Design techniques for cogging torque reduction in a fractional-slot PMBLDC motor

2020 ◽  
Vol 39 (5) ◽  
pp. 1041-1055
Author(s):  
Lidija Petkovska ◽  
Paul Lefley ◽  
Goga Vladimir Cvetkovski
Keyword(s):  
Torque Ripple ◽  
Simple Design ◽  
Electromagnetic Torque ◽  
Arc Length ◽  
Original Design ◽  
Cogging Torque ◽  
Content Type ◽  
Motor Design ◽  
Fractional Slot ◽  
Design Techniques

Purpose This paper presents the design techniques applied to a novel fractional-slot 6/4 pole permanent magnet brushless direct current (PMBLDC) motor, for cogging torque reduction. The notable feature of this motor is the simplicity of the design and low production cost. The purpose of this paper is to reduce the peak cogging torque of the motor. The focus is put on the stator topology tuning, and a new design for the stator poles is proposed. By determining the optimum stator pole arc length and the best pole shoe thickness, the cogging torque is significantly reduced. This new optimised motor design has been analysed in detail. The validation of the results is documented with respective figures and charts. Design/methodology/approach At the beginning, the design data for the 6/4 pole PMBLDC motor with concentrated three phase windings and asymmetric stator pole arcs is presented. In the study, this motor is taken as a reference model (A0, T0). A full performance finite element analysis of the reference motor has been carried out, and the weak points in the motor design have been identified. By simple design techniques, tuning the stator pole geometry, a two-stage design optimisation for cogging torque minimisation has been performed and the solution array has been derived. The optimised model is selected and proposed (Aopt, Topt). The comparative analysis of the reference and optimised motors show the advantages of the proposed novel design and prove the methodology. Findings The results of the work demonstrate how simple design techniques can minimise the peak of the cogging torque profile, while maintaining the specified electromagnetic torque value. The sensitivity of the cogging torque profile because of changes of the stator pole design inside the prescribed constraints is apparent. The stator poles of the reference motor have an arc length of 85° and pole shoe thickness of 6 mm. The newly shaped stator poles have an arc length of 78.5° and pole shoe thickness 4.8 mm. The peak-cogging torque has been reduced from 0.158 Nm to a respectable value of 0.066 Nm. However, to reduce electromagnetic torque ripple and pulsations, further investigations are required. Originality/value The paper presents an approach to cogging torque reduction for a 6/4 PMBLDC motor. A two-step original design procedure is introduced and an optimised stator pole geometry is defined. The minimised cogging torque has been demonstrated with improved usage of the active materials. This work could serve as a good basis for further optimisation of the motor design.

Multi-objective optimization of a spoke-type permanent magnet motor with fractional-slot concentrated windings for EVs

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Suying Liu ◽  
Jinlin Huang
Keyword(s):  
Optimization Design ◽  
Torque Ripple ◽  
Electrical Machine ◽  
Multi Objective Optimization ◽  
Content Type ◽  
Driving System ◽  
Torque Density ◽  
Multi Objective ◽  
Lower Torque ◽  
Fractional Slot

Purpose This paper aims to propose a spoke-type fractional-slot concentrated windings (FSCW) PM machine for EVs driving system to improve torque density. To further improve electromagnetic performance, the multi-objective optimization design is processed based on response surface (RS) model and simulated annealing cuckoo search (SA-CS) algorithm. Design/methodology/approach The spoke-type FSCW PM machine is designed and optimized to meet the requirement of EVs driving system. First, a spoke-type FSCW PM machine is designed and some of key parameters are obtained based on equivalent magnetic circuit (EMC) method. Then, the RS model and modified SA-CS algorithm are proposed to obtain higher torque, lower torque ripple and higher efficiency. Findings After verification by finite element method for no-load and load performance, the optimal machine has higher torque density, lower torque ripple and higher efficiency compared with initial machine. Finally, a 20 kW prototype is manufactured and tested to verify the validity of the proposed optimization design method. Originality/value This paper designs a high torque density spoke-type FSCW PM machine, which is superior for EVs driving system. Meanwhile, a novel modified SA-CS algorithm is applied to the field of electrical machine multi-objective optimal design.

