• Title/Summary/Keyword: Primary frequency control

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A Study of the Current-Diagram Method for Calculating Induction Motor Characteristics with Adjustable Frequency (가변주파수에 있어서 유도잔동기특성의 도식산정법에 관한 연구 제3보)

  • Min Ho Park
    • 전기의세계
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    • v.18 no.5
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    • pp.20-25
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    • 1969
  • The development of the frequency convertors using semiconductors devices makes it possible to control the speed of A.C. motors easily. It is now economically feasible to provide them with power at adjustable frequency using silicon-controlled rectifier (or thyristor) inverters. In such a case, in order to operate an induction motor efficiently over a wide speed range, it must be supplied from a variable frequency source of which frequency is adjustable over the speed range of the motor. It is desired to observe the changes in characteristics as primary current, torque-speed of induction motor etc. at any optional frequency. Although the characteristics can be obtained by means of the conventional methods, they require very complicated precedures of calculations. The Current Diagram Method in this paper suggests a new approach to simpler calculations of the characteristics, using the motor constants at reference frequency. The conclusions of this study are summarized as follows: 1) The equations of stator current at adjusted frequency were derived to construct graphical chart and the current circle required for the Current Diagram Method. 2) The radius, center of the current circle and the vector locus, the basis for calculating the characteristics, at any desired frequency could be easily determined with the aid of both the derived graphical chart and current circle at reference frequency. 3) The method was shown to be applicable to the various types of 3-phase induction motors and also dealt with its application to the split-phase, condenser motors.

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A Study on Off-Gas Treatment of an Air Stripping Tower Using a Plasma Reactor

  • Lim, Gye-Gyu;Yoo, Ho-Sik
    • Journal of Korean Society for Atmospheric Environment
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    • v.9 no.E
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    • pp.382-389
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    • 1993
  • An evaluation of a plasma reactor was conducted to investigate its potential as a feasible and economical off-gas control technology for an air stripping tower (AST). The plasma reactor was powered by an alternating current with frequencies up to 1000Hz. The study showed that over 90% conversion of gas-phase trichloroethylene (TCE) can be achieved. An optimum frequency for the laternating current existed for maximum power input. The optimum frequency was dependent on the reactor geometry and the primary voltage applied. for a fixed geometry, a plasma reactor has a limited capacity for flow rate. Even though it is a feasible process to control off-gases, further investigations should be conducted to develop a more economic process.

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Single Phase-Shift Modulation with Variable-Frequency to Reduce Conduction Losses of DAB Converters (DAB 컨버터의 전도 손실 저감을 위한 가변 주파수의 단일 위상 시프트 변조기법)

  • Dao, Ngoc Dat;Lee, Dong-Choon
    • Proceedings of the KIPE Conference
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    • 2019.11a
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    • pp.124-125
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    • 2019
  • This paper proposes a novel control method to minimize conduction losses of dual active bridge (DAB) converters for on-board chargers of electric vehicles (EVs). In the control method, two variables are regulated, which are the phase-shift angle between the primary and secondary full bridges and the switching frequency. From time-domain analysis, an optimal phase-shift angle is derived to achieve the minimum RMS value of the transformer current. The proposed method was implemented for a 3.6-kW SiC-based prototype to validate its effectiveness. A high efficiency over 97.3% has been achieved for a wide output voltage range.

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A Study on the Current-diagram Method for Calculating Induction Motor Characteristics with Adjustable Frequency (가변주파수에 있어서 유도전동기의 특성도식 산정법에 관해서 제1보)

