Analysis and Design of Novel High Speed Permanent Magnet Machine Considering Magnet Eddy Current Loss

Self Cite

High-speed rotating mechanical machinery is a developed, mature and reliable technology for many engineering applications. In high-speed permanent magnet machines, the rotor's permanent magnet PM is not strong enough to withstand the centrifugal force resulting from excessive rotational speed; thus, the PM material must be protected by a non-magnetic alloy sleeve. This paper presents a novel high-speed PM machine with solid rotor PM covered by a titanium retaining sleeve. The rotor stress condition is simplified as a plane stress problem according to the strength measurement of solid PM rotors in the high-speed PM motors. The analytical formulas for rotor stress are presented based on the polar coordinate displacement method. The proposed model is compared with a conventional model having auxiliary slots in stator teeth. Using a finite element analysis environment, the performance analysis shows that the proposed design has reduced magnet eddy current loss, cogging torque, and iron losses. The initial design is also optimized using a deterministic optimization algorithm that increases output torque by 26% compared to the initial design. INDEX TERMS Airgap flux density, finite element method, high-speed permanent magnet machine, magnet eddy current loss, retaining sleeve, rotor design, stress analysis.

“…The estimated eddy loss of PM is computed by the analytical equations presented in [19] given as follows:…”

Section: B Eddy Current Loss Pmmentioning

confidence: 99%

“…Specific designs were suggested in [18] and [19], which substitute the machine's shaft with a solid permanent magnet. A protecting enclosure is used to shield the PM and connect the shafts from both sides, as illustrated in Fig.…”

Section: Introductionmentioning

confidence: 99%

Design and Performance Investigation of 3-Slot/2-Pole High Speed Permanent Magnet Machine

Khan

et al. 2021

Self Cite

“…As the speed of the motor increases, the iron loss also increases, affecting the efficiency and reliability of the motor. Moreover, as the iron loss from the iron core increases, the temperature rises, and if the motor is driven in the DEF state for a long time, irreversible demagnetization of the permanent magnet in the rotor may occur due to overheating inside the motor [27][28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Fault Mechanism Analysis of Irreversible Demagnetization Due to the Dynamic Eccentricity of IPMSM for EV Traction

Kang

Hur

2022

The dynamic eccentricity fault (DEF) of the interior permanent magnet synchronous motor (IPMSM) is mainly caused by external mechanical shock. In the case of DEF, an unbalanced magnetic force occurs because the length of the air gap is not constant. Noise and vibration of the motor occur due to unbalanced magnetic force. In addition, since the length of the air gap is not constant, the distribution of magnetic flux density is distorted, and iron loss is increased. As the iron loss increases, the temperature rises, and an irreversible demagnetization fault (IDF) of the permanent magnet occurs due to overheating. Therefore, in this paper, the fault mechanism of IDF due to DEF of IPMSM for electric vehicle (EV) traction is analyzed. Initially, the magnetic flux density and iron loss characteristics according to the healthy condition and DEF condition are analyzed using the finite element method (FEM). Then, the detailed iron loss analysis is performed based on the phase current waveform measured through the load test of the motor. Finally, the fault mechanism of IDF due to DEF was verified through an electric-axle load test on a manufactured motor having eccentricity.INDEX TERMS Dynamic eccentricity, electric vehicle (EV), interior permanent magnet synchronous motor (IPMSM), iron loss, irreversible demagnetization.

“…The flux density of permanent magnets (PM) is related to motor design, PM materials and operating environment [1]- [3]. When a permanent magnet synchronous motor (PMSM) operates in the flux-weakening state, a large d-axis fluxweakening current is required at high speed, which decreases the flux density of PM and even causes PM irreversible demagnetization [4]- [6]. PM demagnetization will decrease the no-load back electromotive force (EMF) amplitude, increase the torque ripple and decrease the efficiency.…”

Section: Introductionmentioning

confidence: 99%

Design and Analysis of Permanent Magnets in a Negative-Salient Permanent Magnet Synchronous Motor

Zhao

Kou

et al. 2020

The Ld of a negative-salient permanent magnet synchronous motor (NSPMSM) is greater than Lq. When a NSPMSM is operating at or below the rated speed, the id is flux-intensifying current, which can improve the flux density of permanent magnets (PM). First, a NSPMSM is proposed and compared with a positive-salient permanent magnet synchronous motor (PSPMSM). The d-axis and q-axis equivalent magnet circuits of the NSPMSM are then established. According to the limitation of the equivalent magnet circuit, the PM dimensions formula and optimization of the finite element method (FEM), PM dimensions are determined, and the constant power speed ranges of the two motors are calculated. Second, the influence of the saliency ratio on the internal power factor angle and the average flux density of PM at different internal power factor angles are calculated. Third, the flux density of PM in two motors are calculated when the windings are short-circuited. Finally, the bypass function of the NSPMSM magnetic bridges during the flux-weakening state is analyzed. The results show that the flux-weakening magneto motive force (MMF) of the NSPMSM is smaller at high speed, the short-circuit current (SCC) is smaller when the windings are short-circuited, and the magnetic bridges protect the PM in the flux-weakening state, so the flux density of PM is larger.