Stator Structure Research Articles

Mathematical modeling of a novel bearingless switched reluctance motor

Purpose – The novel bearingless switched reluctance motor (BSRM) is proposed recently, which is different from the conventional BSRM in the stator structure and suspension winding arrangement. The reduced number of suspension windings makes the novel BSRM much simpler, so that the control circuit and algorithm are greatly simplified when compared to those of the conventional BSRM. This paper for the first time proposes the novel BSRM's analytic model, including the mathematical relationships among the winding currents, rotor angle, radial forces, and motor torque, to further achieve the suspending forces and torque control. The paper aims to discuss these issues. Design/methodology/approach – The magnetic equivalent circuit method is employed to obtain the self-inductances and mutual-inductances of the motor torque windings (main windings) and suspension windings (control windings). The straight flux paths are combined with the elliptical fringing flux paths to calculate the air-gap permeances, and the stored magnetic energy. Then, the mathematical expressions of radial forces and torque are derived. A novel BSRM prototype is analyzed through using the proposed analytical model and the finite element model. The results of both methods are compared to verify the proposed mathematical model. Findings – The proposed mathematical model of the novel BSRM considering unsaturated magnetic circuits is verified by finite-element analysis results. Research limitations/implications – The mathematical model represents the situation of magnetic circuit unsaturated and is not suitable for the magnetic circuit saturation. It cannot be used to control the motor which is working in the deep magnetic circuit saturation region. Practical implications – Building mathematical model is a necessary step for the motor's suspension and rotating control. The built model provides the fundamental for the preliminary control algorithm and experimental study of this novel BSRM. Originality/value – For the first time, the novel BSRM's mathematical model is proposed. It provides necessary fundamental for the motor's further analysis, design, and suspending and rotating controls.

A Design Study of Dual-Stator Permanent Magnet Brushless DC Motor

Dual - stator permanent magnet brushless DC Motor (DSBLDC) feature s high efficiency and torque - densit y . As DSBLDC could operate in various states according to different winding connection modes , it is fully qualified for electric vehicle (EV) drive. Unfortunately, due to the particular dual - stator structure, th is kind of motor is difficult to be design ed by available design methods. However, this paper demonstrates that a DSBLDC with series magnetic circuit structure can be regarded as being consisted of two independent BLDCs , an inner-rotor BLDC and an outer-rotor BLDC. Thus, the DSBLDC can be divided into two single-stator BLDCs. Based on this demonstration, the design method is verified by finite element analysis (FEA) , and the basic design steps are given. Furthermore , experimental result s of the prototype motor have verif ied the correction of the method, which also indicates that the motor with superior performance is adapted to EV drive.

A Driver for the Single-Phase Brushless DC Fan Motor With Hybrid Winding Structure

This paper mainly proposes a novel driver for a single-phase brushless dc fan motor with a hybrid series/parallel winding structure. The winding symbols and directions of the hybrid motor stator structure are defined, and the winding steps for the proposed series/parallel winding are explained. An adequate inverter driving circuit, which is capable to simultaneously obtain the advantages of the hybrid structure, is also discussed. At last, the overall system of this hybrid brushless dc motor with the proposed driving circuit is then implemented to verify the performance of the proposed driver and structure.

A Novel Wind Power Generator System with Automatic Maximum Power Tracking Capability

This paper presents a novel off-grid wind power generator system that consists of a permanent magnet (PM) generator, two rectifiers, a battery, and loads. The PM generator has a novel stator structure and two Y-connected winding sets. The wind power generator system can automatically track the maximum power from wind without the need for converters and control circuits, and has higher reliability and lower loss. This paper also describes the operational principle and mathematical model of the system. A prototype is manufactured, and experiments prove that the new system efficiently captures maximum power from wind across a wide speed range.

