• Title/Summary/Keyword: Induction Time

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Crystallization Characteristics of Metallocene Low Density Polyethylene/Low Density Polyethylene Blends (메탈로센 선형 저밀도 폴리에틸렌/선형 저밀도 폴리에틸렌 블렌드의 결정화 거동)

  • 김경룡;한정우;강호종
    • Polymer(Korea)
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    • v.25 no.6
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    • pp.840-847
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    • 2001
  • The crystallization characteristics of metallocene linear low density polyethylene (m-LLDPE)/linear low density polyethylene (LLDPE) blends were investigated. The effect of blending on the induction time for crystallization, spherulites growth rate, and maximum size of spherulites was mainly considered in this study. The formation of separate crystal which is well known crystallization behavior in LLDPE/LDPE blend was not found in m-LLDPE/LLDPE blends. The blending m-LLDPE to LLDPE caused the dramatic decrease in the induction time of m-LLDPE/LLDPE blends but it seems that the blend composition shows less effect on the induction time. Lower branching number in m-LLDPE resulted in the increasing of spherulites growth rate and the maximum size of spherulites is depend upon both the induction time and spherulites growth rate of LLDPE component affected by m-LLDPE.

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Compensation of the rotor time constant of induction motor using current error feedback (전류오차 궤환을 이용한 유도전동기 회전자 시정수 보상)

  • 김승민;이무영;권우현
    • 제어로봇시스템학회:학술대회논문집
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    • 1997.10a
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    • pp.195-198
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    • 1997
  • This paper proposes the effective compensation method of the rotor time constant of induction motor. An indirect vector control method is highly dependent on the motor parameters. To solve the problem of performance degradation due to parameter variation in an indirect vector control of induction motor, we compensate the rotor time constant by current error feedback. The proposed method is a simple on-line rotor time constant compensation method using the information from terminal voltages and currents. As the current error, difference between current command and estimated current, approaches to zero, the value of rotor time constant in an indirect vector controller follows the real value of induction motor. This scheme is valid transient region as well as steady state region regardless of low or high speed. This method is verified by computer simulation. For this, we constructed the simulation model of induction motor, indirect vector controller and current regulated PWM (CRPWM) voltage source inverter (VSI) using SIMULINK in MATLAB.

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Reheating of Semi-Solid Material Using Multi-Capacity Induction Heating System (다출력 유도 가열 시스템에 의한 반용융 소재의 재가열)

  • 정홍규
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1999.03b
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    • pp.199-202
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    • 1999
  • Many processing times for fabricating complex shaped parts by near net shape process such as thixoforming or semi-solid forming, are required due to the time for die design, induction heating and forming process. Therefore, for the thixoforming process, multi-capacity induction heating process is very important due to the reduction of the processing time and cost. It is indispensable to adopt a power-time heating pattern which manages to conciliate complete eutectic melting at the core with limited overheating at the periphery. The total reheating time is thus dependent on billet diameter; in inches$(pm20%)$. Typically, high frequency is used for the rapid reheating of the billet to the eutectic temperature range and low frequency for the remelting of the desired fraction of liquid and for the radial homogeneization of the liquid fraction. So in this study, the multi-capacity induction heating conditions of ALTHIX 86s alloy to reduce the processing time and cost would be proposed. The suitability of multi-capacity induction heating conditions would be verified through the comparison to Garat's data.

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A Process for the Control of Cell Size of 6061 Al foams by Multi-step Induction Heating Method (다출력 유도가열 공정을 이용한 다공질 6061 알루미늄 합금의 기공 제어 공정)

  • 윤성원;강충길
    • Transactions of Materials Processing
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    • v.12 no.5
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    • pp.449-456
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    • 2003
  • Multi-step induction heating process was applied to the powder compact melting technique as a new heating process to achieve pinpoint accuracy, faster cycle time, repeatability, non-contact and energy-efficient heat in a minimal amount of time. The objective of this study is the establishment of the input data diagram of multi step induction heating process for automation of the fabrication process of 6061 Al foams with desired density. At first, proper induction coil was designed to obtain a uniform temperature distribution over the entire cross sectional area of specimen. By using this coil, foaming experiments were performed to investigate the multi-step induction heating conditions such as capacity, temperature and time conditions of each heating and holding step. On the basis of the obtained multi-step induction heating conditions, relationship between final heating temperature and fraction of porosity was investigated.

