• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.49 no.1
• /
• pp.54-61
• /
• 2000

Conventionally, ZVS FB DC/DC converter was controlled by monolithic IC UC3879, which includes the functions of oscillator, error amplifier and phase-shift circuit. Also, microprocessor and DSP have been widely used for the remote control and for the immediate waveform control in ZVS FB DC/DC converter. However the conventional microprocessor controller is complex and difficult to control because the controller consists of analog and digital parts. In the case of the control of FB DC/DC converter, the output is required of driving a direct signal to the switch drive circuits by the digital controller. So, this paper presents the method and realization of designing the digital-to-phase shift PWM circuit controlled by DSP (TMX320C32) in a 2,500A, 40㎾ ZVS FB DC/DC converter.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.54 no.4
• /
• pp.201-207
• /
• 2005

This paper has investigated the sensorless vector control method of induction motor based on the stator flux oriented voltage equation and the digital low pass filter (LPF) with compensator of phase/gain. The Proposed vector control method is easy to decide the stator reference voltages and control of motor, since it is based on stator flux vector But this method has sensitive structure to excessive sensor noise and PWM pulsating components of stator currents because the measured stator currents are directly used to compensate the internal resistive voltage drop at the determination of stator reference voltages. To eliminate the noise sensitive of proposed vector drive, this paper propose the digital LPF with compensator of phase/gain base on orthogonal property of stator current vector in stationary $\alpha$, $\beta$ reference frame. The proposed methods have been simulated and implemented on a sensorless vector drive for 750W three-phase induction motor. The simulation and experimental results demonstrate effectiveness of the proposed methods.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.55 no.10
• /
• pp.521-527
• /
• 2006

After various measuring methods and system were investigated, Rogowski colis for the measurement of parameters in current zero region were designed and manufactured. Using the Rogowski coils and a 38kV 40kA VCB (vacuum circuit breaker), at last the post-arc current has been successfully measured firstly. It was found that the Rogowski coils used in this study have good characteristics and propriety to measure the parameters of current zero. We realized that the data processing for evaluating the post-arc current from the experimental results needs much more careful attention than that for building the measuring technique and system. The magnitude of post-arc current and the falling time of it to zero are proportioned to the rate of current di/dt. The magnitude of post-arc currents were around $1{\sim}3A$ to the interruption current of $20{\sim}30kA$ in the model VCB.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.55 no.10
• /
• pp.491-497
• /
• 2006

For high efficiency and easy speed control of brushless DC (BLDC) motor, the demand of BLDC motor is increasing. Especially demand of interior permanent magnet (IPM) BLDC with high efficiency and high power in electric motion vehicle is increasing. However, IPM BLDC basically has a high cogging torque that results from the interaction of permanent magnet magnetomotive force (MMF) harmonics and air-gap permeance harmonics due to slotting. This cogging torque generates vibration and acoustic noises during the driving of motor. Thus reduction of the cogging torque has to be considered in IPM BLDC motor design by analytical methods. This paper proposes the cogging torque reduction method for IPM BLDC motor. For reduction of cogging torque of IPM BLDC motor, this paper describes new technique of the flux barriers design. The proposed method uses sinusoidal form of flux density to reduce the cogging torque. To make the sinusoidal air-gap flux density, flux barriers are applied in the rotor and flux barriers that installed in the rotor produce the sinusoidal form of flux density. Changing the number of flux barrier, the cogging torque is analyzed by finite element method. Also characteristics of designed model by the proposed method are analyzed by finite element method.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.55 no.1
• /
• pp.1-8
• /
• 2006

Now a day, owing to high efficiency and easy speed control of brushless DC(BLDC) motor, the demand of BLDC motor that has high power and low noises are increasing. Especially demand of interior permanent magnet(IPM) BLOC with high efficiency and high power in electric motion vehicle is increasing. IPM BLDC motor has permanent magnets in the rotor. Because it has two different flux paths, magnetic reluctance differences are generated in d-axis and q-axis. As the result of the inductance differences that are generated by the saliency(magnetic reluctance differences) in the rotor, the motor has structure advantage that has the additional reluctance torque except a magnet torque and because magnet is situated inside the rotor, the mechanical structure is strong. Therefore IPM BLDC motor makes possible to have high speed and high power. This paper presents a design and characteristics analysis of IPM BLDC motor for electric vehicle. To design IPM BLDC motor, surface mounted permanent magnet(SPM) BLDC motor is used as the initial design model. According to the shape-ratio() of permanent magnet, the characteristic of IPM BLDC motor is analyzed by Finite element method (FEM). Characteristics analysis results of the designed motor are compared with the experimental results.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.55 no.1
• /
• pp.33-38
• /
• 2006

