• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1066-1071
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• 2005

This paper presents the two lossless auxiliary inductors-assisted voltage source type half bridge (single ended push pull: SEPP) series resonant high frequency inverter for induction heated fixing roller in copy and printing machines. The simple high-frequency inverter treated here can completely achieve stable zero current soft switching (ZCS) commutation for wide its output power regulation ranges and load variations under its constant high frequency pulse density modulation (PDM) scheme. Its transient and steady state operating principle is originally described and discussed for a constant high-frequency PDM control strategy under a stable ZCS operation commutation, together with its output effective power regulation characteristics-based on the high frequency PDM strategy. The experimental operating performances of this voltage source SEPP ZCS-PDM series resonant high frequency inverter using IGBTs are illustrated as compared with computer simulation results and experimental ones. Its power losses analysis and actual efficiency are evaluated and discussed on the basis of simulation and experimental results. The feasible effectiveness of this high frequency inverter appliance implemented here is proved from the practical point of view.

• Journal of Power Electronics
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• v.13 no.3
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• pp.369-380
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• 2013

Direct torque control based on space vector modulation (SVM-DTC) protects the DTC transient merits. Furthermore, it creates better quality steady-state performance in a wide speed range. The modified method of DTC using SVM improves the electrical magnitudes of asynchronous machines, such as minimizing the stator current distortions, the stator flux with electromagnetic torque without ripple, the fast response of the rotor speed, and the constant switching frequency. In this paper, the proposed method is based on two new control strategies for direct torque control with space vector modulation. First, fuzzy logic control is used instead of the PI torque and a PI flux controller to minimizing the torque error and to achieve a constant switching frequency. The voltages in the direct and quadratic reference frame ($V_d$, $V_q$) are achieved by fuzzy logic control. In this scheme, the switching capability of the inverter is fully utilized, which improves the system performance. Second, the close loop of stator flux estimation based on the voltage model and a low pass filter is used to counteract the drawbacks in the open loop of the stator flux such as the problems saturation and dc drift. The response of this new control strategy is compared with DTC-SVM. The experimental and simulation results demonstrate that the proposed control topology outperforms the conventional DTC-SVM in terms of system robustness and eliminating the bad outcome of dc-offset.

• Journal of Ship and Ocean Technology
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• v.6 no.4
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• pp.1-12
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• 2002

A control system for an automated line heating process is developed by use of object-oriented methodology. The main function of the control system is to provide real-time heating information to technicians or automated machines. The information includes heating location, torch speed, heating order, and others. The system development is achieved by following the five steps in the object-oriented procedure. First, requirements are specified and corresponding objects are determined. Then, the analysis, design, and implementation of the proposed system are sequentially carried out. The system consists of six subsystems, or modules. These are (1) the inference module with an artificial neural network algorithm, (2) the analysis module with the Finite Element Method and kinematics analysis, (3) the data access module to store and retrieve the forming information, (4) the communication module, (5) the display module, and (6) the measurement module. The system is useful, irrespective of the heating sources, i.e. flame/gas, laser, or high frequency induction heating. A newly developed automated line heating machine is connected to the proposed system. Experiments and discussions follow.

• Proceedings of the KIEE Conference
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• 1999.11a
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• pp.1-3
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• 1999

EM (ElectroMagnetic) pump is used for the purpose of transporting liquid sodium coolant with electrical conductivity in the LMR(Liquid Metal Reactor). (In the present study, pilot EM pump has been designed by using of equivalent circuit method which is commonly employed to analyze linear induction machines for the test of removal of residual heat. The length and diameter of the pump have fixed values of 840 mm and 101.6 mm each by taking account of geometrical size of circulation loop for the installation of EM pump. Flowrate versus developing pressure is related from Laithwaite's standard design formula and the characteristic analyses of developing force and efficiency are carried out according to change of input frequency. From the characteristic curve, input frequency of 13 Hz is determined as the design frequency. On the other hand, The annular air gap size of 6.05 mm is selected not to bring about too much hydraulic loss. Resultantly design analysis makes pump have the electrical input of 604 VA and the hydrodynamical capacity of 1.3 bars and 40 l/min.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.10
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• pp.895-900
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• 2007

Partial discharge(PD) test can be performed either when the rotating machine is not operating(off-line) or during normal machine operation(on-line). This paper presents an on-line and off-line PD test on a large hydro-generator and induction motor using the same PD acquisition system(PDAS) and ceramic coupler(CC) sensor. PD signal characteristics of CC sensor proved similar with that of epoxy mica coupler(EMC) sensor as a results of PD test for simulated defect winding and frequency response test. A comparison of on-line and off-line PD test for PD characteristic parameters-phase resolved PD(PRPD), maximum PD value(Qmax) and PD occurrence energy(POE)-indicated that on-line PD test could reliably and effectively diagnose insulation conditions which were verified by off-line PD test.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.147-149
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• 1994