Analysis of electromagnetic torque for induction motors with a novel non-skewed rotor structure

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Amir Darjazini ◽  
Abolfazl Vahedi ◽  
Amin Nobahari ◽  
Saber Gharehseyed
Keyword(s):  
High Performance ◽  
Induction Motors ◽  
Acoustic Noise ◽  
Torque Ripple ◽  
Iron Loss ◽  
Mechanical Equipment ◽  
Electromagnetic Torque ◽  
Content Type ◽  
The Mean ◽  
Rotor Structure

Purpose Pulsating torques cause a number of problems in electrical machines, including mechanical vibrations, acoustic noise and the depreciation of mechanical equipment. In induction motors, the slot skewing method is an effective way to solve these issues; however, it has some drawbacks such as output torque drop, stray loss intensification due to inter-bar currents and iron loss increment. Besides, slot skewing may not be practical in higher-rated induction motors. In this regard, this paper introduces a modified non-skewed rotor (MNSR) structure as a possible alternative to the skewed designs. Design/methodology/approach The proposed structure includes a two-segmented rotor with an intermediate ring between the rotor parts that are mounted on the shaft with a relative shift angle. Detailed information about the idea and structure of the MNSR as well as its manufacturing aspects will be presented in the second section of the paper. First, the working principle of the proposed design is described via analytical equations to provide an insight into the concept. The shifting angle will then be calculated by analyzing the harmonic contents of the electromagnetic torque. Finally, the validity of the analytical method will be verified by developing three-dimensional finite element models. Findings It is demonstrated that by using the proposed rotor structure, the torque ripple has been reduced to a satisfactory level without significantly affecting the mean torque, unlike the skewing method. Furthermore, the new method could avoid the disadvantages of the skewing method while enhancing other motor characteristics such as iron loss. Also, the total volume of the MNSR is equal to the initial design, and the mass and material differences are also negligible. Originality/value In this paper, a MNSR is introduced as a possible alternative to the skewed patterns. The study mainly focused on electromagnetic torque profile characteristics, i.e. the mean torque enhancement and the ripple reduction. The MNSR structure can be used for general purposes and high-performance applications, especially where excellent torque characteristics are required.

scholarly journals Study of the Synchronous Reluctance Motor Design

2016 ◽  
Vol 53 (4) ◽  
pp. 22-29 ◽  
Author(s):  
J. Dirba ◽  
L. Lavrinovicha ◽  
R. Dobriyan
Keyword(s):  
Magnetic Flux ◽  
Torque Ripple ◽  
Electromagnetic Torque ◽  
Synchronous Reluctance Motor ◽  
Reluctance Motor ◽  
Motor Design ◽  
Twofold Decrease ◽  
External Rotor

AbstractThe paper focuses on studying the external-rotor synchronous reluctance motor. The analysis is performed to estimate the influence of the number of stator slots and non-magnetic areas in the rotor (i.e., flux barriers) on the electromagnetic torque and torque ripple of the studied motor. It is concluded that the increase in the number of stator slotsZ= 6 toZ= 18 causes an approximately twofold decrease in the ripple factor, but torque increases by 5 %. Electromagnetic torque will be increased approximately by 24 %, if non-magnetic flux barriers are created in the rotor of the studied synchronous reluctance motor.

Direct Torque Control for a Bearingless Induction Motor Based on Model prediction

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ding Wang ◽  
Zebin Yang ◽  
Xiaodong Sun ◽  
Weiming Sun ◽  
Haitao Mei
Keyword(s):  
Phase Angle ◽  
Direct Torque Control ◽  
Torque Ripple ◽  
Torque Control ◽  
Electromagnetic Torque ◽  
Flux Linkage ◽  
Content Type ◽  
Voltage Vector ◽  
Space Voltage Vector ◽  
Stator Flux

