1,720,981 research outputs found
A numerical design platform for induction motor efficiency enhancement under cost and performance optimization constraints
No full text
Optimal Selection of Rotor Bar Number in Multiphase Cage Induction Motors
Full text linkRules for the selection of rotor bar numbers which minimize current and torque ripples are derived in this paper for a general symmetrical multiphase cage induction machine with prime phase number and integral slot winding. Analytically obtained expressions for optimal rotor bar number selection are validated by means of totally independent simulations, one based on a parameterized winding function (PWF) model of the induction machine and the other employing time-stepping finite element analysis (TSFEA). As a case study, five-phase four-pole cage induction motors with forty stator slots and different number of rotor bars are comparatively analyzed. Results obtained from the PWF model are in excellent accordance with those independently obtained by TSFEA and both confirm the correctness of the proposed selection criteria. The practical motivation of the study is that an incorrect selection of rotor bar number can lead to parasitic torques of significant amplitude and, presently, there are no general rules available in the literature which may guide designers towards an optimal design choice for a general number of phases
Regenerative testing of a concentrated-winding permanent-magnet synchronous machine for off-Shore wind generation - Part II: Test results
No full textPotentials and limits of three-phase fractional-slot concentrated winding optimization
No full textFractional-slot concentrated windings (FSCWs) in three-phase permanent magnet machines are popular for several advantages but may cause severe performance issues due to their richness in air-gap magneto-motive force (MMF) space harmonics. This paper intends to explore the potentials and limits of FSCW optimization through multi-layer arrangements when applied to mitigate three problems, namely: permanent-magnet eddy-current losses, unbalanced magnetic pull (UMP) and torque ripple. It shows that, regardless of the algorithm adopted, the winding optimization is effective only on well-defined slot-pole combinations, which are strongly different depending what the optimization target is. Permanent magnet loss minimization is shown to be the field where the most effective results can be achieved, while UMP and torque ripple can be mitigated by winding optimization to a smaller extent and for a limited set of slot-pole combinations
Investigation into Multi-Layer Fractional-Slot Concentrated Windings with Unconventional Slot-Pole Combinations
Full text linkFractional-slot concentrated windings (FSCWs) are an attractive option for the design of synchronous permanent-magnet machines. It is commonly assumed in the existing literature that a symmetrical three-phase FSCW is feasible only on a condition that the number of slots Z is an integer multiple of three times the maximum common divisor between Z and the number of pole pairs p. Slot-pole combinations satisfying this rule can be defined conventionally, the others unconventionally. In contrast to the common belief, this paper shows that, using a multi-layer arrangement, it is possible to synthetize a symmetrical FSCW having unconventional slot-pole combinations. A general design methodology for this purpose is presented and validated by finite element analysis. The pros and contras of FSCWs with unconventional slot-pole combinations are examined. Finally, the application of an unconventional FSCW to a shipboard surface permanent-magnet machine prototype is presented to illustrate the possible practical convenience of this kind of winding and tests on the prototype are reported for experimental validation
Optimal Selection of Rotor Bar Number for Minimizing Torque and Current Pulsations due to Rotor Slot Harmonics in Three-Phase Cage Induction Motors
Full text linkThe paper develops a method to choose the number of rotor bars in order to eliminate rotor slot harmonics in stator current spectrum and pulsation torques that are their consequence. Mains-fed, three-phase cage induction motors with the most common number of pole pairs and number of stator slots, that result in integer slot winding, are analyzed. The analysis is based on the recently derived general rule for optimal selection of rotor bars, valid for symmetrical multiphase machine with prime number of phases and integer slot stator winding. As a tool for validation of analytically predicted results, parameterized winding function (PWF) model is used. Electromagnetic torque ripple factor is used as a measure of goodness of the number of rotor bar selection. The practical motivation of the study is an attempt to supersede the many existing rules for rotor bar number selection that, depending on the source, may be different, and provide a unified general approach to the problem. One of the main findings derived in the paper is ascertainment that increasing the number of pole pairs increases the degree of freedom in choosing the proper number of rotor bars. The same applies when the number of motor phases increases
Fast Computation Method for Stator Winding Skin-Effect Additional Losses in Synchronous Machines with Open Slots and Arbitrary Rotor Geometry
No full textLarge medium-voltage electric machine stators are usually equipped with form wound coils made of flat conductors (strands) and embedded in open (rectangular) slots. Air-gap magnetic flux lines can enter the slot and, sweeping the strands placed nearest the slot opening, induce eddy currents in them. Such eddy currents cause additional losses which can be much higher than usual skin-effect and proximity losses. In order to avoid dangerous overheating and hot spots, the additional losses in question need to be carefully predicted in the design stage. Time-stepping finite-element analysis (TSFEA) can be used for the purpose, which however implies a large computational burden and requires the machine geometry to be modeled in detail. This article proposes alternative methods based on time-harmonic finite-element analysis (THFEA) simulations performed on highly simplified machine models and with no need to take rotor motion into account. The proposed methods are shown to produce very accurate results, compared to TSFEA, but with very significant time and computational savings
A system level approach to the optimal dimensioning of induction motors variable-frequency drives
No full textOptimal Rotor Bars Number in Four Pole Cage Induction Motor with 36 Stator Slots - Part I: Numerical Modeling
No full textThe identification of the optimal number of rotor bars in grid-fed, four-poles, three-phase cage induction motor is addressed in this two-part work for the frequent case of 36 stator slots. The optimization criterion being adopted is the minimization of the electromagnetic torque pulsations in full-load steady-state conditions. In Part I of the work results from the parameterized winding function (PWF) model are presented and successfully validated against time-stepping finite element simulations. In Part II the electromagnetic torque pulsations obtained from the PWF model are evaluated for different numbers of rotor bars. During this process motor rated power, stator winding design and main machine geometry are maintained invariant. The evaluation is applied to both possible practical cases of unskewed rotor bars and rotor bars that are skewed by one stator slot pitch
- …