In designing high efficiency electrical machines, calculation of iron loss is very important. And it is reported that in the induction motor and in the T-joint of 3 phase transformer, there occurred rotational magnetic field and much iron loss is generated owing to this field. In this paper, rotational power loss in the electrical machine under rotational magnetic field is discussed. Until now, loss analysis is based on the magnetic properties under alternating field. And with this one dimensional magnetic propertis, it is difficult to express iron loss under rotational field. In this paper, we used two dimensional magnetic property data for the numerical calculation of rotational power loss. We used finite element method for calculation and the analysis model is two dimensional magnetic property measurement system. We used permeability tensor instead of scalar permeability to present two dimensional magnetic properties. And in this case, we cannot uniquely define energy functional because of the asymmetry of the permeability tensor, so Galerkin method is used for finite element analysis.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.13-15
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• 1998

EM(Electro Magnetic) pump is used for the purpose of transporting liquid sodium coolant with electrical conductivity in the LMR(Liquid Metal Reactor). In the present study. pilot EM pump has been designed by using of equivalent circuit method which is commonly employed to analyze linear induction machines for the test of removal of residual heat. The length and diameter of the pump have fixed values of 840 mm and 101.6 mm each by taking account of geometrical size of circulation loop for the installation of EM pump. Flowrate versus developing pressure is related from Laithwaite's standard design formula and the characteristic analyses of developing force and efficiency are carried out according to change of input frequency. From the characteristic curve, input frequency of 13 Hz is determined as the design frequency. On the other hand, The annular air gap size of 6.05 mm is selected not to bring about too much hydraulic loss. Resultantly design analysis makes pump have the electrical input of 604 VA and the hydrodynamical capacity of 1.3 bars and 40 l/min.

• Journal of the Korea Society of Computer and Information
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• v.18 no.7
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• pp.23-35
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• 2013

This paper proposes an effective technique that is used to automatically extract feature vectors from vibration signals for fault classification systems. Conventional mel-frequency cepstral coefficients (MFCCs) are sensitive to noise of vibration signals, degrading classification accuracy. To solve this problem, this paper proposes spectral envelope cepstral coefficients (SECC) analysis, where a 4-step filter bank based on spectral envelopes of vibration signals is used: (1) a linear predictive coding (LPC) algorithm is used to specify spectral envelopes of all faulty vibration signals, (2) all envelopes are averaged to get general spectral shape, (3) a gradient descent method is used to find extremes of the average envelope and its frequencies, (4) a non-overlapped filter is used to have centers calculated from distances between valley frequencies of the envelope. This 4-step filter bank is then used in cepstral coefficients computation to extract feature vectors. Finally, a multi-layer support vector machine (MLSVM) with various sigma values uses these special parameters to identify faulty types of induction motors. Experimental results indicate that the proposed extraction method outperforms other feature extraction algorithms, yielding more than about 99.65% of classification accuracy.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.5
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• pp.71-85
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• 1993

The Cycloconverter that the author is going to treat in this paper, has strong advantages over the D.C. Link Inverter in points of chattering torque problem and natural commutation. Thus, the Cycloconverter is expected to be well applied to large and low-speed machines which require better speed control at low frequency. But the control circuit of Cycloconverter has two weak points described as follows. 1) Because of its rather complicated control circuit, it is likely to be illoperating due to unexpected noise signals, thus the higher the accuracy and reliability of the circuit is required to be, the more the circuit may cost. 2) Because the load current is not purely sinusoidal, the Cycloconverter may possibly be destroyed in case of inaccurate convert switching resulted from the difficulties in detecting the load current-zero and the current direction at the moment. In this paper, the author first of all intends to design and build a modified VVVF-type Noncirculating Current Cycloconverter to which recently proposed control methods are applied for improving the circuit simplicity, the control performance, and the system reliability. And then, experiments for observing the output waveforms of the Cycloconverter which is controlled by Singled-Board Computer using 8086 16-bit microprocesser are carried out. Finally the author concludes the result of this study as follows. 1) By replacing the conventional analog control circuits such as Reference Wave Generator, Cosine Timing Wave Generator, and Comparator with softwares, a great circuit simplicity is achieved. 2) The output of the designed Cycloconverter changes its frequency very fast without showing discontinuity of its waveform, and this waveform characteristics enables the smooth speed control of Induction Motor. 3) The design control circuit of Cycloconverter can be applied to the systems of 12 or 24 pulses because of its short processing period.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.60 no.1
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• pp.71-79
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• 2024

In compliance with environmental regulations at sea and the introduction of unmanned autonomous ships, electric propulsion ships are garnering significant attention. Induction machines used as propulsion electric motor (PEM) have maintenance advantages, but speed control is very complicated and difficult. One of the most commonly used techniques for speed control is DTC (direct torque control). DTC is simple in the reference frame transformation and the stator flux calculation. Meanwhile, two-level and three-level voltage source inverters (VSI) are predominantly used. The three-level VSI has more flexibility in voltage space vector selection compared to the two-level VSI. In this paper, speed is controlled using the DTC method based on the specifications of the PEM. The speed controller employs a PI controller with anti-windup functionality. In addition, the characteristics of the two-level VSI and three-level VSI are compared under identical conditions. It was confirmed through simulation that proper control of speed and torque has been achieved. In particular, the torque ripple was small and control was possible with a low DC voltage at low speed in the three-level VSI. The study confirmed that the application of DTC, using a three-level VSI, contributes to enhancing the system's response performance.