Purpose The purpose of this paper is to address the large stator flux linkage ripple and electromagnetic torque ripple caused by the hysteresis comparator in traditional direct torque control for a bearingless induction motor (BIM). Design/methodology/approach Model predictive direct torque control (MPDTC) strategy is adopted. On the basis of the mathematical model of BIM, the stator current and stator flux observational values are obtained, and the electromagnetic torque and stator flux at the next moment are predicted. Then, based on the relationship between the stator flux and the electromagnetic torque, the predicted stator flux can be transformed into an equivalent flux linkage vector, which eliminates the weighting coefficients problem among multiple variables in traditional objective functions. The objective function and torque PI controller will output the optimal stator flux linkage and the increments of the torque phase angle. Through the phase angle increments, the space voltage vector can be obtained by the reference flux linkage controller instead of the stator flux linkage and the torque hysteresis controller. Findings The proposed MPDTC method can effectively improve the stator flux linkage and the torque ripple. It can implement the stable suspension of the rotor and improve the dynamic performance and steady-state accuracy of the BIM system. Originality/value A MPDTC strategy is proposed to reduce the ripple of stator flux and electromagnetic torque. The phase angle increment angle of stator flux linkage and electromagnetic torque is optimized by model prediction, and the optimal space voltage vector is obtained by designing the reference flux controller.

Optimal design of spoke type motor and magnetizer using FEM and RSM

2018 ◽  
Vol 37 (2) ◽  
pp. 730-739
Author(s):  
Young Hyun Kim ◽  
Jung Ho Lee
Keyword(s):  
Optimal Design ◽  
Mass Production ◽  
Permanent Magnets ◽  
Design Method ◽  
Cost Effective ◽  
Torque Ripple ◽  
Efficient System ◽  
Cogging Torque ◽  
Content Type ◽  
Type Motor

PurposeThis study aims to propose criteria for both optimal-shape and magnetizer-system designs to be used for a high-output spoke-type motor. The study also examines methods of reducing high-cogging torque and torque ripple, to prevent noise and vibration.Design/methodology/approachThe optimal design of the stator and rotor can be enhanced using both a response surface method (RSM) and finite element method (FEM). In addition, a magnetizer system is optimally designed for the magnetization of permanent magnets for use in the motor.FindingsThe criteria not only improve performance but also reduce manufacturing costs. The criteria are verified FEM together with an RSM. These methods are used to optimize the stator and rotor shape and the magnetization system. These methods allow us to produce an efficient system for mass production of the motor.Originality/valueThis study proposed a design method that uses rare earth magnets in a system to replace the spoke-type IPM. To verify the optimal design, torque characteristics were analysed using FEM and RSM. Excellent results were achieved regarding the reduction of cogging torque and torque ripple. In addition, the design of the magnetizer enables a cost-effective mass production system for the motor.

Torque ripple analysis for IPM AC motors

2014 ◽  
Vol 33 (5) ◽  
pp. 1514-1526 ◽  
Author(s):  
Jianxin Shen ◽  
Dan Shi ◽  
Canfei Wang ◽  
Peng Li ◽  
Kang Wang ◽  
...  
Keyword(s):  
Torque Ripple ◽  
New Method ◽  
Element Analysis ◽  
Cogging Torque ◽  
Content Type ◽  
Ac Motors ◽  
Ac Motor ◽  
Interior Permanent Magnet ◽  
Novel Method ◽  
Irregular Variation

Purpose – The purpose of this paper is to investigate a new cause of torque ripple in interior permanent magnet (IPM) alternating current (AC) motors, which is common but has hardly been studied. The paper also proposes a new method to suppress the total torque ripple. Design/methodology/approach – Besides the well-known cogging torque and mutual torque ripple, a new ripple which exists in the reluctance torque is found. It is verified with both analytical model and finite element analysis. Also, a novel method is proposed to reduce the reluctance torque ripple, with experimental validation. Findings – It is usually said that the winding inductances of an IPM AC motor vary sinusoidally with the rotor position, thus, the d-axis and q-axis inductances are constant, whilst the reluctance torque is smooth. However, in most practical motors, the inductances vary irregularly, causing a significant ripple in the reluctance torque. Moreover, in machine design, it is always desirable to suppress the cogging torque as much as possible. However, in this paper, it is proved that the cogging torque can remain and be used to cancel the reluctance torque ripple. Originality/value – Torque ripple in the IPM AC motors is usually reduced by suppressing the cogging torque and making both back electromotive forces and currents sinusoidal. However, this paper reveals the new cause of the torque ripple due to the irregular variation of winding inductances. Moreover, the paper gives a new method to cancel the reluctance torque ripple with the cogging torque.