Characteristics of the Linear Piezoelectric Motor with Semi-Elliptical Stator

A novel design of the semi-elliptical motor based on a double-mode type ultrasonic motor is proposed and analyzed in this paper. Due to the simplification, the semi-elliptical piezoelectric motor can be considered as an improvement of the elliptical piezoelectric motor which we have proposed in the past. The composite structure of the stator in the motor is formed by two multilayer piezoelectric actuators clamped in a semi-elliptical elastic body. In the simulation, finite element modeling of the motor is performed. The geometry of the stator has been computed with the help of the finite element analysis. Then, the dimensions of the stator's structure were determined by making the two resonance frequencies close to each other. In the experiments, the impedance and the displacement response are measured and discussed for understanding the characteristics of the linear piezoelectric motor with a semi-elliptical stator. The motor achieved maximum moving speed of 96 mm/s and the maximum output force of 0.64 N when applying a sine wave of 14Vr driving voltage at 21.2 kHz, while the maximum moving speed of 132 mm/s and the maximum output force of 0.88 N can be achieved if applying two signal driving method of the same voltage.

Comparison of a High Thrust Force Density Segmental Stator Linear Switch Reluctance Machine for with Different Topologies

Linear switch reluctance machine (LSRM) has been an alternative to linear permanent magnet synchronous machine and linear induction machine. However, the nature of reluctance force production, together with the air gap which is always much larger than rotary SRM, result in low propulsion force density in LSRM. This is an inherent demerit of LSRM, limiting its applications where the machine size is strictly set. This paper presents a novel linear switch reluctance machine with segmental stator, which consists of series of ferrite-magnetic segments. The principle of the proposed LSRM featuring high force density has been introduced. A variety of topologies of the proposed machine have been presented including single stator, dual stator and non-stator yoke structure. This paper deals with the comparison of the proposed segmental stator linear switch reluctance machine and traditional teeth type linear reluctance machine in terms of the propulsion force, normal force and force ripple as well as the force density and active pay load ratio. Finite Element Method is implemented to obtain the correlated results. Some conclusions are drawn to verify the analysis above.

An Active Vibration Control Strategy to Prevent Nonlinearly Coupled Rotor–Stator Whirl Responses in Multimode Rotor-Dynamic Systems

This brief describes an active control method to prevent unwanted nonlinear vibration response modes of a rotor-dynamic system. Nonlinear stiffness of components that support or surround a machine rotor can cause a response branch that extends critical vibration (resonance) over a wide interval of rotational speeds. Within this interval, jump transitions between alternative low amplitude and high amplitude response modes become possible. This brief explains how such behavior can be eliminated by applying control forces to the rotor based on dynamic feedback of strains measured in the stator structure. An optimal model-based controller synthesis is considered that combines a Lur'e-type Lyapunov function with a quadratic cost measure to penalize controller gain and bandwidth. Results are presented for an experimental flexible rotor system where nonlinear rotor-stator interaction occurs through a bearing with radial clearance. An active magnetic bearing applies control forces to the rotor in a separate plane. The results show that the control technique can eliminate jump response modes and can significantly reduce mechanical stress associated with rub interaction of the rotor and stator. The influence of key parameters in the model and controller formulation is shown.

A Novel Two-Phase Permanent Magnet Synchronous Motor Modeling for Torque Ripple Minimization

This paper proposes a novel two-phase, two-pole, permanent magnet synchronous motor (PMSM) with dual U-core stator structure for torque ripple minimization. The proposed motor is modeled based on the conventional single-phase U-core PMSM with approximate output power and core dimension. Torque ripple in the novel motor can be reduced significantly due to 90 $^{\circ}$ electrical angle phase shift in two sets of magnet pairs and 90 $^{\circ}$ shift in two-phase excitation currents. Characteristics of both PMSMs such as back-EMF, cogging torque and electromagnetic torque are analyzed and compared by using the 3-D finite element analysis (FEA). As shown in the result, the cogging torque and torque ripple in the novel two-phase PMSM are efficiently reduced with sinusoidal back-EMF waveform and reasonable current density value. The validity of both PMSM models is also verified by the comparison between simulated and experimental measured results.

Design and Analysis of in-Wheel Permanent Magnet Synchronous Motor Cooling System of Mining Dump Truck

In-wheel motor is an important power unit of electric drive mining trucks, a variety of dynamic performance and thermal issues have important impacts on the whole vehicle performance. In this paper, a model of permanent magnet brushless DC motor (BLDC) cooling system with water-cooled stator structure of electric drive mine dump truck is built. Considering the actual cooling systems, the author modeled the bldc motor and completed the electromagnetic simulation with ansoft software to determine the motor heat source and boundary conditions. This paper simulates the cooling water jacket temperature field with fluent software, and finally validated the feasibility of the design of the motor and its cooling system by experiments.

