A novel method for cogging torque reduction in permanent magnet brushless dc motor using tshaped bifurcation in stator teeth m. Rotorside cogging torque minimization methods are examined in detail with major focus on magnet. This paper presents the method for reducing cogging torque in surfacemounted. Variation of peak cogging torque with slot number in 2pole motor. Cogging torque reduction in surfacemounted permanent. There are several methods for the reduction of cogging torque such as segmented permanent magnet 1, ux barrier employed in rotor structure 2, the continuum sensitive analysis combined with the fem for rotor structure.
Cogging torque is one of the most important parameters of permanent magnet motors, which causes torque ripple, vibration and noise. Cogging torque reduction in permanent magnet brushless motors. Paper open access methods for reducing cogging torque in. First of all, its characteristic and parameter dependency should be thoroughly. Magnetic pole shape optimization of permanent magnet motor. Therefore, the reduction of the cogging torque becomes a major concern for electric motor designers. Cogging torque is an internal pm generator feature that depends on generators geometry. Reduction of cogging torque in permanent magnet fluxswitching machines. Reduction of cogging torque, harmonics in pm bldc motor. One of the rotor yoke and the permanent magnet ring is an annular member including depressed portions along a peripheral edge located around a midpoint between each pole.
This torque is position dependent and its periodicity per revolution depends on the number of magnetic poles and the. The method by which cogging torque was reduced to a level suitable for direct coupled sawes has been implemented during prototype fabrication. This torque is position dependent and its periodicity per revolution depends on the number of magnetic poles and the number of teeth on the stator. In a permanent magnet generator, cogging torque is produced due to interaction of the rotor. Paper open access methods for reducing cogging torque. Available literatures mainly focused on its general design procedure and performance analysis. In this paper, the design for an electromagnetic structure and reduction cogging torque of a dual stator structured radial flux permanent magnet generator, which is a combination of the inner and.
Whats the difference between cogging torque and torque ripple. The method pole of width modulation reducing cogging. The impact of slots with different sizes on the fourier coefficients of relative airgap permanence function is demonstrated. Cogging torque is an important issue in design of permanent magnet motors, especially in certain high accuracy applications. It is apparent that the cogging torque reduction can reach about 50%. Research article reduction of cogging torque in dual rotor. Analytical modeling of the cogging torque in permanent magnet. Permanent magnet synchronous machine for calculation of cogging torque. Various techniques have been devised to minimize cogging torque, out of which two approaches bifurcation and slot opening methods have been focused in this paper. Cogging torque in permanent magnet motors precision microdrives. Article pdf available in iop conference series earth and environmental science 1942. Konghirun, a study of cogging torque reduction methods in brushless dc motor, ecti transactions on electrical engineering electronics communications vol.
Unlike other motors, an ipmsm uses a permanent magnet to create magnetic field, and cogging torque generally occurs in the motor owing to the. Cogging torque reduction in permanent magnet machines. In a permanent magnet generator, cogging torque is produced due to interaction of the rotor magnets with slots and teeth of the stator. This paper studies properties and reducing techniques of cogging torque in brushless motors with surface permanent magnets and winding slots. This paper describes the mechanism of cogging torque, introduces several methods of reducing cogging torque and points out the advantage of novel magnet arrayed permanent magnet motor in reducing cogging torque. The key features of bldc machines include high starting torque density and extending speed range, though the cogging torque is a threat for its performance. Almost all the techniques used against cogging torque also reduce the motor counterelectromotive force and so reduce the. In many machines, where permanent magnets are used, the effects due to cogging torque generated by permanent magnets pms aggravate the output characteristics of the machines. Desirable combination between stator slots and magnet poles, and relation between the slots and added notches are shown. A comparative analysis of cogging torque reduction in bldc. Pdf cogging torque reduction for interior permanent. Pdf methods for reducing cogging torque in permanent magnet. This calculating technique is called hybrid method. Reduction of cogging torque in permanent magnet flux.
