Search

This work presents a novel speed sensor less air‐gap flux‐oriented vector control of dual stator induction generator (DSIG) used for grid connected, variable speed wind energy generation system. The DSIG consists of two stator windings electrically separated by an angle of 30° with dissimilar pole numbers, which are in the ratio of 1:3. This arrangement offers reduced magnetic core saturation and less harmonics in stator currents, which results into reduced stator winding losses. Moreover, presence of two stator windings makes DSIG suitable to be used in high power application. In conventional rotor‐flux‐oriented control, the rotor flux is oriented along the d‐axis of the rotor winding. But the rotor flux is not easily accessible. Air‐gap flux‐oriented vector control (AGFOVC) is advantageous as compared to conventional vector control because the air‐gap flux is easily accessible and does not require any special arrangement for the measurement of variables. Moreover incorporation of this novel speed sensor less air‐gap flux‐oriented vector control also eliminates the use of speed encoder as the rotor speed is estimated from the machine terminal variables. Elimination of speed encoder not only reduces the cost of the overall system but also nullifies the error due to mismeasurement of speed and enhances control flexibility and robustness. As a result of which robustness of the system increases. Here, two separate converters are used for the two stator windings of the machine. And the converter switching's are being performed by space vector‐based novel dwell time optimized 13‐zone hybrid PWM. This special PWM results in better harmonic performance, reduced torque pulsation, and minimal switching loss. The simulation of the overall system is performed in MATLAB environment and the simulated results are validated experimentally using dSPACE controller board DS1104. Close proximity in simulated and experimental waveforms justifies the effectiveness of the proposed work. [ABSTRACT FROM AUTHOR]

Summary: In this paper, an interior permanent magnet synchronous motor with a D‐type rotor configuration is presented. The performance of the proposed motor is compared with that of the widely used V‐type interior permanent magnet synchronous motor. For a fair comparison, all the motor parameters are identical. With the advent of different rotor topologies, multilayered and multisegmented permanent magnets are extensively used; however, an analytical modeling of D‐type interior permanent magnet synchronous motor has not yet been conducted. Furthermore, its analysis using the finite element method is considerably time‐consuming. To resolve this problem, an analytical method based on a magnetic equivalent circuit is proposed for the slotless D‐type interior permanent magnet synchronous motor. It is then compared with the finite element method at different pole arc–pole pitch ratios to demonstrate the effectiveness of the proposed method. Additionally, Schwarz‐Christoffel mapping is employed to maintain the slot shape and include the effect of adjacent slots by considering the slotting effect in the slotless air‐gap flux density. Finally, the presented motors are optimized based on the pole arc–pole pitch ratio to maximize the fundamental air‐gap flux density and minimize the total harmonic distortion. [ABSTRACT FROM AUTHOR]

In order to improve the air-gap flux density of the permanent magnet synchronous motor and reduce the cogging torque, a novel structure with asymmetric magnetic poles for automobile was proposed. Based on the characteristics of the parallel magnetic circuit, the magnetic flux path diagram is established. And the equivalent magnetic circuit model is established by the equivalent magnetic circuit method. The Taguchi method is used to be a multiobjective optimization algorithm. The total harmonic distortion of the air-gap flux density is the first optimization goal. The second and third optimization goals are the cogging torque and the average of output torque, respectively. And the torque ripple is a constraint condition. The optimized parameter combination is obtained by the Taguchi method. Finite element simulation analysis and prototype test are carried out for the optimized motor structure. The results show that the total harmonic distortion of air-gap flux density is reduced by 36.7% comparing with the initial structure. The cogging torque is reduced by 26.0%. And the average output torque is increased by 4.8%. [ABSTRACT FROM AUTHOR]

Summary: The structure of the rotor magnetic circuit has an obvious effect on the eddy current loss of the rotor of the high voltage line start permanent magnet synchronous motor. In this paper, a 10 kV to 1000 kW high voltage line start permanent magnet synchronous motor is taken as an example. The two‐dimensional electromagnetic field model of the motor with V‐shaped permanent magnet arrangement is established by using the finite element method. The no‐load back EMF and armature current of the motor are calculated, and the correctness of the model is verified. On this basis, this paper proposes a sector permanent magnet structure, compares the difference between the air gap flux density and the rotor eddy current loss of the two magnetic circuit structures, analyzes the advantages and disadvantages of the above magnetic circuit structure on the harmonic effect of the air gap flux density of the motor. The mechanism of the influence of different magnetic circuit structures on the eddy current loss of the rotor is revealed, which provides a reference for the design of a high voltage line start permanent magnet motor. [ABSTRACT FROM AUTHOR]

Summary: This article compares the 2‐D and 0‐D analytical models for the slotless double‐sided inner armature linear permanent magnet synchronous machines (SDSIALPMSMs). The sub‐domain method is implemented to achieve the 2‐D analytical model. In this method, the cross‐section of the motor is divided into eleven sub‐regions and the Maxwell equations are determined for each sub‐region. In the presented 0‐D model, a magnetic equivalent circuit (MEC) is derived to compute the maximum magnetic flux density in the air‐gap. In both approaches, the magnetic flux density is analytically calculated to predict the inductance, induced voltage, flux linkage and electromagnetic forces. Ultimately, the results of both analytical models are validated against those of the 3‐D finite‐element method (FEM) analysis. These results confirm the superiority of the 2‐D analytical model compared with that of the 0‐D in the terms of the accuracy of the magnetic flux density, induced voltage, self and mutual inductances as well as the tangential and normal electromagnetic forces. Also, less computational time of the described 2‐D analytical model is recognized as a merit compared with FEM models. [ABSTRACT FROM AUTHOR]

