to conventional methods, the proposed strategy reduced the peak common-mode current by 43%, demonstrating better suppression capability and validating its effectiveness. [Conclusion] The proposed method effectively suppresses common-mode interference current, enhancing the overall integrity and reliability of SiC MMC. These findings provide valuable insights into the advancement of power electronics technology in medium-voltage applications.
2025, 52(4):376-388.
DOI: 10.12177/emca.2025.015
Abstract:
[Objective] Currently, isolating switches have been widely used in power grids, but research on their fault diagnosis remains limited compared to equipment such as transformers and circuit breakers. The accurate identification of fault types in isolating switches through vibration signals during their operation is crucial for the normal operation of power grids and the safety of maintenance personnel. [Methods] This paper proposes an improved frilled lizard optimization (FLO) algorithm by incorporating an adaptive t-distribution perturbation strategy (tFLO). Subsequently, the algorithm is applied to parameter optimization for both sequential variational mode decomposition (SVMD) and least squares support vector machine (LSSVM) to achieve accurate fault identification in isolating switches. Firstly, an adaptive t-distribution perturbation strategy was incorporated to improve the FLO algorithm. The tFLO-SVMD then decomposed experimental data to obtain optimal modal components. Next, the refined composite multiscale fuzzy dispersion entropy (RCMFDE) of the modal components was calculated to obtain a high-dimensional feature matrix. Finally, the tFLO-LSSVM algorithm was used to classify faults in multiple sets of low dimensional feature matrices obtained by reducing the dimensionality of the high-dimensional matrices through kernel principal component analysis (KPCA). [Results] The fault diagnosis method based on tFLO-SVMD-LSSVM-RCMFDE proposed in this study for a 220 kV high voltage isolating switch achieved an accuracy of 97.92%, demonstrating effective identification of various fault types in isolating switches. [Conclusion] There are problems of slow computation speed and poor robustness of modal centers in the intrinsic mode function (IMF) components decomposed by traditional VMD methods, necessitating additional optimization of the number of modes k. The SVMD algorithm can effectively address these issues while achieving more detailed decomposition. Additionally, entropy calculation can effectively quantify the complexity and uncertainty of time series, and fuzzy dispersion entropy (FDE) has the advantages of short computation time and strong anti-interference. Compared to FDE, RCMFDE demonstrates better stability and more comprehensive feature representation. The combination of tFLO-SVMD and RCMFDE can effectively distinguish vibration signals of different fault types. In summary, this study proves that the classification method based on tFLO-SVMD-LSSVM-RCMFDE can effectively identify faults in isolating switches with high accuracy.
[Objective] Currently, isolating switches have been widely used in power grids, but research on their fault diagnosis remains limited compared to equipment such as transformers and circuit breakers. The accurate identification of fault types in isolating switches through vibration signals during their operation is crucial for the normal operation of power grids and the safety of maintenance personnel. [Methods] This paper proposes an improved frilled lizard optimization (FLO) algorithm by incorporating an adaptive t-distribution perturbation strategy (tFLO). Subsequently, the algorithm is applied to parameter optimization for both sequential variational mode decomposition (SVMD) and least squares support vector machine (LSSVM) to achieve accurate fault identification in isolating switches. Firstly, an adaptive t-distribution perturbation strategy was incorporated to improve the FLO algorithm. The tFLO-SVMD then decomposed experimental data to obtain optimal modal components. Next, the refined composite multiscale fuzzy dispersion entropy (RCMFDE) of the modal components was calculated to obtain a high-dimensional feature matrix. Finally, the tFLO-LSSVM algorithm was used to classify faults in multiple sets of low dimensional feature matrices obtained by reducing the dimensionality of the high-dimensional matrices through kernel principal component analysis (KPCA). [Results] The fault diagnosis method based on tFLO-SVMD-LSSVM-RCMFDE proposed in this study for a 220 kV high voltage isolating switch achieved an accuracy of 97.92%, demonstrating effective identification of various fault types in isolating switches. [Conclusion] There are problems of slow computation speed and poor robustness of modal centers in the intrinsic mode function (IMF) components decomposed by traditional VMD methods, necessitating additional optimization of the number of modes k. The SVMD algorithm can effectively address these issues while achieving more detailed decomposition. Additionally, entropy calculation can effectively quantify the complexity and uncertainty of time series, and fuzzy dispersion entropy (FDE) has the advantages of short computation time and strong anti-interference. Compared to FDE, RCMFDE demonstrates better stability and more comprehensive feature representation. The combination of tFLO-SVMD and RCMFDE can effectively distinguish vibration signals of different fault types. In summary, this study proves that the classification method based on tFLO-SVMD-LSSVM-RCMFDE can effectively identify faults in isolating switches with high accuracy.