Cogging torque in a permanent magnet motor, which arises from the interaction of the rotor magnets with the steel teeth on the stator, can be reduced by skewing the stator teeth, but only at the expense of added complexity in stator construction and some loss of output torque. Cogging torque reduction in a permanent magnet wind turbine generator preprint january 2002 nrelcp50030768 e. This paper presents the use of taguchi methods in optimizing a pmsm for reducing peak value of cogging torque. Cogging torque makes a noise and vibration in the motor speed. Reduction of cogging torque in dual rotor permanent magnet generator for direct coupled wind energy systems sivachandranpaulsamy department of electrical and electronics engineering, sree sastha institute of engineering and technology, chennai, india correspondence should be addressed to sivachandran paulsamy. Cogging torque reduction in permanent magnet machines luke dosiek, studentmember,ieee, and pragasen pillay, fellow,ieee abstractthis paper examines two methodsmagnet shifting and optimizing the magnet pole arcfor reducing cogging torque in permanent magnet machines. Cogging torque reduction in a permanent magnet wind. Cogging torque reduction in a permanent magnet wind turbine. Interior permanent magnet synchronous machines show a good range of behaviours, which make these kinds of machines good candidates for an electromechanical energy conversion. Reduction of cogging torque in permanent magnet synchronous motor using the taguchi method p. Methods for reducing cogging torque in permanent magnet. Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets of the rotor and the stator slots of a permanent magnet pm machine.
A novel method for cogging torque reduction in permanent. Table ii factor c for typical 2pole brushed pm motors with overlapping windings all edges of magnets would face slot openings. Analytical prediction of cogging torque for interior permanent. Cogging torque reduction for interior permanent magnet. Afpmsm is proposed which reduces the motor cogging torque.
Reduction of cogging torque in dual rotor permanent magnet. Kavya abstracta variety of techniques are available to reduce cogging torque in permanent magnet brushless dc pmbldc motors. Many authors proposed different methods for analysis and reduction of cogging torque 2, 3, 12. The fea concerned with determination of cogging torque, reduction of cogging torque, and determination of induced emf was performed using magnet software. Aalborg universitet an analytical equation for cogging torque. Cogging torque reduction methods are discussed and applied to the optimum design of a small brushless dc motor. Several approaches have been developed to attempt minimizing the cogging torque of permanent magnet motors, such as stepped skewing of permanent magnet blocks 2, modifying permanent magnet arc 3, 4, providing.
Methods for reducing cogging torque in permanent magnet synchronous motors. In this paper, magnetic field analysis was conducted on brushless motors with radially oriented ring magnets to find effective ways to reduce cogging. Cogging torque reduction by magnet pole pairing technique 110 interaction. The utility of pmbldc machines is extending its tentacles in industrial arena. Cogging torque reduction of interior permanentmagnet. Pdf methods for reducing cogging torque in permanent. Design and experimental analysis for reduction of cogging. Of permanent magnet and hybrid types, hybrid steppers have higher detent torque due to their toothed rotors, which allows them to better manage the magnetic. Pdf cogging torque reduction in brushless motors by a. Cogging torque reduction of ipm motor using skewing, notching.
A novel pm shape for reducing cogging torque in afpmsm. Influence of design parameters on cogging torque in. Reduction of cogging torque in permanent ma gnet motors abstract. Engineering and manufacturing airturbines equipment and supplies equipment performance evaluation synchronous motors mechanical properties torque control wind turbines. Cogging torque reduction by magnet pole pairing technique. Cogging torque in a permanent magnet motor, which arises from the interaction of the rotor magnets with the steel teeth on the stator, can be reduced. Cogging is an undesirable characteristic of some permanent magnet motor designs. Reduction of cogging force is one of the main concerns of tubular permanent magnet linear motor tpmlm. Thus the efficient performance of the motor can be calculated by the reduction of cogging torque and harmonics present. The key to the development and application of the pmiwm consists in the improvement of its control accuracy and dynamic performance. Andreas binder institute of electrical energy conversion department of electrical engineering and information technology technical university of darmstadt landgrafgeorgstr.