Design Techniques for Reducing Cogging Torque in SPM Motors Using Shifted Slot Opening

Skewing is one of the most common methods to reduce the cogging torque of permanent magnet synchronous motors. This technique may cause manufacturing troubles such as impossible automatic slot filling due to skewing stator slot. One method to overcome this problem is to use the step twisted stator structure with shifted slot opening. Compared to other methods of skewing, in the presented method, the stator slots are still straight slots and the skewing effect is implemented by shifting slot openings coupled with a step twisted stator design. This paper discusses the use of the step twisted stator structure with shifted slot opening and the associated effects on machine performance. We address the cogging torque, average torque, torque ripple, and back-EMF and its total harmonic distortion (THD). We examine the results using finite element analysis (FEA).

ELECTROMAGNETIC DESIGN AND FEM ANALYSIS OF A NOVEL DUAL-AIR-GAP RELUCTANCE MACHINE

The electro-magnetic torque production in the reluctance machine is highly in∞uenced by the magnetic linkages in the air-gap area. The conventional machines derive the drawback of reduction in the air-gap area to a minimal due to in∞uence of mechanical unbalancing thereby restricting the efiective energy conversion area. In order to increase the magnetic linkage area, the dual-air-gap structure is introduced. The dual-air-gap structure is realised through the division of the magnetic circuit area into two air-gaps while still maintaining the net air-gap length value. A double-rotor with single- stator structure is used to attribute the above concept. The electro- magnetic analysis of such a structure is developed and investigated through numerical analysis. In order to validate the proposed structure the electro-magnetic characteristics are compared with that of the conventional structure at similar operating conditions. The maximum torque generated by the selected dual-air-gap structure is 1.7549Nm and for conventional structure is 1.2723Nm. The evaluation of the proposed machine is done at the same operating conditions and it is found that the dual-air-gap structure exhibit 65% increase in average torque value in comparison with that of the conventional single-air-gap structure.

Torque ripple minimization and maximum power point tracking of a permanent magnet reluctance generator for wind energy conversion system

A permanent magnet reluctance generator (PMRG), which is the member of switched reluctance machine (SRM) family, has an extremely simple and robust structure: no winding on both rotor and stator. Required flux for energy conversion is provided by magnets buried in stator yokes. Thus, it seems to be suitable for wind energy conversion systems (WECSs) for reducing power generation cost to the level of fossil energy conversion systems. In a PMRG based conventional WECS, the PMRG is often accompanied by a simple diode bridge and a maximum power point tracking (MPPT) controlled converter. This type of converter topology does not allow utilizing any torque ripple minimization strategy. Thus, the system inevitably suffers from large torque ripples due to the doubly salient structure of both stator and rotor of the PMRG. Torque ripples propagate acoustic noise, vibrations, and mechanical stress in the turbine-shaft. Exposing to such ripples may result serious failure or damage in the WECS. In this paper, a novel algorithm consisting of MPPT and torque ripple control has been tested on the PMRG based WECS. The control strategy is applied to the system through an asymmetric half bridge (AHB) converter which is accepted to be a traditional converter for SRMs. The performance of control method has been verified under the conditions of constant and variable wind speed. Both simulation and experiment results prove that the control algorithm with the AHB converter allows significant torque ripple reduction in PMRG based WECS while generating power at its maximum point.

Enlargement of the Claw Pole Motor using SMC Cores Divided in the Direction of a Circumference

Claw teeth motors have a feature that can make axial the length thin. This makes them suitable for appliances, automobile assistant machines, and small-sized industrial motors. On the other hand, there is a need to thin HEVs, elevators and large-sized industrial motors. In this study, we examined a higher output of the claw teeth motor. We arrived at the following conclusions as a result of our research. 1) The optimal stator structure was determined and the prospect of attaining the specification of 123N·m was determined. 2) A manufacturing subject called core assembly accuracy reservation, thin coil manufacture, and the rotator insertion method became clear. 3) The experimental results and the analysis results were in agreement with respect to the EMF. 4) The experimental cogging torque results and FEA results are in agreement in the 6th degree. But the 2nd and the 4th degrees of the experimental cogging torque results did not agree with the FEA results. 5) Although the core needed to be divided in the direction of the circumference for enlargement, it was clear that the influence on the torque is small. 6) Division of the core is a good solution for enlargement of the claw teeth motor.