2025, 52(4):389-401.
DOI: 10.12177/emca.2025.0019
Abstract:
[Objective] To address the issue of electromagnetic vibration and noise in spoke-type permanent magnet synchronous motor (STPMSM), this study investigates the impact of additional air gap between the stator teeth and yoke on the acoustic performance of STPMSM. The aim is to reduce electromagnetic vibration and noise by designing an optimal additional air-gap structure. [Methods] Firstly, a finite element model of the STPMSM was developed to analyze its electromagnetic field characteristics. The electromagnetic force was decomposed into radial and tangential components using the Maxwell stress tensor method and two-dimensional Fourier transform to examine its spatiotemporal distribution. Then, a 10-pole 12-slot STPMSM test platform was constructed to simulate vibration and noise responses under actual operating conditions. Modal analysis, hammer response experiments, and frequency response function measurements were conducted to validate the simulation results. Finally, a comparative study was performed between uniform and non-uniform additional air gap structures, evaluating the effects of triangular and convex tooth-yoke separation structures on overall acoustic performance. [Results] Both simulation and experimental results demonstrated that introducing an additional air gap between the stator teeth and yoke reduced the motor's sound pressure level by approximately 2.3 dB. Finite element analysis revealed that the dominant radial force components corresponded to specific spatial harmonics, aligning with actual noise frequencies. Although the non-uniform additional air gap introduced new spatiotemporal components of electromagnetic force, its impact on overall acoustic performance was negligible. Furthermore, the stator with a triangular tooth-yoke separation structure exhibited significantly better noise reduction performance than the convex structure. [Conclusion] This study confirms that the additional air gap effectively reduces electromagnetic vibration and noise in STPMSM. The difference in acoustic performance between uniform and non-uniform air gaps was not significant, while the triangular tooth-yoke separation structure demonstrated superior noise reduction capabilities. Furthermore, optimizing additional air gap parameters using genetic algorithms can further enhance acoustic performance, offering new insights and methodologies for motor noise control.
[Objective] To address the issue of electromagnetic vibration and noise in spoke-type permanent magnet synchronous motor (STPMSM), this study investigates the impact of additional air gap between the stator teeth and yoke on the acoustic performance of STPMSM. The aim is to reduce electromagnetic vibration and noise by designing an optimal additional air-gap structure. [Methods] Firstly, a finite element model of the STPMSM was developed to analyze its electromagnetic field characteristics. The electromagnetic force was decomposed into radial and tangential components using the Maxwell stress tensor method and two-dimensional Fourier transform to examine its spatiotemporal distribution. Then, a 10-pole 12-slot STPMSM test platform was constructed to simulate vibration and noise responses under actual operating conditions. Modal analysis, hammer response experiments, and frequency response function measurements were conducted to validate the simulation results. Finally, a comparative study was performed between uniform and non-uniform additional air gap structures, evaluating the effects of triangular and convex tooth-yoke separation structures on overall acoustic performance. [Results] Both simulation and experimental results demonstrated that introducing an additional air gap between the stator teeth and yoke reduced the motor's sound pressure level by approximately 2.3 dB. Finite element analysis revealed that the dominant radial force components corresponded to specific spatial harmonics, aligning with actual noise frequencies. Although the non-uniform additional air gap introduced new spatiotemporal components of electromagnetic force, its impact on overall acoustic performance was negligible. Furthermore, the stator with a triangular tooth-yoke separation structure exhibited significantly better noise reduction performance than the convex structure. [Conclusion] This study confirms that the additional air gap effectively reduces electromagnetic vibration and noise in STPMSM. The difference in acoustic performance between uniform and non-uniform air gaps was not significant, while the triangular tooth-yoke separation structure demonstrated superior noise reduction capabilities. Furthermore, optimizing additional air gap parameters using genetic algorithms can further enhance acoustic performance, offering new insights and methodologies for motor noise control.
