High-speed PM Research Articles

AC Copper Loss Evaluation Method for High-Speed PM Motors with Rectangular Coils

AC Copper Loss Evaluation Method for High-Speed PM Motors with Rectangular Coils

Comprehensive Performance Analysis of High-Speed PM Motors With Layered Rotor Structures

Comprehensive Performance Analysis of High-Speed PM Motors With Layered Rotor Structures

Badania przyczyn niepożądanej synchronizacji prędkości obrotowej silnika z częstotliwością modulacji PWM w układzie napędowym PM BLDC

In a drive system comprising a high-speed PM BLDC motor and an inverter implementing motor phases commutation and phase voltages PWM modulation, a spontaneous synchronisation between the PWM modulation frequency and the motor rotational speed may occur. The drive behaves like an unintended phase-locked loop. The effect distorts mechanical characteristic of the drive by introducing flat segments where the rotational speed remains constant despite changing load torque. It makes the speed-torque relationship discontinuous, nonlinear, and non-unique. The phenomenon is closely related to the problem of phase current and motor torque ripples. The paper presents experimental results recorded with a laboratory test bench for drives for electric power tools where the phenomenon of the parasitic speed locking has been observed. A root cause of this effect is discussed, and the mechanism of unwanted synchronisation is investigated. Several mitigation techniques are proposed and verified with computer simulations.

Multiphysics Comparative Study of High Speed PM Machines for Ring PM Rotor and Solid PM Rotor

This paper presents a comprehensive comparison of ring PM rotor and solid PM rotor for high speed permanent magnet machines (HSPMMs) by considering the multiphysics performance, including the rotor stress, electromagnetic characteristics, loss characteristics, thermal characteristics, and rotor dynamics. Firstly, six rotor schemes with different rotor structures and different sleeve materials are designed for a 10 kW, 100 000 rpm ultra HSPMM. Secondly, the multiphysics characteristics of six rotor solutions are compared one by one through the corresponding finite element model, including the rotor stress, electromagnetic and loss characteristics, temperature distribution and rotor dynamic. Finally, based on the above analysis, the final rotor design parameters are determined. A prototype is manufactured and tested to verify the theoretical analysis.

Analysis of losses in the high-speed PM BLDC motor with open slot stator core made of amorphous soft magnetic material

PurposeThe purpose of this paper is to verify results related to losses in the core of a brushless DC prototype motor, obtained using its computer FE models, by experimental tests on manufactured machines. The paper focuses on the comparison of losses in the core of a machine with a classical stator core made of an iron–silicon material (Fe–Si) and a new one made of a modern METGLAS material.Design/methodology/approachComputer models of the prototype motors were created using FEM. The designed machines were manufactured, and experimental tests were performed. To achieve high frequencies in rotating magnetic fields, motors with a stator to rotor pole ratio of 9/12 were built. Twin rotor approach was applied, as two identical rotors were built along the two geometrically identical stators made of different core materials.FindingsExperimental studies have shown the superiority of the METGLAS material over the classical Fe–Si material. Material parameters were measured directly on the prepared cores as library data used in the simulation may be incorrect due to technological processes during core production, which was also verified. Problems related to twin rotor approach have been identified. Solution to the problem has been suggested. Necessity of 3D FEM modelling was identified.Originality/valueThe main source of originality is that METGLAS material used in the prototype machines was developed and manufactured by the authors themselves. Original approach to core parameter evaluation based on simplified methodology has been suggested. Another original part is a simplified methodology applied to loss measurement during no-load test.

Surrogate Model-Based Multiobjective Optimization of High-Speed PM Synchronous Machine: Construction and Comparison

This article employs surrogate models for large-scale high-speed (HS) electrical machine optimization to reduce heavy computational burden caused by the finite-element method (FEM) based on nondominated sorting genetic algorithm II. Three artificial neural networks, namely, multilayer perceptron (MLP), support vector regression (SVR), and generalized regression neural network (GRNN), and the classical Kriging model are developed based on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> -fold crossing validation method. To find out the most suitable surrogate model, a HS permanent magnet synchronous machine (PMSM) applied in electrically assisted turbocharger (EATC) considering its multiphysics characteristics is optimized by different models. A detailed comparison is provided in terms of prediction accuracy and modeling time consumption. The optimal design is verified to guarantee the accuracy of optimization results. The key contributions of this article include an automatic HSPMSM optimization process is proposed, where complete modeling and tuning method as well as a reasonable comprehensive evaluation metric of different surrogate models are conducted. It is found that invalid samples from the initial dataset contain useful information to improve prediction accuracy. Hence, an entire surrogate process should benefit from a pretrained classifier. Also, it reveals that MLP, SVR, and Kriging model can greatly improve the design optimization effectiveness with high accuracy, whereas GRNN is not suitable for this specific optimization scenario.