  • Min-Ho Park
    • 전기의세계
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    • v.17 no.3
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    • pp.29-38
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    • 1968
  • The development of the frequency converter using semiconductor enables to easily control the speed of A.C. motors. It is now technically possible and economically feasible to provide them with power at variable frequency, using silicon-controlled-rectifier (or thyristor) inverters. In such a case, if an induction motor is to be operated efficiently over a wide speed range, it must be supplied from a variable-frequency source whose frequency is adjustable over a range similar to that required for the motor speed. It is desired to observe how several characteristics are changed such as primary current, torque-speed, etc. Although the characteristics could be obtained by means of the conventional method, it requires very complicated calculation. It is assumed that the charateristics above are easily investigated by means of current diagram method from variable circuit constants relating to the motor which is designed in rated frequency. In this paper, the results of the study on the current-diagram method and its application are described as follows; (1) In order to discuss the construction of current diagram, the equation of the stator current with adjustable frequency was derived for applying the Current Diagram Method. (2) The radius, the center of the current circle and current vector locus at any desired frequency could be easily determined with the aid of both above mentioned equation and the standard current diagram at reference frequency. (3) This method could be applicable to the various types of Induction Motors, and this paper has dealt with its application to the capacitor, split-phase and 2-phase types of motors.

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Control of Combustion Instabilities in a Gas Turbine Combustors Through Secondary Fuel Injection (가스터빈 연소기내 2차연료분사에 의한 연소 불안정성의 제어)

  • Jeon, C.H.;Santavicca, Domenic A.
    • Journal of the Korean Society of Combustion
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    • v.3 no.1
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    • pp.59-69
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    • 1998
  • The results of study on the active control of naturally occurring combustion oscillations with a single dominant frequency in an atmospheric dump combustor are presented. Control was achieved by an oscillatory infection of secondary fuel at the dump plane. A high speed solenoid valve with a maximum frequency of 250Hz was used as the actuator and a sound level meter, located at the combustor exit, measured the pressure fluctuations which served as the feedback signal for the control loop. Instability characteristics were mapped over a range of mean mixing section velocities from 6.7 m/s-9.3 m/s and with three mixing conditions. Different fuel/air mixing conditions were investigated by introducing varying percentages of primary fuel at two locations, one at the entrance to the mixing section and one 6 mixing tube diameters upstream of the dump plane. Control studies were conducted at a mean velocity of 9.3 m/s, with an air temperature of $415^{\circ}C$, and from flame blowout to the stoichiometric condition.

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A Study Of The Current-Diagram Method For Calculating Induction Motor Characteristics With Adjustable Frequency (가변주파수에 있어서 유도전동기특성의 도시산정법에 관한 연구)

  • Min Ho Park
    • 전기의세계
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    • v.18 no.4
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    • pp.22-30
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    • 1969
  • The development of the frequency convertors using semiconductors devices makes it possible to control the speed of A.C. motors easily. It is now economically feasible to provide them with power at adjustble frequency using silicon-controlled rectifier (or thyristor) inverters. In such a case, in order to operate an induction motor efficiently over a wide speed range, it must be supplied from a variable frecuency source of which frequency is adjustable over the speep range of the motor. It is desired to observe the changes in characteristics as primary current, torque-speed of induction moter etc. at any optional frequncy. Although the charactheristies can be obtained by means of the conventional methods they require very complicated precedures of calcuations. The Current Diagram Method in this paper suggests a new approach to simpler calcuations of the characteristics, using the motor constants at reference frequency. The conclusions of this study are summarized as follows: (1) The equations of stator current at adjusted frequency were derived to construct graphical chart and the current circle required for the Current Diagrm Method. (2) The radius, center of the current circle and the vector locus, the basis for calculating the characteristics, at any desired frequency could be easily determined with the aid of both the derived graphical chart and current circle at reference frequency. (3) The method was shown to be applicable to the various types of 3-phase induction motors and also dealt with its application to the split-phase, condenser motors.