2025, 52(4):402-411.
DOI: 10.12177/emca.2025.010
Abstract:
[Objective] The submersible permanent magnet synchronous motor (SPMSM) offers advantages such as high safety, reliability, efficiency, and fast response, making it an ideal replacement for low-efficiency asynchronous submersible motors. Its control performance directly affects the stability of submersible electric pumps and the efficiency of oil extraction. However, due to the harsh working conditions in oil wells, installing position sensors in submersible motors is impractical. To address this issue, this study establishes a mathematical model of the motor under high-frequency excitation and proposes a sensorless active disturbance rejection control (ADRC) strategy using the high-frequency square-wave injection method. [Methods] A filterless approach was employed to separate fundamental and high-frequency current signals, allowing the extraction of rotor position information from high-frequency current signals. To enhance the accuracy of speed estimation in the medium- and high-speed range, a Luenberger observer with error feedback correction was implemented to reduce observation errors in motor speed and rotor position. Additionally, analyzing the influence of uncertain disturbances on the system, on the basis of that, a speed regulator based on ADRC was designed and integrated into the vector control system. [Results] To verify the performance of the high-frequency square-wave injection method based on ADRC technology at low speeds, a system simulation model was developed using Matlab/Simulink. The simulation results indicated that the proposed system exhibited excellent speed-tracking performance and high rotor position estimation accuracy, with a fast dynamic response and high steady-state accuracy. Furthermore, the control algorithm effectively followed the actual speed under sudden load disturbances and restored stability within a short period, validating the effectiveness and feasibility of the proposed control strategy. [Conclusion] The proposed method successfully mitigates the impact of load disturbances across a wide speed regulation range.
[Objective] The submersible permanent magnet synchronous motor (SPMSM) offers advantages such as high safety, reliability, efficiency, and fast response, making it an ideal replacement for low-efficiency asynchronous submersible motors. Its control performance directly affects the stability of submersible electric pumps and the efficiency of oil extraction. However, due to the harsh working conditions in oil wells, installing position sensors in submersible motors is impractical. To address this issue, this study establishes a mathematical model of the motor under high-frequency excitation and proposes a sensorless active disturbance rejection control (ADRC) strategy using the high-frequency square-wave injection method. [Methods] A filterless approach was employed to separate fundamental and high-frequency current signals, allowing the extraction of rotor position information from high-frequency current signals. To enhance the accuracy of speed estimation in the medium- and high-speed range, a Luenberger observer with error feedback correction was implemented to reduce observation errors in motor speed and rotor position. Additionally, analyzing the influence of uncertain disturbances on the system, on the basis of that, a speed regulator based on ADRC was designed and integrated into the vector control system. [Results] To verify the performance of the high-frequency square-wave injection method based on ADRC technology at low speeds, a system simulation model was developed using Matlab/Simulink. The simulation results indicated that the proposed system exhibited excellent speed-tracking performance and high rotor position estimation accuracy, with a fast dynamic response and high steady-state accuracy. Furthermore, the control algorithm effectively followed the actual speed under sudden load disturbances and restored stability within a short period, validating the effectiveness and feasibility of the proposed control strategy. [Conclusion] The proposed method successfully mitigates the impact of load disturbances across a wide speed regulation range.
2025, 52(4):412-421.