Analysis of alternating flux density harmonics inside the rotor of a 1 MW high-speed interior permanent magnet synchronous machine used for flywheel energy storage systems

With the popularization of renewable distributed energy generation in the power grid, flywheel energy storage systems (FESS) with fast response and high power density are gradually becoming popular for achieving fast frequency modulation. Generally, the rotor of high-speed permanent magnet synchronous machine (HSPMSM) used for FESS rotates in a vacuum to reduce air friction loss, which concurrently makes it difficult to dissipate heat in the rotor. For reducing rotor iron loss and preventing demagnetization of the PM due to high temperature, effective measures need to be applied. In this study, a 1 MW 10,500 r/min high-speed interior PMSM (HSIPMSM) is proposed for an FESS. As rotor iron loss is caused by alternating flux density harmonics (FDH) inside the rotor, the causes and characteristics of alternating FDHs are analyzed. Then, the finite element analysis (FEA) is combined with two-dimensional fast Fourier transform (2D-FFT) to obtain the alternating frequencies and amplitude variation trends of alternating FDHs in the designed rotor. The analytical results indicate that the amplitudes of alternating FDHs on the PM surface are effectively reduced due to bypass of the rotor core at the outside of the PM to alternating FDHs, which helps to restrain the rotor iron loss from the source. This provides a design idea for mitigating the high temperature of high-power high-speed PM rotors.

Design and Analysis of the High-Speed Permanent Magnet Motors: A Review on the State of the Art

This paper provides an overview of the design and analysis of high-speed PM motors by focusing on prominent issues such as motor losses, temperature rise, rotor strength and vibration. The design challenges of high-speed PM motors are briefly described, and the application of various stator and rotor structures and materials is presented in electromagnetic design. Combined with the temperature distribution of the motor, various heat dissipation measures to suppress the temperature rise are summarized. Strength and dynamics analysis of the rotor are outlined with respect to the safety of rotor operation. The current status of coupled multi-physics domain design used to improve the comprehensive design capability of high-speed PM motors is reviewed. Future directions of technologies related to the design of high-speed PM motors are pointed out.

Comprehensive Analysis of the AC Copper Loss for High Speed PM Machine With Form-Wound Windings

The skin effect and proximity effect at high frequencies would greatly increase the AC copper loss of high speed permanent magnet machines (HSPMMs), especially for form-wound windings. However, the influence of some factors on the AC loss of the form-wound winding is still unclear in the existing research. Therefore, this paper presents comprehensive research on the AC copper loss of HSPMM with form-wound windings. Firstly, the model of eddy current field considering the skin effect and the proximity effect for form-wound windings is established, and the AC losses of each stator slot and each conductor at high frequency are obtained. In addition, the factors affecting the AC loss are comprehensively analyzed through the eddy current field, including the conductor size, the number of conductors per slot, and the operating temperature. Furthermore, the influence of strand wire sizes on temperature distribution of HSPMM is also implemented by establishing a temperature calculation model. Finally, the theoretical results are verified by testing the AC resistances of five coils at different frequencies and the temperature characteristic of an HSPMM prototype with form-wound windings.

Outer-Rotor-type High-Speed PM motor with Segmented-shaped Rotor

Outer-Rotor-type High-Speed PM motor with Segmented-shaped Rotor

Design Guidelines and Scaling Effects for Bearingless PM Synchronous Machines Accounting for Eddy Current Reaction Field

Apart from mechanical constraints, the maximum size and output power of high-speed bearingless PM synchronous machines is mainly limited by two effects with disturbing influence on the bearing force vector. One is the interference between the stator drive field and the suspension air gap field. The other one is the air gap field deformation by rotor eddy currents due to the asynchronously rotating stator field wave, which generates a non-moving bearing force vector. The eddy current reaction field lowers the bearing force amplitude and leads to a spatial error angle. Apart from material properties, these two effects are mainly influenced by the split ratio and the permanent magnet height. It is discussed how the machine's main dimensions and pole count shall be chosen in order to keep the influences of these effects small. It is also shown how the motor efficiency suffers from these effects and how the corresponding limitations vary with machine size and electromagnetic utilization.

Prototype Tests of Outer-Rotor-type High-Speed PM Motor

Prototype Tests of Outer-Rotor-type High-Speed PM Motor

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

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.