This paper investigates the radial stator vibration characteristics of turbogenerator under the static air-gap eccentricity (SAGE) fault, the rotor interturn short circuit (RISC) fault, and the composite faults (CFs) composed of SAGE and RISC, respectively. Firstly, the impact of the faulty types on the magnetic flux density (MFD) is analyzed, based on which the detailed expressions of the magnetic pull per unit area (MPPUA) on the stator under different performing conditions are deduced. Then, numerical FEM simulations based on Ansoft and an experimental study are carried out, taking the SDF-9 type fault simulating generator as the study object. It is shown that SAGE will increase the stator vibration at 2f (f is the electrical frequency) which already exists even in normal condition, while RISC and CF will bring in stator vibrations at f, 2f, 3f, and 4f at the same time. The vibration amplitudes under CF are larger than those under RISC. As SAGE increases, the vibration amplitudes of each harmonic component under CF will all be increased, while the development of RISC will decrease the 2nd harmonic vibration but meanwhile increase the 4th harmonic vibration. The achievements of this paper are beneficial for fault identification and condition monitoring of the turbogenerator. [ABSTRACT FROM AUTHOR]

Theoretical analysis and numerical FEM calculations, together with segmental experiment studies, are used to study the impact of the static air-gap eccentricity forms on the rotor unbalanced magnetic pull (UMP) of turbogenerator. The universal expression of the magnetic flux density under different forms of SAGE is firstly deduced, based on which the detailed UMP formulas for the normal condition and three SAGE cases are obtained, respectively. Then the exciting characteristics of the UMP for each SAGE form to generate vibrations are analyzed. Finally, numerical FEM calculations and segmental experiments are carried out to investigate the effect of SAGE forms on the rotor UMP, taking the SDF-9 type non-salient-pole fault simulating generator as the object. It is shown that, no matter what kind of SAGE occurs, amplitude increments at each even harmonic component of the UMP and the rotor vibration, especially the 2nd harmonic component, will be brought in. Meanwhile, the UMP keeps directing to the very position where the minimum radial air-gap is. Among the different SAGE forms, the rotor offset has the most sensitive effect on the rotor UMP and vibration, while the stator ellipse deformation has the weakest impact. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the effect of the axial air-gap eccentricity (AAGE) on the electromagnetic characters such as the axial unbalanced magnetic pull (UMP) and the electromagnetic torque (EMT). Firstly, the theoretical model of AAGE is set up, and the formulas of the axial UMP and EMT are deduced. Then the simulation study of a SDF-9 nonsalient pole synchronous generator is taken with Ansoft Maxwell to calculate the detailed axial UMPs and EMTs under normal condition and five AAGE conditions, respectively, with 2 mm to 10 mm rotor displacements. It is shown that an apparent axial UMP will be produced due to AAGE, while EMT and the phase current will be decreased. In addition, the magnetic flux density (MFD) on the stator end and the rotor end, which are more far from the center position of the stator core in the axial direction, will be decreased, while the MFD on the other ends will be generally kept stable. As AAGE develops, the axial UMP will be increased, while EMT and the phase current will be decreased. The proposed work offers a reference for the fault diagnosis and monitoring on AAGE. [ABSTRACT FROM AUTHOR]

A model to calculate arc temperature of air gaps discharge is presented in this article. Based on the energy balance equation, we obtained the mathematical method to evaluate the arc temperature. According to the model, arc temperature was calculated for two air gaps with different distance, respectively. The results showed that the peak arc temperature of 16.7 m air gap is 36 368°K, and the peak arc temperature of 10 m air gap is 34 277°K, which are in good agreement with the experiment results. The model built in this article can be used for lightning and switching impulse discharges in air gaps. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Summary: The efficiency of the motor is of paramount importance during selection and operation as well as energy consumption. In countries like India, international efficiency class (IE2) is versatile in use. Prominent efficiency improvements can produce very large energy savings across the country. Induction motors (IMs) are widely used for pump applications in India. IM exhibits high rotor (I2R) losses due to the presence of rotor current. This results in less efficient, more energy consumption compared with energy‐efficient motors. Energy‐efficient motor such has single phase direct‐on‐line synchronous reluctance motor (DOL‐SynRM) would be a right alternative for IM due to the absence of rotor current. DOL‐SynRM has been designed, optimized, and tested for a centrifugal pump application. Initially, single phase SynRM with capacitor start and capacitor run is modeled using equivalent circuit parameters and simultaneously simulated using MATLAB. The machine parameters like rib width, length, and thickness are optimized using genetic algorithm technique. The optimized rotor structures are taken to numerical analysis platform for performance prediction. The flux distribution, moment of inertia, air gap flux density, the effect on the inductances, starting torque, average torque, and torque ripple are thoroughly investigated using this analysis. The high‐efficiency rotor structure is fabricated and configured with a centrifugal pump. Experimental results reveal that the overall system efficiency has been improved compared with the existing induction motor. Moreover, thermal analysis is carried out for two types of frame structures (conventional and proposed) to study the hot spot in the proposed motor. [ABSTRACT FROM AUTHOR]