DOI: 10.12177/emca.2025.022
Abstract:
[Objective] Canned permanent magnet synchronous motor (CPMSM) demonstrates excellent performance, including high efficiency and high power density. Due to its compact size, lightweight design, stable and reliable operation, and low maintenance requirements, it is widely used in precision-controlled industrial equipment such as vacuum pumps. During the vacuum pumping process, air may flow into the vacuum environment, causing the vacuum pump to operate under high load conditions and leading to CPMSM overload. [Methods] This study established a co-simulation model using Simulink and Ansys to analyze the electromagnetic and thermal fields of the motor, determining the safe operation duration and the variations in the electromagnetic field under overload conditions. Taking a 1.5 kW CPMSM as an example, different overload torque multiples were set to simulate impact loads. The one-way coupling method was used to calculate the temperature rise in the winding insulation and permanent magnets under overload conditions. [Results] The results showed that the winding insulation of the CPMSM reached its temperature limit after 516 s under 1.8 times the rated load. Continued operation beyond this limit would cause motor damage, while the permanent magnets could still function safely under this load. Therefore, the motor's safe operating time under overload was 516 s. In addition, the study revealed that after overload, regions with higher stator yoke magnetic flux density increased compared to rated load conditions, while the fundamental amplitude of the air gap flux density decreased, and the fundamental amplitude of the back electromotive force increased. After overload, motor's losses increased, while both efficiency and power factor decreased. Additionally, the torque fluctuations first decreased and then increased. [Conclusion] By establishing a simulation model, this paper provides an in-depth analysis of CPMSM's operating characteristics under overload conditions, providing a scientific basis for accurately determining the safe response time after temperature rise. The study summarizes the variations in electromagnetic performance after overloading, which is crucial for improving CPMSM performance.
[Objective] Canned permanent magnet synchronous motor (CPMSM) demonstrates excellent performance, including high efficiency and high power density. Due to its compact size, lightweight design, stable and reliable operation, and low maintenance requirements, it is widely used in precision-controlled industrial equipment such as vacuum pumps. During the vacuum pumping process, air may flow into the vacuum environment, causing the vacuum pump to operate under high load conditions and leading to CPMSM overload. [Methods] This study established a co-simulation model using Simulink and Ansys to analyze the electromagnetic and thermal fields of the motor, determining the safe operation duration and the variations in the electromagnetic field under overload conditions. Taking a 1.5 kW CPMSM as an example, different overload torque multiples were set to simulate impact loads. The one-way coupling method was used to calculate the temperature rise in the winding insulation and permanent magnets under overload conditions. [Results] The results showed that the winding insulation of the CPMSM reached its temperature limit after 516 s under 1.8 times the rated load. Continued operation beyond this limit would cause motor damage, while the permanent magnets could still function safely under this load. Therefore, the motor's safe operating time under overload was 516 s. In addition, the study revealed that after overload, regions with higher stator yoke magnetic flux density increased compared to rated load conditions, while the fundamental amplitude of the air gap flux density decreased, and the fundamental amplitude of the back electromotive force increased. After overload, motor's losses increased, while both efficiency and power factor decreased. Additionally, the torque fluctuations first decreased and then increased. [Conclusion] By establishing a simulation model, this paper provides an in-depth analysis of CPMSM's operating characteristics under overload conditions, providing a scientific basis for accurately determining the safe response time after temperature rise. The study summarizes the variations in electromagnetic performance after overloading, which is crucial for improving CPMSM performance.
2025, 52(4):422-431.
DOI: 10.12177/emca.2025.018
Abstract:
[Objective] Fractional-slot concentrated winding (FSCW) dual-rotor motor, due to its unique winding distribution, generates abundant magnetomotive force harmonics in the air gap. During direct starting, the motor generates a large amount of inrush current and torque pulsation. To address this issue, this paper analyzes the electromagnetic torque characteristics under two starting methods-hard starting and soft starting-to evaluate whether these methods are conducive to the stable operation of the motor. Additionally, the validity of the virtual displacement method under these two starting conditions is verified. [Methods] This paper first introduced the basic structure and working principle of the FSCW axial dual-rotor motor. A mathematical model of the motor was then established based on winding theory. Based on simulation results, the transient and steady-state processes of hard and soft starting were analyzed, as well as the torque characteristics at different stator-rotor axial angles under both starting conditions. Next, the electromagnetic torque expression was derived based on the virtual displacement method. Finally, the electromagnetic torque under both starting conditions was discussed by combining the virtual displacement method and simulation results. [Results] Simulation data showed that during hard starting, the electromagnetic torque increased sharply, and the subsequent torque waveforms exhibited significant fluctuations and noticeable oscillations. Over time, the torque fluctuations gradually stabilized and reached a steady state, with the transient peak about twice the steady-state peak. Under both hard and soft starting conditions, the simulated electromagnetic torque was slightly lower than the result calculated by the virtual displacement method. The peak values and fluctuations of the simulation waveform showed significant variations when the stator-rotor axial angle was altered. [Conclusion] The results indicate that hard starting is not conducive to the stable operation of the motor. The stator-rotor axis angle affects both the magnitude of the electromagnetic torque and the torque pulsation. The simulated electromagnetic torque aligns well with the theoretical value, and the derived expression shows high accuracy, serving as a reference for subsequent calculations of the motor's electromagnetic torque.