Steady-State Current Characteristics for Squirrel Cage Induction Motor according to Design Variables of Rotor Bars using Time Difference Finite Element Analysis

  • Kim, Young Sun
    • Journal of Magnetics
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    • v.22 no.1
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    • pp.104-108
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    • 2017
  • Induction motors have wide applicability in many fields, both in industrial sectors and households, for their advantages of a high efficiency and robust structure. The introduction of power-source-containing harmonics into the induction motor winding lowers its efficiency and increases its temperature, greatly affecting its operation characteristics. In this study, we performed an electromagnetic field analysis using the time-difference finite-element method with the purpose of analyzing the steady-state current characteristics of an induction motor. Additionally, we calculated the steady-state current with a method combining an electromagnetic field equation and a circuit equation. In the electromagnetic field analysis, the nonlinearity was taken into account using the Newton-Raphson method, and a backward time-difference method was employed for the time derivative term. Then, we compared the steady-state current of the induction motor obtained by calculation with the experimentally measured values, thus validating the proposed algorithm. Furthermore, we analyzed the impacts of the shape and material of the rotor conductor bar of the induction motor on the steady-state current of the main winding.

A Study on Time Optimal Position Control of A CSI Fed Induction Motor (전류형 인버터에 의해 구동되는 유도전동기의 시간최적 위치제어에 관한 연구)

  • 박민호;원충연
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.36 no.8
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    • pp.529-538
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    • 1987
  • The time optimal position control scheme based on the Pontryagin's minimum principle is proposed in the current source inverter(CSI) fed induction motor system. The field oriented induction motor system is modelled with a second order plant and a switching curve is obtained by solving Hamiltonian equation. The validity of time optimal control solution has been verified by experimental tests carried out with a prototype MC68000 based microcomputer system, and 5Hp induction motor. Experimental results are in a close agreement with those the digital simulation ones.

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Development of an Induction Motor Vector Control System Using Simulink/RTW (Simulink/RTW를 이용한 유도전동기 벡터제어시스템 개발)

  • 강문호
    • 제어로봇시스템학회:학술대회논문집
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    • 2000.10a
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    • pp.119-119
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    • 2000
  • In this research an induction motor vector control system was developed using Simulink and RTW(Real Time Workshop). On the Simulink window, control system is designed in the form of block diagrams, program codes are produced automatically with the RTW, then c compiler compiles the program codes. With this automatic real time program producing mechanism rapid prototyping is realized without the time-consuming manual program coding procedures. To show effectiveness of the proposed designing scheme a DSP-based induction motor vector control system was constructed and implemented

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The Pessimistic Induction and Space-Time Theories (비관적 귀납과 시공간 이론)

  • Yang, Kyoung-Eun
    • Korean Journal of Logic
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    • v.14 no.3
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    • pp.1-26
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    • 2011
  • This essay attempts to evaluate the pessimistic induction within the case of the historical development of space-time theories, which are claimed to undergo a radical ontological change providing evidence for the pessimistic induction. In my view, this claim misleads us to see the discontinuity of the structure of classical and relativistic space-time by means of a doubtful interpretation of space-time theories, which holds that space-time causally explains the phenomena of motions.

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Time Delay Compensation for Output Voltage Vector Selection in Direct Torque Control of Induction Machine (유도전동기의 직접토크제어 시스템에서 출력전압벡터선정을 위한 시간지연의 보상)

  • 최병태;박철우;권우현
    • Journal of Institute of Control, Robotics and Systems
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    • v.9 no.8
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    • pp.632-639
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    • 2003
  • This paper proposes a simple compensation scheme for the time delay caused by measurement, calculation and selection of voltage vector in Direct Torque Control (DTC) of an induction motor. In general scheme, it is difficult to know the exact delay time, furthermore the delay time can be varied by program routines for calculation and processing of measured data. In this proposed scheme, by applying voltage vector at the beginning of next sampling period, a fixed delay time is achieved and its compensation becomes much simpler. Furthermore, with the simple compensation algorithm, an improved performance can be achieved by shortening sampling period. Experimental results prove the feasibility of the proposed scheme in induction motor control.

Sensorless Speed Control of Induction Motor Using Observation Technique (관측기관을 이용한 유도전동기의 센서리스 속도제어)

  • 이충환
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.1
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    • pp.96-102
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    • 1999
  • Sensorless speed estimation in induction motor systems is one of the most control engineers. Based on the estimated speed the vector control has been applied to the high precision torque control however most speed estimation methods use adaptive scheme so that it takes long time to estimate the speed. Thus the adaptive estimation scheme is not effective to the induction motor which requires short sampling time. In this paper a new linearized equation of induction motor system is proposed and a sensorless speed estimation algorithm based on observation techniques is developed. First the nonlinear induction motor equation is linearized at an equilibrium point. Second a proportional integral(PI) observer is applied to estimate the speed state in the induction motor system. Finally simulation results will assure the effectiveness of the new linearized equation and the sensorless estimation algorithm by using PI observer in the nonlinear induction motor system.

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