Introduction permanent magnet pm motors have been an invaluable part of the industry today as these motors can save nearly any industry a great deal of time and money under the right circumstance. Analysis of torque ripple and cogging torque reduction in. Reduction of cogging torque in doublerotor axialflux. However, in order to improve their accuracy in their torque responses, the cogging torque and torque ripple phenomena should be mitigated to obtain better performance of the machine. Cogging torque reduction of ipm motor using skewing. Influence of design parameters on cogging torque in permanent. In addition, an analytical calculation of cogging force is deduced by the energy method. Current harmonics controller for reduction of acoustic. In this paper, finite element method fem is taken to analyze various design techniques to reduce the cogging torque in a prototype 1210pole pmfsm. An exact analytical description of the magnetic field in idealized models of surface mounted permanent magnet motors is presented.
This paper presents the method for reducing cogging torque in surfacemounted permanent magnet synchronous motor spmsm. Cogging torque reduction in surfacemounted permanent magnet. Pdf new cogging torque reduction methods for permanent. New cogging torque reduction methods for permanent magnet. Performance optimization of permanent magnet synchronous. In this method, the desired torque decreases because less magnet. Cogging torque reduction and o set of dualrotor interior. In a permanent magnet motor, cogging torque arises from the interaction of the rotor magnets with the steel teeth on the stator. Pdf cogging torque reduction for interior permanent magnet. Permanent magnet and hybrid stepper motors, which use a permanent magnet rotor, exhibit detent torque. Reducing cogging torque in surfacemounted permanent magnet motors by nonuniformly distributed teeth method article in ieee transactions on magnetics 479.
The taguchi optimization method was used to generate the experiment samples, which were calculated in 2d and 3d fea. A study of cogging torque reduction methods in brushless. In wind energy systems employing permanent magnet generator, there is an imperative need to reduce the cogging torque for smooth and reliable cut in operation. Cogging force reduction for tubular permanent magnet linear. A method for reducing cogging torque of integrated. This paper presents several costeffective magnetskewing techniques to minimize cogging torque components in doublerotor afpm motors. Cogging torque reduction in line start permanent magnet. The analytical model of cogging torque is derived by the energe method.
Cogging torque, which arises from the variation of the magnetic field energy stored in the air gap, 3 is a drawback of permanent magnet motors. Us6784582b1 magnet shaping and pole concentration for. Cogging torque reduction of interior permanent magnet. The impact of slots with different sizes on the fourier coefficients of relative airgap permanence function is. In this paper, an analytical calculation of airgap magnetic density is derived. The rotor is rotated in a fraction of the slot pitch and the resulting torque was calculated.
Reducing cogging torque in surfacemounted permanent. Reduction of cogging torque in permanent magnet synchronous. A rotor for a permanent magnet motor with a rotor yoke and a permanent magnet ring mounted on the rotor yoke, the magnet ring having a plurality of circumferentially spaced poles. An approximate closed form solution is derived therefrom. Such a technique is performed for the reduction of cogging torque in bldc motors 5. Permanent magnet motors are generally used for eps but a reduction of cogging torque in these motors is one of the challenges we face to ensure safe and comfortable vehicle handling. There are several methods for the reduction of cogging torque such as segmented permanent magnet 1, ux barrier employed in rotor structure 2, the continuum sensitive analysis combined with. A study of cogging torque reduction methods in brushless dc motor 147 cogging torque by designing either magnet width or magnet length decreased. References 1 dosiek, luke, and pragasenpillay 2007. Cogging torque has influence on the starting torque, it creates noise and vibration. Ghassemi, cogging torque reduction optimization in surfacemounted permanent magnet motor using magnet segmentation method, electric power components systems vol. Influence of design parameters on cogging torque in permanent magnet machines 409 fig. Green to be presented at the 21st american society of mechanical engineers wind energy symposium reno, nevada january 1417, 2002 national renewable energy laboratory 1617 cole boulevard golden, colorado 8040393. Reduction of cogging torque in permanent magnet motors.
