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The variable magnetic flux permanent magnet synchronous motor (VMF-PMSM) is one of the next-generation technologies to improve the efficiency of PMSM. The VMF-PMSM is expected to achieve high efficiency over a wide operating range by switching the magnetization states of the VMF-magnet, which has a low coercive field, through the application of the magnetic field from an armature coil. Achieving the desired torque in the VMF-PMSM requires to accurately grasp the relationship between the electrical control of the motor and the operating point of the magnet embedded in a rotating rotor, which is difficult to be measured. This presentation will show the approach for directly measuring the operating point of the VMF-magnet.
The VMF-PMSM with the system for real-time measurement of the magnetic field and the temperature of the rotor magnet was constructed (Fig. (a)). The rotor magnet consisted of a series lamination of the VMF-magnet [1] and the high coercive field magnets. The sensor probe with a Hall element and an NTC thermistor on a flexible printed circuit board was fixed on the surface of the rotor magnet and was electrically connected to a signal conditioner mounted on the rotor shaft, which includes a micro-controller and a Bluetooth module, enabling measurement and wireless communication. For driving the VMF-PMSM, a DSP (PE-Expert3) and an inverter unit (MWINV-2022A) manufactured by Myway Plus Corporation were used.
Figure (b) shows the current angle β dependence of torque during 3 Arms load rotation after magnetizing and demagnetizing the VFM-magnet with a d-axis current of ±60 A and an energizing time of 50 ms during a 600 rpm rotation at 26℃. The magnet torque in the magnetized state at β = 0° after a field weakening operation up to β = 90° decreased by 3.8% compared to before. This corresponded to a 4% decrease in the magnetic field of the rotor magnet, which was measured simultaneously during the same operation as mentioned above. In the presentation, the relationship between the electrical control of the motor and the operating point of the VMF-magnet will be considered using the measurement results of the torque and the magnet field.

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• Creative Commons BY Attribution 4.0 International
  

Keyword: REPM2025, motors

Date published:

Publisher: National Institute for Materials Science (NIMS)

Journal:

Conference: REPM2025 (2025-07-27 - 2025-07-31)

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Manuscript type: Not a journal article

MDR DOI: https://doi.org/10.48505/nims.5671

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Updated at: 2025-09-11 16:31:05 +0900

Published on MDR: 2025-09-11 16:20:06 +0900