This paper proposes a simple MPPT control scheme of a based Current-Control-Loop system that can be obtains a lot of advantage to compare with another digital control method, P&O(Perturbation and Observation) and IncCond(Incremental Conductance) algorithm, that is applied mostly a PV system. An existent method is needed an expensive processor such as DSP that calculated to change the measure power of a using current and voltage sensor at the once. Therefore, it is applied a small home power generation system that required many expenses. But, a proposed method is easy to solve the cost reduction and power unbalance Problems that it is used by control scheme to limit error of a current control of common sensor. This proposed algorithm had verified through a simulation and an experiment results on battery charger using PIC that is the microprocessor of a low price.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.50 no.2
• /
• pp.59-64
• /
• 2001

The distribution of current in the conductors influenced by the armature geometry and velocity is an important parameter for determining performance of an electromagnetic launcher(EML). the electric current in the early launching stage tends to flow on the outer surfaces of the conductors, resulting in very high local electric current density. However, the tendency for current to concentrate on the surface is driven by the velocity skin effect later in launching stage. The high current density produces high local heating and, consequently, increases armature wear which causes several defects on EML system. This paper investigates the effects of rail/armature geometry on current density distribution, launcher inductance gradient (L'), and contact force. Three geometrical parameters are used here to characterize the railgun system. These are the ratio of contact length to root length, relative position of contact leading edge to root trailing edge, and the ratio of rail overhang to the rail height. The distribution of current density, L', contact force between various configurations of the armature and the rail are analyzed and compared by using the EMAP3D program.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.48 no.9
• /
• pp.467-475
• /
• 1999

This paper presents an analysis method of a forward converter, using both the finite element method considering the external circuit and a state variables equation. The converter operates at 50kHz and its one period is divided into two modes for the simplicity of the analysis. In the first mode, the switching transistor turns on and an input power is transferred into the load by the electromagnetic conversion action of a ferrite transformer. In the second mode, the switching transistor turns off and the stored energy in an inductor is delivered to the load, and the transformer core is demagnetized by the reset winding current. In this paper, time-stepping finite element method taking into account the on-state electrical circuit of the converter in used to analyze both the electrical circuit and electromagnetic field of the magnetic device during the first mode and the demagnetization period of the transformer core. Then a state variables equation for the circuit which the inductor current flows is constituted and solved during the second mode. As a result, the simulation results have been good agreement with the results obtained form experiment.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.48 no.9
• /
• pp.484-489
• /
• 1999

This paper deals with the design and fabrication of a heater-trigger type high-Tc superconducting power supply system, and characteristics have been analyzed through experiments. The high-Tc superconducting power supply consists of two heater trigger and electric magnet, and YBCO superconducting bulk. In this experiment, 0.6T class magnet and dc 2.3A heater current are used, and the current-pumping characteristics have been analyzed with computer aided sequence control system. Hall sensors are installed on the YBCO bulk and in the center of iron core in order to analyze the effect of the flux-pumping on the system with when magnet flux changes its value. In this experiment, maximum pumping-current has been achieved to about 6.6 amps.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.53 no.2
• /
• pp.114-122
• /
• 2004

This paper presents a novel single-stage active-clamp type high frequency resonant inverter. The proposed topology is integrated full-bridge boost rectifier as power factor corrector and active-clamp type high frequency resonant inverter into a single-stage. The input stage of the full-bridge boost rectifier works in discontinuous conduction mode(DCM) with constant duty cycle and variable switching frequency. So that a boost converter makes the line current follow naturally the sinusoidal line voltage waveform. By adding additional active-clamp circuit to conventional class-E high frequency resonant inverter, main switch of inverter part operates not only at Zero-Voltage-Switching mode but also reduces the switching voltage stress of main switch. Simulation results have demonstrated the feasibility of the proposed high frequency resonant inverter. Characteristics values based on characteristics estimation through circuit analysis is given as basis data in design procedure. Also, experimental results are presented to verify theoretical discussion. This proposed inverter will be able to be practically used as a power supply in the fields of induction heating applications, fluorescent lamp and DC-DC converter etc.