[Objective] Fractional-slot concentrated winding (FSCW) dual-rotor motor, due to its unique winding distribution, generates abundant magnetomotive force harmonics in the air gap. During direct starting, the motor generates a large amount of inrush current and torque pulsation. To address this issue, this paper analyzes the electromagnetic torque characteristics under two starting methods-hard starting and soft starting-to evaluate whether these methods are conducive to the stable operation of the motor. Additionally, the validity of the virtual displacement method under these two starting conditions is verified. [Methods] This paper first introduced the basic structure and working principle of the FSCW axial dual-rotor motor. A mathematical model of the motor was then established based on winding theory. Based on simulation results, the transient and steady-state processes of hard and soft starting were analyzed, as well as the torque characteristics at different stator-rotor axial angles under both starting conditions. Next, the electromagnetic torque expression was derived based on the virtual displacement method. Finally, the electromagnetic torque under both starting conditions was discussed by combining the virtual displacement method and simulation results. [Results] Simulation data showed that during hard starting, the electromagnetic torque increased sharply, and the subsequent torque waveforms exhibited significant fluctuations and noticeable oscillations. Over time, the torque fluctuations gradually stabilized and reached a steady state, with the transient peak about twice the steady-state peak. Under both hard and soft starting conditions, the simulated electromagnetic torque was slightly lower than the result calculated by the virtual displacement method. The peak values and fluctuations of the simulation waveform showed significant variations when the stator-rotor axial angle was altered. [Conclusion] The results indicate that hard starting is not conducive to the stable operation of the motor. The stator-rotor axis angle affects both the magnitude of the electromagnetic torque and the torque pulsation. The simulated electromagnetic torque aligns well with the theoretical value, and the derived expression shows high accuracy, serving as a reference for subsequent calculations of the motor's electromagnetic torque.
2025, 52(4):432-441.
DOI: 10.12177/emca.2025.021
Abstract:
[Objective] Reducing cogging torque is a key issue in motor design. It is widely recognized that slotting the stator teeth of permanent magnet synchronous motor (PMSM) can effectively suppress cogging torque. However, the feasibility of using this method for canned permanent magnet synchronous motor (CPMSM) remains unclear. [Methods] This study investigated a 6-pole, 9-slot CPMSM. A motor model was developed using the finite element method, and stator tooth slotting was implemented. Based on the derivation of the cogging torque expression for the CPMSM, the influence of auxiliary stator tooth slots on cogging torque was analyzed. In addition, the effects of slot number, slot shape, slot position, slot opening width, and slot depth on cogging torque reduction were studied, along with a performance comparison before and after slotting. [Results] The research results showed that, compared with conventional PMSM, the presence of a shielding sleeve in CPMSM reduced the effectiveness of auxiliary slotting for cogging torque suppression. Furthermore, identified as two rectangular slots with a width of w=2.6 mm, a depth of h=0.4 mm, and an offset angle of ??=12.8°, which achieved the best suppression performance on the CPMSM's cogging torque. [Conclusion] The proposed method of slotting the stator teeth of CPMSM to suppress cogging torque is feasible. Additionally, auxiliary slotting reduces the amplitude of air gap flux density and shielding sleeve losses, thereby improving motor efficiency. This study provides valuable insights for the optimization and design of CPMSM.