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Variable Output and Parallel Operation Control of EV Charger (전기자동차용 충전기의 가변출력 및 병렬운전 제어)

  • Lee, Sang-Hyeok;Kang, Seong-Gu;Awasthi, Prakash;Hwang, Jung-Goo;Lee, Seung-Yul;Wi, Han-Byul;Park, Sung-Jun
    • The Transactions of the Korean Institute of Power Electronics
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    • v.18 no.2
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    • pp.153-160
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    • 2013
  • This research paper describes the development of battery charger with a variable output voltage capacity for charging the batteries used in electrical vehicles. The voltage and current accordingly is control via the buck converter that receives three phase current at primary side and fed to bridge rectifier which is comprised of full bridge converter and HFTR(High Frequency Transformer) for isolation and a square wave AC output. The transformer primary side is in series to divide certain charging current and the secondary side is comprised of six fix transformers so that they can generate certain amount of power and various output voltage through relay connection using 6 DC outputs. Moreover, all parallel connected full bridge serial resonant converter communicate together with upper(main) controller. The constructed structure is verified by conducting the test on PSIM as well as experimentally.

Salt Processed Food and Gastric Cancer in a Chinese Population

  • Lin, Si-Hao;Li, Yuan-Hang;Leung, Kayee;Huang, Cheng-Yu;Wang, Xiao-Rong
    • Asian Pacific Journal of Cancer Prevention
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    • v.15 no.13
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    • pp.5293-5298
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    • 2014
  • To investigate the association between salt processed food and gastric cancer, a hospital based case-control study was conducted in a high risk area of China. One hundred and seven newly diagnosed cases with histological confirmation of gastric cancer and 209 controls were recruited. Information on dietary intake was collected with a validated food frequency questionnaire. Unconditional logistic regression was applied to estimate the odds ratios with adjustment for other potential confounders. Comparing the high intake group with never consumption of salt processed foods, salted meat, pickled vegetables and preserved vegetables were significantly associated with increased risk of gastric cancer. Meanwhile, salt taste preference in diet showed a dose-response relationship with gastric cancer. Our results suggest that consumption of salted meat, pickled and preserved vegetables, are positively associated with gastric cancer. Reduction of salt and salt processed food in diets might be one practical measure to preventing gastric cancer.

Analysis of Voltage Stress in Stator Windings of IGBT PWM Inverter-Fed Induction Motor Systems

  • Hwang Don-Ha;Lee Ki-Chang;Jeon Jeong-Woo;Kim Yong-Joo;Lee In-Woo;Kim Dong-Hee
    • KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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    • v.5B no.1
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    • pp.43-49
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    • 2005
  • The high rate of voltage rise (dv/dt) in motor terminals caused by high-frequency switching and impedance mismatches between inverter and motor are known as the primary causes of irregular voltage distributions and insulation breakdowns on stator windings in IGBT PWM inverter-driven induction motors. In this paper, voltage distributions in the stator windings of an induction motor driven by an IGBT PWM inverter are studied. To analyze the irregular voltages of stator windings, high frequency parameters are derived from the finite element (FE) analysis of stator slots. An equivalent circuit composed of distributed capacitances, inductance, and resistance is derived from these parameters. This equivalent circuit is then used for simulation in order to predict the voltage distributions among the turns and coils. The effects of various rising times in motor terminal voltages and cable lengths on the stator voltage distribution are also presented. For a comparison with simulations, an induction motor with taps in the stator turns was made and driven by a variable-rising time switching surge generator. The test results are shown.

Robust controller design for the rotational maneuver of a flexible arm (유연한 arm의 1축 회전 기동을 위한 강인성 제어기 설계)

  • 방효충;박영웅;남문경;황보한
    • 제어로봇시스템학회:학술대회논문집
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    • 1997.10a
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    • pp.1322-1325
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    • 1997
  • A new feedback control law design techniqed usign of-off thrusters for the rotational maneuver of a flexible arm is discussed in this study. a two state on-off thruster actuator is taken as a primary actuation device for theis study. The on-off thruster operation is emulated in conjunction with the conventioal minimum-time trackig control law. The actuator input region is divided into two separate parts ; one is constant input and the other is time varying tegion. the new control law has potential applicatioin for the relatively low frequency structure such as large flexible space structure being currently used in various space echnology areas.

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