• Journal of Power Electronics
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• v.18 no.3
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• pp.736-745
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• 2018

This paper presents an extended state observer (ESO) based direct torque control (DTC) for use in induction motor systems to handle the issues of time delays, load torque disturbances and parameter uncertainties. Direct torque control offers an excellent torque response and it does not require a proportion integration (PI) controller in the current loop. However, a PI controller is still adopted in the outer speed loop to generate the torque reference value, which is a slow method. An ESO based compound control scheme is proposed to improve the response rate and accuracy of the torque reference signal, especially when load torque is injected. In addition, the time delay problem is analyzed and compensated for in this paper to reduce torque ripples. The proposed disturbance compensation technique based direct control scheme is shown to have good performance both in the transient and stable states via simulations and experimental results.

• 전기의세계
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• v.27 no.5
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• pp.69-75
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• 1978

3 phase induction motor applied in the method of connecting it directly across the line needs large current when it starts. At that time, leakage magnetic pathes of interior of the motor are severely saturated and leakage reactances are decreased because of saturation. Consequently, increased current and raised powerfactor yield increase of starting torque. The author, noticing those phenomena, derived experimentally the raion of decreasing leakage reactance from the fact that when voltage applied to motor is increased under locked condition the magnitude of current and phase angle are varied, and determined tha equations of starting current and starting torque, considering the decrease of leakage reactance by the large starting current. The author calculated the characteristics of Current-Time and Speed-Time with the determined equation at specific load conditions, and compared the values obtained from above calculations with those from circle diagram's method and the practically recorded values at same load conditions. Therefore, the authos got a confidience that the results of the derived theory coincide with the practically measured values more well than circle diagram's results and circle diagram's equation should be modified in order to analize the starting status of a induction motor.

• Proceedings of the Korean Society of Embryo Transfer Conference
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• 2002.11a
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• pp.91-91
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• 2002

Considerable attention has been focused on the cryopreservation of semen and estrus induction in dog, as consequence of poor productivity caused by long anestrus period, in order to enhance the productivity of youngs and to preserve the breeds. The objectives of this study were to develop a treatment protocol for estrus induction. Fifty infertilie dogs (age 2∼3 years) were selected for the study and divided into three different estrus induction treatment groups. Group 1: dogs (n=15) were given clomifane (0.1 mg/kg) orally for five days at 12 hr intervals. Group 2: dogs (n=15) were given bromocriptine (50 $\mu\textrm{g}$/kg) orally for five days at 12 hr intervals, followed by single injection intravenously of 500 IU GnRH (Group 3, n=20) when pro-estrus occurred. After being treated, the dogs were evaluated for the rates of estrus induction and time interval lapses from treatment to beginning of the pro-estrus. The estrus induction rates were significantly (P<0.05) higher in both group 2 (9/15, 73.3%) and group 3 (16/20, 80.0%) than that of group 1 (9/15, 60.0%), but did not differ in the groups 2 and 3. No differences were observed in the time interval lapses from treatment to beginning of the pro-estrus in group 2 (7.7 ${\pm}$ 1.2 days) and group 3 (6.9 ${\pm}$ 2.0 days), but significantly (P<0.05) shorter than that of group 1 (9.5 ${\pm}$ 2.1 days). In conclusion, the estrus induction rate of dogs treated with a combination of GnRH and bromocriptine was more effective than use of clomifene or bromocriptine only.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.319-322
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• 1997

In vector control technique, stator currents of an induction motor are transformed to equivalent d-q currents in reference frame consist of d and q axis, each of which is coincide with flux and torque direction respectively. In this paper, the new algorithm is suggested where the stator current through an induction motor torque is monitored by using a vector control method where an additional equipment is not need. The G-programming is used to apply the suggested algorithm in the experiment and this is applied to an actual system to monitor the torque value of an induction motor on real time. To solve the vibration trouble of estimated torque caused from an unbalanced real rotating speed of an induction motor and measured rotating speed by suggesting the reconstructed in a method based on measurement current signal. This produced system testifies an accuracy of an induction motor through the experiment by comparing the reference value of the control method.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.312-316
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• 2005