[Objective] Reducing cogging torque is a key issue in motor design. It is widely recognized that slotting the stator teeth of permanent magnet synchronous motor (PMSM) can effectively suppress cogging torque. However, the feasibility of using this method for canned permanent magnet synchronous motor (CPMSM) remains unclear. [Methods] This study investigated a 6-pole, 9-slot CPMSM. A motor model was developed using the finite element method, and stator tooth slotting was implemented. Based on the derivation of the cogging torque expression for the CPMSM, the influence of auxiliary stator tooth slots on cogging torque was analyzed. In addition, the effects of slot number, slot shape, slot position, slot opening width, and slot depth on cogging torque reduction were studied, along with a performance comparison before and after slotting. [Results] The research results showed that, compared with conventional PMSM, the presence of a shielding sleeve in CPMSM reduced the effectiveness of auxiliary slotting for cogging torque suppression. Furthermore, identified as two rectangular slots with a width of w=2.6 mm, a depth of h=0.4 mm, and an offset angle of ??=12.8°, which achieved the best suppression performance on the CPMSM's cogging torque. [Conclusion] The proposed method of slotting the stator teeth of CPMSM to suppress cogging torque is feasible. Additionally, auxiliary slotting reduces the amplitude of air gap flux density and shielding sleeve losses, thereby improving motor efficiency. This study provides valuable insights for the optimization and design of CPMSM.
2025, 52(4):442-452.
DOI: 10.12177/emca.2025.014
Abstract:
[Objective] This study aims to explore the efficiency and accuracy of distribution coefficient calculations for fractional-slot concentrated winding (FSCW) to further propose universally applicable calculation formulae. [Methods] Focusing on the distribution coefficients of FSCW, three innovative methods for calculating the distribution coefficient were proposed and comprehensively compared. The definition method, based on the classical theory of winding coefficients, derived the calculation formula through Fourier decomposition and the fundamental definition of the distribution coefficient. The harmonic synthesis method, utilizing the superposition principle of spatial magnetomotive force vectors, established a vector superposition model in a multi-pole-pair coordinate system. The phasor synthesis method incorporated the concept of time-domain phasors into spatial harmonic analysis to develop a winding distribution characterization method in the complex domain. Using theoretical analysis and numerical calculations as the basis, combined with analysis of case studies, the principles, applicability, and calculation characteristics of each method were summarized. [Results] Precise calculations for three typical slot-pole combinations were conducted. The results showed that the numerical values obtained from all three calculation methods were identical. [Conclusion] The definition method considers only the harmonic magnetomotive force amplitudes, but fails to effectively analyze the peak and valley distribution of the synthesized magnetomotive force along the axis. The harmonic synthesis method and phasor synthesis method incorporate both the amplitude and direction of the synthesized magnetomotive force phasors, thereby making them suitable for accurately determining the peak and valley distributions in the synthesized magnetomotive force harmonic. Derived from different perspectives, the three methods provide three distinct calculation formulae applicable to various distribution coefficient calculations, providing a theoretical basis for optimizing the design of FSCW.
[Objective] This study aims to explore the efficiency and accuracy of distribution coefficient calculations for fractional-slot concentrated winding (FSCW) to further propose universally applicable calculation formulae. [Methods] Focusing on the distribution coefficients of FSCW, three innovative methods for calculating the distribution coefficient were proposed and comprehensively compared. The definition method, based on the classical theory of winding coefficients, derived the calculation formula through Fourier decomposition and the fundamental definition of the distribution coefficient. The harmonic synthesis method, utilizing the superposition principle of spatial magnetomotive force vectors, established a vector superposition model in a multi-pole-pair coordinate system. The phasor synthesis method incorporated the concept of time-domain phasors into spatial harmonic analysis to develop a winding distribution characterization method in the complex domain. Using theoretical analysis and numerical calculations as the basis, combined with analysis of case studies, the principles, applicability, and calculation characteristics of each method were summarized. [Results] Precise calculations for three typical slot-pole combinations were conducted. The results showed that the numerical values obtained from all three calculation methods were identical. [Conclusion] The definition method considers only the harmonic magnetomotive force amplitudes, but fails to effectively analyze the peak and valley distribution of the synthesized magnetomotive force along the axis. The harmonic synthesis method and phasor synthesis method incorporate both the amplitude and direction of the synthesized magnetomotive force phasors, thereby making them suitable for accurately determining the peak and valley distributions in the synthesized magnetomotive force harmonic. Derived from different perspectives, the three methods provide three distinct calculation formulae applicable to various distribution coefficient calculations, providing a theoretical basis for optimizing the design of FSCW.
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沪ICP备16038578号-3
Electric Machines & Control Application ® 2025
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
沪ICP备16038578号-3
Electric Machines & Control Application ® 2025
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