Effect of Stator Structure and Field Analysis of a New Type Single-Phase Induction Motor

The new type single-phase induction motors with three stator windings are brought forward for there high efficiency and low cost. However, the unbalance current density in the stator windings is still a problem to the design of this type motor. This paper presents the asymmetrical stator windings and slots structure in the motor design to get the currents density balance. A magnetic field analysis of the new type tri-winding induction motor is preformed using a two-dimensional finite element method. The Maxwell stress method is used to compute the air gap torque that is required for solving the equation of motion. The perfomance of the motor with different structure stator are compared and analysised.

MODELLING AND ANALYSIS OF A PIEZOELECTRIC ANNULAR STATOR STRUCTURE FOR A NEW IN-SITU DYNAMIC BALANCE REGULATOR

This paper presents the modelling and analysis of a piezoelectric annular stator structure for a new in-situ dynamic balance regulator which is driven by the in-plane bending vibration of the stator. The mathematical model for the in-plane vibration is first developed using an analytical method to determine the theoretical excitation frequency. The excitation modes and structural parameters are then analysed to optimise the performance of the stator. To improve the efficiency of the design and to achieve precise control, a semi-analytical electromechanical coupling model is developed using the dynamic substructure method and the finite element method. The model is verified in preliminary tests.

Switching Algorithm for Maglev Train Double-Modular Redundant Positioning Sensors

High-resolution positioning for maglev trains is implemented by detecting the tooth-slot structure of the long stator installed along the rail, but there are large joint gaps between long stator sections. When a positioning sensor is below a large joint gap, its positioning signal is invalidated, thus double-modular redundant positioning sensors are introduced into the system. This paper studies switching algorithms for these redundant positioning sensors. At first, adaptive prediction is applied to the sensor signals. The prediction errors are used to trigger sensor switching. In order to enhance the reliability of the switching algorithm, wavelet analysis is introduced to suppress measuring disturbances without weakening the signal characteristics reflecting the stator joint gap based on the correlation between the wavelet coefficients of adjacent scales. The time delay characteristics of the method are analyzed to guide the algorithm simplification. Finally, the effectiveness of the simplified switching algorithm is verified through experiments.

Synchronous whirl mode maps for rotor vibration with stator interaction across clearance annuli in multiple planes

For rotating machines having rotor–stator structures with non-linear stiffness characteristics or finite clearances between rotor and stator parts, there can be a multiplicity of possible vibration behaviours for any given operating speed. When the dynamic characteristics of the machine structure possess rotational symmetry, possible vibration modes arising due to unbalance can be calculated exactly from the frequency response of the structure. This study extends current theory by considering systems for which rotor–stator contact interaction may occur in multiple transverse planes. Damping and friction effects arising from contact mechanics are also accounted for. The model equations can be used to compute a complete set of vibration solutions involving circular whirl and thereby establish parametric regions where a low amplitude whirl can transgress to a high amplitude one with rotor–stator contact in one or more planes. Experimentally identified whirl modes for a flexible rotor system interacting with two clearance bearings show a good correlation with the theoretical predictions and thus indicate the suitability of the approach as a tool for prediction and design. The results are pertinent to the design of magnetic bearing and auxiliary bearing systems but are also relevant to a wide range of machines where rotor vibration may exceed clearance limits or boundaries of linearity.

Theoretic and Experimental Approach to the Adoption of Bonded Magnets in Fractional Machines for Automotive Applications

This paper aims to tackle the general problem of increasing the performances of small permanent-magnet (PM) machines, through the use of bonded magnets instead of the more diffused ferrite magnets. In particular, the study is developed for a fractional-slot concentrated winding PM machines for automotive applications. Neodymium bonded magnets with different and unconventional resins are realized in the internal laboratories. The rotors with the different magnet technologies are experimentally characterized, and the experimental values are compared with the simulation ones. The obtained results allow to define the possible performance increment. Finally, this paper analyzes the possible improvement of the rotor magnetic circuit for a better exploitation of the bonded magnets, without altering the stator structure and the motor housing.