Torque and back-emf in hybrid excited claw pole generator

2018 ◽  
Vol 37 (4) ◽  
pp. 1342-1353 ◽  
Author(s):  
Marcin Wardach
Keyword(s):  
Permanent Magnets ◽  
Experimental Results ◽  
Original Design ◽  
Element Analysis ◽  
Simulation Research ◽  
Cogging Torque ◽  
Content Type ◽  
Excitation Coil ◽  
New Construction ◽  
Torque Values

Purpose The paper aims to present the hybrid excited claw pole generator design, simulation and experimental results. The prototype has claw poles on two rotor sections, between which an excitation coil is located. The innovation of this machine is permanent magnets location on claws of one part of the rotor. The paper presents construction of the machine and analysis of the current in the excitation control coil influence on the electromagnetic torque, cogging torque and back-emf values. Presented studies enabled the determination of the torque and the back-emf for both: the strengthening and the weakening of magnetic field. Design/methodology/approach In the study, finite element analysis was used to perform simulation research. Then, based on the simulation studies, an experimental model was built. The paper also presents selected experimental results. Findings Achieved results show that the proposed machine topology allows to eliminate the disadvantages mentioned in paper, i.e. necessary to introduce special areas inside the machine to limit magnetic flux leakage or its complicated construction. Research limitations/implications The obtained cogging torque values and back-emf pulsation are still relatively high. In the near future, some of known techniques for reducing these pulsations can be applied, including the use of magnetic wedges, changing shapes of rotor’s poles and/or skewing of permanent magnets. Practical implications The proposed solution can be used in wind turbines as a generator. Originality/value The paper presents an original design of a new construction of a hybrid-excited claw pole machine and also an excitation current influence on cogging torque and back-emf values.

scholarly journals Electromagnetic Torque Improvement of Doubly Salient Permanent Magnet Machine Using Pole Ratio Adjustment Technique

2021 ◽  
Vol 9 ◽  
Author(s):  
Warat Sriwannarat ◽  
Pattasad Seangwong ◽  
Apirat Siritaratiwat ◽  
Nuwantha Fernando ◽  
Yuttana Dechgummarn ◽  
...  
Keyword(s):  
Torque Ripple ◽  
Open Circuit ◽  
Load Test ◽  
Optimal Structure ◽  
Electromagnetic Torque ◽  
Cogging Torque ◽  
Doubly Salient ◽  
Rotor Poles ◽  
Conventional Machine ◽  
Flux Path

This paper introduces the pole ratio adjustment technique to improve the torque characteristics of the doubly salient permanent magnetic machine (DSPM). The electrical characteristics of the machine, namely the magnetic field distribution, flux linkage, back-electromotive force (EMF), and cogging torque, were obtained under open-circuit conditions. The electromagnetic torque and ripple torque were examined under the loaded condition. The simulations, based on the 2D-finite element method, show that the optimal pole ratio for the DSPM structure is with 18 stator teeth and 15 rotor poles. This optimal structure achieves a larger phase back-EMF than the conventional structure, as well as had a better magnetic flux path with a reasonable cogging torque. The on-load test also confirmes that the proposed optimal structure can produce a significantly higher electromagnetic torque than the conventional machine while maintaining a satisfactory torque ripple. Furthermore, an experimental prototype of the DSPM structure having 18/15 stator/rotor poles was fabricated and tested to verify the simulations. The experimental results were in good agreement with the simulations. The design technique and the fabricated prototype demonstrate the DSPM utilization for low-speed/high torque applications.

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