• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.148-153
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• 2004

This paper represents that parts of a large generator operating in 1000 MW are affected by centrifugal forces due to high-speed rotation in 3600 rpm and 3D FEM Analyses are required to obtained the structural reliability of the generator. From these results, one would know the weakest locations and the stress distributions. The fatigue life is calculated in order to grasp the remaining life of generator. 2D and 3D analyses are performed to calculate stresses of the generator rotor and the retaining ring. From 2D results, we find the SCF at the slot and sub-slot of the rotor. 3D analysis is applied at the end part of generator rotor, which represents complex geometry, and rotor and retaining ring shrink thermally. With these results, designers of rotor and retaining ring can compare with the results of design code and verify the stress distributions of generator rotor and retaining ring, and then calculate the remaining life from the low-cycle fatigue data.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.595-602
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• 2015

The rotor configuration of the brushless doubly fed induction generator (BDFIG) plays an important role in its performance. In order to make the magnetomotive force (MMF) space vector in one set rotor windings to couple both magnetic fields with different pole-pair and have low resistance and inductance, this paper presents a novel wound rotor type for BDFIG with low space harmonic contents. In accordance with the principles of slot MMF harmonics and unequal element coils, this novel rotor winding is designed to be composed of three-layer unequal-pitch unequal-turn coils. The optimal design process and rules are given in detail with an example. The performance of a 700kW 2/4 pole-pair prototype with the proposed wound rotor is analyzed by the finite element simulation and experimental test, which are also carried out to verify the effectiveness of the proposed wound rotor configuration.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.196-201
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• 2008

This paper is about electromagnetic vibration source in outer rotor type of BLDC motors. Experiments are carried out with three pole-slot combinations which are 6 slots, 12 slots, and 24 slots with 4 poles rotor. According to results, vibration sources separate into electromagnetic and mechanical factors. Using the finite element method (FEM), It is analyed that vibration characteristics of electromagnetic source in each type. This paper shows electromagnetic sensitivity to vibration, and introduces necessary point in lower vibration motors. Also rotor balance is important to prevent uneven distribution of magnetic flux between rotor and stator.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권3호
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• pp.272-276
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• 2005

This paper deals with the method to calculate the rotor eddy current losses of permanent magnet high-speed machines considering the effects of time/space flux harmonics. The flux harmonics caused by the slot geometry in the stator is calculated from the time variation of the magnetic field distribution obtained by the magneto-static finite element analysis and double Fast Fourier Transform. And, using the analytical approach considering the multiple flux harmonics and the Poynting vector, the rotor losses is evaluated in each rotor composite. Using this method is simple and workable for any kind of stator slot shape for rotor loss analysis.

• Tribology and Lubricants
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• 제16권2호
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• pp.91-98
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• 2000

A slot restrictor air journal bearing has high load capacity and high stiffness. The stability characteristics of the slot restrictor air journal bearing are studied theoretically and experimentally to forecast and to prevent the whirl instability. As for the high speed rotating machinery, the instability called'whirl'occurs when the rotor rotates at a speed more than twice the resonant speed. Once the whirl occurs, rubbing contact between the journal and the bearing occurs mostly and the bearing-rotor system is destroyed ultimately. Therefore, the forecasting and prevention of the occurrence of whirl instability is a very important subject especially to develop highly efficient high speed rotating machinery. The bearing with the slot restrictor that varies about circumferential direction is used for the purpose of the prevention of whirl instability.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제28회 추계학술대회
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• pp.350-357
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• 1998

Slot restrictor air journal bearing has high load capacitance and high stiffness. Stability characteristics of slot restrictor air journal bearing are studied theoretically to forecast and to prevent the whirl instability. As for the high speed rotating machinery, the instability called 'whirl' occurs when the rotor rotates at a speed more than twice the resonant speed. Once the whirl occurs, rubbing contact between the journal and the bearing occurs mostly and the bearing-rotor system is destroyed ultimately. Therefore, the forecasting and prevention of the occurence of whirl instability is a very important subject especially to develop highly efficient high speed machinery. The bearing with the slot restrictor that varies about circumferencial direction is used for the purpose of the prevention of whirl instability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.299-301
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• 1998

The torque characteristic of an induction motor is affected greatly by the slot shape at which the conductors of the rotor are located. In this paper, the three analysis model; general type, deep slot type, double squirrel-cage type, of which the slot shapes are different, were analyzed by FEM at no load, at rated load, and at standstill respectively. The flux distribution and air-gap flux density were also obtained. From the above result, it was confirmed that the analysis models of deep slot and double squirrel-cage had more desirable characteristics than those of general squirrel-cage.

• Journal of Electrical Engineering and Technology
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• 제11권1호
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• pp.135-142
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• 2016

Generally, closed slots are adopted to reduce the water friction loss in both the stator and the rotor of water filling submersible motor due to the special environment of operation. One of the obvious differences between the traditional induction motors and water filling submersible motors is that the submersible motors only need relatively smaller starting torque. This paper aims to analyze the slot leakage reactance of water filling submersible motor during starting transient operation. An improved analytical method which considered the magnetic saturation of the slot bridge and the skin effect of rotor bars is proposed. The slot permeance factor which has a direct impact on the slot leakage reactance is calculated. Then finite element models with different stator slot types are constructed and search coils are introduced to measure the slot flux linkage. Moreover, the starting performances of the models with two typical stator slots are compared and the flux leakage characteristics are obtained. Finally, the results obtained by finite element method are very close to the results obtained by analytical method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.131-134
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• 2002

The optimum design technology using combind F.E.M and eauivalent circuit is so fast and accurate that it can be applied to the optimum rotor design of an inverter-fed induction motor in high efficiency motor making industry. The optimum characteristics fer a rotor slot model of a 3 phase inverter-134 nduction motor was previously verified by a time-step F.E.M. In this paper, four verification models with the design variables near the optimum point are designed to chech whether the characteristics of a slot model presented is not less than those of the near models. The outputs of whole models are analyzed in a time-step Finite Element Method and compared in the experimental test. The economical and efficient selecting method of design variables fur the computer simulation and experimental test is presented in order to assure the optimum point.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권11호
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• pp.742-747
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• 1999

On-line diagnosis system has been developed and is now applied the detection of shorted turns in the field winding of large generator. This system consists of data aquisition system and display PC. The data aquisition system detects voltage waveforms from flux probe sensor installed in the stator slot. The display PC shows theshorted-turn situation of generator rotor winding. A shorted-turn diagnosis test wasperformed on five gas turbine generators at the Seoinchon combined cycle power plant. The test was conducted using an new diagnosis system and digital oscilloscope which can identify the pole location, the slot number and the number of shorted turns within each slot. It is confirmed that results of two systems are very same in the field tests.