Influence of Stator Gap on Electromagnetic Performance of 6-Slot/2-Pole Modular High Speed Permanent Magnet Motor With Toroidal Windings

The 6-slot/2-pole (6s/2p) permanent magnet motors with a diametrically magnetized PM rotor are popular for high speed application. Meanwhile, toroidal winding can not only reduce end-winding length but also eliminate unbalanced magnetic force for short axial length motors. Therefore, the electromagnetic performance of a 6s/2p high speed PM (HSPM) motor with toroidal windings is firstly analyzed, including air-gap flux density, flux linkage, back-EMF, cogging torque and electromagnetic torque. Then, considering modular design for auto-manufacturing, the influence of stator gap and misalignment on the electromagnetic performance is investigated. It shows that the stator gap results in unbalanced three phase back-EMFs, not only amplitudes, but also phase angles. The stator gap increases the equivalent air-gap length and PM flux leakage, which leads to lower air-gap flux density, back-EMF, and average torque. Moreover, the stator gap results in asymmetric air-gap length, which results in large cogging torque. Further, it shows that the misalignment of two stator parts mainly affects the uneven equivalent air-gap length and symmetry of winding configuration, which leads to unbalanced three phase back-EMFs, especially phase angles, and self- and mutual-inductances, as well as rotor PM loss. Experimental results of a prototype motor with/without stator gap and/or misalignment are given to validate the finite element predicted analyses.

They do it with lasers

New high-speed PM laser deposition technology could dramatically improve the wear resistance of mechanical parts. Liz Nickels spoke to a German-based research institute about its innovative EHLA process.

Asymmetric Bar Winding for High-Speed Traction Electric Machines

A new asymmetric bar winding concept along with the analysis and benefits for high-speed traction electric machines is presented. The objective is to reduce the ac losses, especially at high speeds, utilizing optimized and asymmetric conductor heights within a slot for bar-wound stators. Detailed winding diagram, height optimization, ac loss analysis, and thermal performance are presented for both symmetric, i.e., conventional, and asymmetric bar windings. The proposed idea is validated using the closed-form analytical equation and 2-D time-stepped finite-element analysis (FEA). A substantial reduction of ac losses and improvement in continuous power over the wide operation range is achieved as demonstrated for a 12-pole, 100-kW high-speed (15 000 r/min) PM traction machine. Thermal performance analysis using forced liquid cooling is also included. The design and analysis methodology is presented to support high-speed traction electric machine designers meet the ever-increasing demand on efficiency and performance with bar-type windings.

Efficiency Improvement of Outer-Rotor-type High-Speed PM Motor

Efficiency Improvement of Outer-Rotor-type High-Speed PM Motor

Reduction of Rotor Harmonic Eddy-Current Loss of High-Speed PM BLDC Motors by Using a Split-Phase Winding Method

Low-order harmonic currents in high-speed permanent magnet brushless dc (PM BLDC) motors cause large rotor eddy-current loss, resulting in high temperature rise and even overheating in the rotors, thus their application in the field of high-speed drive is limited. The rotor eddy-current loss can be reduced by using a split-phase winding method. In this paper, various time–space orders of harmonic eddy-current losses in the rotors of the PM motors with and without split-phase winding are quantified. The calculated results indicate that the rotor harmonic eddy-current losses generated by the low-order harmonic currents, which inherently exist in PM BLDC motors, are greatly reduced. Furthermore, associated with the characteristics of harmonic currents of PM BLDC motors, the mechanism of drastically reducing the rotor harmonic eddy-current loss of high-speed PM motors by using the split-phase winding method is revealed and experimentally validated.

Theoretical and experimental researches of active magnetic bearing systems for high-speed PM machines

Theoretical and experimental researches of active magnetic bearing systems for high-speed PM machines

Effects of Teeth Length and Magnet Material on Characteristics and Effects on Conductor Eddy Current Loss due to Changes in the number of Strands of Litz Wire of Low Voltage Drive High-Speed Motorp

High-speed motor driven in low voltage are used in equipment such as electric reel and handy vacuum cleaner. If a motor with a general structure used in an operating range of several thousand revolutions is used as it is in a high-speed range of several tens of thousands of revolutions, efficiency will decrease due to a large amount of iron loss. In this paper, we proposed models in which the stator teeth length and the magnet material were changed in order to suppress the iron loss that causes the efficiency reduction of the high-speed PM motor. In this case, since the eddy current loss occurs in the armature conductor, the effect of reducing the conductor eddy current loss by using the Litz wire was also examined. As a result, it was shown that the proposed model improves the efficiency compared to the conventional structure.