The single phase induction motor has been commonly applied to small-sized electrical appliances because of its low cost, but it has low efficiency and large torque ripple, and it is incapable of speed control. However, two-phase induction motors have small torque ripple, high efficiency and variable speed control, because they are inverter fed. In this paper, the dynamic characteristics of the two-phase induction motor, such as the torque ripple, current and speed, are analyzed by using the time-stepping finite element method, and compared with the cage-type single phase induction motor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.771-775
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• 2011

This paper presents design process of linear induction motor in dynamic tester for catenary-current collection. To minimize length of rail for dynamic tester for catenary-current collection, accelerating performance of the linear induction motor is very important. So the design process of linear induction motor considered in this paper is different with general design process of linear induction motor, because dynamic tester has three type driving region, as accelerating region, constant speed region, and braking region. Considering accelerating performance of motor, distance and time from starting point to constant speed region were concerned for load condition of motor. Designed linear induction motor was analyzed by 2-dimensional finite element method. Using mechanical dynamics simulation with analysis result of 2-dimensional finite element method and accelerating performance of designed motor was proved.

• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.454-460
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• 2005

The goal of this research was to better understand the mechanism of environmental control of PEPC expression from Hydrilla verticillata grown under $CO_2$ stress. When PEPC concentration was plotted against $CO_2$ compensation point (${\Gamma}$), a linear increase in PEPC concentration was seen with a decrease in $CO_2$ compensation point. ${\Gamma}$ was measured on each day of the time course induction. Hydrilla plants exhibited an initially large decrease in ${\Gamma}$ between day 0 and day 1; thereafter, the ${\Gamma}$ declined in a fairly linear trend for the remaining 5 day time course. PEPC activity varied greatly over the time course. PEPC activity increased daily from day 0 through day 5 of the time course. Activity of PEPC increased almost 4-fold over the time course induction. The two upper bands with the approximately 100 kD mass are the PEPC subunits and PEPC was barely detectable in day 0 but increased through day 4 with day 5 being approximately equal to day 4. We provide evidence of increased PEPC protein concentration, and increased PEPC enzyme activity in as little as 24 h after beginning of induction.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2139-2142
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• 1997

The most important thing in vector control scheme is the knowledge of accurate electrical motor parameters. These parameters can computed by conventional motor test, such as no-load and locked rotor tests. However, the values from these tests are different from actual motor parameters, and the adjustment process of the parameters is time consuming. This paper presents an auto-tuning method for vector control of induction motor. The tuning algorithm is based on the rotor flux behavior of the induction motor for stepwise torque current command. The transient terminal voltage caused by the undesirable variation of the rotor flux is used for tuning the slip gain $K_5$ defined as the inverse of the rotor time constant. The electrical parameters of induction motor can also calculated by this method. The presented method is evaluated through the computer simulations.

• Journal of Power System Engineering
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• v.5 no.3
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• pp.95-103
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• 2001

This study is applied to common induction motor, and vector control is realized by using an indirect type of induction motor which has a simple composition. In this study extended Kalman filter is used from control theoretical viewpoint, and primary resistance and secondary resistance which change according to the temperature of motor are simultaneously estimated. This paper aims to research an indirect vector control in which the secondary resistance obtained from this estimation is consistent with secondary flux. This estimation is made by on-line estimation, but on-line estimation is difficult because extended Kalman filter takes long time in computation time. So off-line estimation was made on the assumption that the variation of temperature in motor is slow temporally.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.695-698
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• 2002

Induction heating process is one of the most efficient heating process in terms of temperature control accuracy and heating time saving. In the past study, fabrication process of cellular 6061 alloys by powder metallurgical route and induction heating process was studied. To supplement the framing conditions that studied in past study, effect of induction heating capacity and holding time at foaming temperature were investigated. Under the achieved framing conditions, teamed 6061 alloys were fabricated for variation of foaming temperature, and porosities(%)-foaming temperature curves were obtained by try-error experimental method. Uniaxial compression tests were performed to investigate the relationship between porosities(%) and stress-strain curves of framed 6061 alloy. Also, energy absorption capacity and efficiency were calculated from stress-strain curves to investigated. Moreover, dependence of plateau stress on strain rate was investigated in case of cellular 6061 alloy with low porosities(%)