As to the cogging torque results obtained from measurements, finite element calculations, exact and approximate analytical modeling are compared with each other. Special magnet positioning or magnet pole width manipulation can be also taken into account and the resultant cogging torque wave of the modified machine can be calculated in a short time. Cogging force reduction for tubular permanent magnet. It can be shown that in a motor having full polepitched magnets the. This paper is a result of an ongoing research work that deals with various methods to reduce cogging. Cogging torque reduction and o set of dualrotor interior permanent magnet motor in electric vehicle traction platforms myeonghwan hwang 1, haesol lee 2,3, sehyeon yang 2,4, gyeseong lee 2,3, jongho han 2, donghyun kim 1,2, hyeonwoo kim 2 and hyunrok cha 2, 1 department of electrical engineering, chonnam national university, 77. Analytical method for calculation of cogging torque reduction due. Whats the difference between cogging torque and torque. Its also known in stepper motors as detent or no current torque. Because the cogging torque has a close relation with the distribution of the magnetization, the magnetizing system for permanent magnets is analyzed numerically by using the timestepping finite element method. This work addresses the problem of mitigating the effects of the cogging torque in permanent magnet synchronous motors, particularly brushless motors, which is a main issue in precision electric. Cogging torque reduction in pmsm motor by using proposed new.
Reduction of cogging torque in permanent magnet motors ieee. Cogging torque is generated when the sides of the rotor teeth line up with the sides of the stator teeth within the motor. Cogging torque reduction in a permanent magnet wind turbine generator pdf. Analysis and reduction of cogging torque of linestart permanent magnet motors libing jing, jun gong, and ying lin abstractcompared with a standard permanent magnet synchronous motor, a linestart permanent magnet synchronous motor lspmsm has additional features that include twosided slots on its stator and rotor.
Introduction the phenomenon of cogging torque is an intrinsic characteristic of permanent magnet synchronous motors pmsms, in both interior ipm and surfacemounted spm electric machine types. Permanent magnet motors and generators have one common problem in operation it is cogging torque. Howe, influence of design parameters on cogging torque in permanent magnet machines, ieee transactions on energy conversion vol. Cogging torque reduction of permanent magnet synchronous. In figure 4, a comparison of the normalized cogging torque between uniform air gap and nonuniform air gap breadloaf magnet shape is shown. Cogging torque reduction for interior permanent magnet synchronous motors submitted on. Reduction of cogging torque in permanent magnet fluxswitching machines yu wang 1, jianxin shen, weizhong fei 2, zongxifang 1college of electrical engineering, zhejiang university, hangzhou, 310027, china, 2department of aerospace power and sensors. Minimizing cogging torque in designing axialflux permanentmagnet afpm motors is one of the main issues which must be considered during the design process.
The suggested is the optimization of an anisotropic ferrite magnet shape and magnetization. Pdf reduction of cogging torque in permanent magnet flux. Cogging torque reduction in brushless motors by a nonlinear. Cogging torque reduction in pmsm motor by using proposed. Decoupling control for permanent magnet inwheel motor. Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets of. For the inner rotor motor, the halbach array can reduce the magnetic flux. Three different parameters of pmsm, such as skew ratio, pole embrace and stator slot width. Analytical modeling of the cogging torque in permanent. Design and experimental analysis for reduction of cogging torque by pole shifting in permanent magnet synchronous generator. Permanent magnet fluxswitching machine pmfsm is a relatively new structure. The permanent magnet inwheel motor pmiwm is anonlinear, multivariable, strongly coupled and highly complex system. Most of the methods utilized for cogging torque reduction lead to motor structure complexity, increasing manufacturing cost and also influencing the output torque. Methods for reducing cogging torque in permanent magnet synchronous.