Adaptive Neuro-fuzzy Controller for Multi-layered Switched Reluctance Motor

ABSTRACT There has been big interest in switched reluctance motor (SRM) due to its simplicity and reasonable cost, however excessive torque ripple is one of the major disadvantages of switched reluctance motor. This paper attempts to reduce torque ripples of Switched Reluctance Motor through building multi-layered motor controlled by a hybrid intelligent system known as Adaptive Neuro-fuzzy Inference System ANFIS. Simulation of the proposed motor is conducted using Matlab Simulink environment 2011 and comparison results with single layer switched reluctance motor for both PI and ANFIS controllers show improvement in behavior of MSRM controlled by ANFIS through reduction in speed settling time as well as torque ripples. General Terms Electrical Machines; Adaptive Control. Keywords Rodrigues et Multi-layer switched reluctance motor; SRM; Torque ripples; ANFIS. 1. INTRODUCTION SRM has received attention due to its inherent simplicity, ruggedness, and low cost. These features make it a good candidate for various general purpose adjustable speed applications [1]. The most unique feature of SRM is its double saliency structure which means both stator and rotor has salient poles. The stator winding has concentrated coils, and shorter end turns than other types of motors, leading to a greater manufacturing economy. Moreover the salient rotor has no conductors or magnets, as shown in fig. 1. The rotor turns to get to a position of minimum reluctance by aligning itself with the stator magnetic field when the stator windings are excited, it is thus considered as the simplest of all electric machine rotors[1],[2]. Simplicity of the construction of SRM makes it inexpensive, the windings are electrically separate from each other which make the machine reliable, and cooling is simpler because the major sources of heat are on the stator. In addition, high speed capability of SRM and high torque to inertia ratio makes it a superior choice in different applications. However, Excessive torque ripple, especially at low speeds prevented SRM from widespread use [3]. Actually there are two approaches to reduce torque ripples: one of them is to improve the magnetic design of the motor, by changing the stator and rotor pole structures [4]. El-Kharashi [5] used the hollow cylindrical rotor to reduce torque ripples. There was no shaft, and the cylindrical rotor was designed to grade the air gap, and consequently the reluctance; which reduced ripples in the torque characteristic. Shang and Shing [6] changed the stator shape to c- shape one, the c-shape created more space for winding and hence became more straightforward, it had more number of turns per phase than traditional SRM; as a result the motor gave higher torque for the same current than in traditional SRM and consequently, minimize the cost of the motor. Daldaban and Ustkoyuncu [7] introduced multi-layer SRM. Their design allowed more space for stator winding and higher starting torque than classical SRM of the same size. The noise was reduced as well as torque ripples. The second approach is to use sophisticated electronic control. The electronic approach is based on selecting an optimum combination of the operating parameters, such as supply voltage, turn on and turn off angles and level of current [4]. al. [8] implemented fuzzy logic controller for reducing torque ripples through turn off angle. Zhang et al. [9] also used fuzzy controller to compute the current compensating signal that added to the main current value in order to reduce torque ripple. While Shang et al. [10] introduced flux-linkage controller using sliding mode technique (SM) with integral compensation (I). The integration of SM with I controller result in reduction of torque ripples when compared to each method alone.

Design and analysis of variable reluctance resolver for hybrid-electric vehicle

In order to realise the high precision control in the motor and drive system of hybrid-electric vehicle, it is necessary to test the rotor position and motor speed in real-time. The main sensors used for testing the rotor position and motor speed are photoelectric encoder and resolver. The resolver is gaining wide acceptance due to its reliable mechanical structure and ease of integration with motor systems. This paper mainly studies the important parameters of the resolver including the structure of stator and rotor, the influence of air-gap length by rotor shape, the winding way of exciting output winding, deduces the formula of back-EMF, carries out dynamic experiment on resolver and presents the waveform of back-EMF under working status.