Ki-Hyeon Park

Laminated magnetic flux sensor for thick-steel-plate control

This paper presents a rugged magnetic flux sensor, which can measure the thickness of steel plates and can operate reliably in the poor environment of a warehouse for thick steel plates. The sensor, consisting of a laminated sensing plate and a sensing coil, has a size of 6/spl times/6 cm/sup 2/, and it is embedded inside the core of a lifting magnet. Depending on the thickness of steel plates attached on the lifting magnet, the magnetic permeability of the core and the sensing plate changes. The thickness of steel plates is indirectly measured by measuring the changes in the magnetic flux density of the sensor. The measurement sensitivity of the magnetic flux sensor with laminated sensing plate is much better than that of a sensor with a solid sensing plate. With a proper procedure for securing measurement reliability, it is demonstrated that the sensor can measure up to 13 sheets of 6-mm steel plate.

A New Driving Method of the Magnetron Power Supply for a Sulfur Plasma Lamp

This paper presents a new driving method for a sulfur plasma lamp in low-power applications. The newly developed magnetron power supply (MPS) is a series-resonance type with a full-bridge topology controlled by the phase shift to track the beam current of the magnetron. To drive the sulfur plasma lamp optimally, the MPS should: 1) provide peak power above a discharge condition to excite the sulfur plasma lamp, and 2) allow average power control of the light dimmer while satisfying condition 1. The newly developed driving method uses the burst mode, which enables both peak and average power controls to satisfy these conditions. Furthermore, a magnetizing current offset balancer is developed; it guarantees zero-voltage switching of all field-effect transistors, although the MPS operates in the burst mode. Thus, the proposed method provides easy lighting and relighting under optimized conditions with high efficiency. The power of the MPS delivered by the proposed method reached 1.6 kW with variable average power of 200 ~ 400 W by adjusting burst-on time proportionally. Experimental results proved the feasibility of the proposed driving method.

Design and fabrication of X-band AlGaAs/GaAs power HBTs

We performed systematical thermal design and fabricated X-band 0.5 W class power HBTs. Based on the thermal design, we adopted an HBT with emitter-to-emitter spacing of 30 /spl mu/m as a standard device. The collector-emitter breakdown voltage is 16 V indicating that 8 V operation is possible. f/sub t/, f/sub max/ and output power of the HBT at 10 GHz are 67, 58 GHz and 0.58 W, respectively. Various kinds of HBTs with different structures have been studied for reducing the thermal effects and we will present the dominant effect on thermal problems and the measurement data for thermal design guide.

Sensorless Vector Control of Induction Motors for Wind Energy Applications Using MRAS and ASO

Speed sensorless modes of operation are becoming standard solution in the area of electric drives. This paper presents flux estimator and speed estimator for the speed sensorless vector control of induction motors. The proposed sensorless methods are based on the model reference adaptive system (MRAS) observer and adaptive speed observer (ASO). The proposed speed estimation algorithm can be employed in the power control of grid connected induction generator for wind power applications. Two proposed schemes are verified through computer simulation PSIM and compared their simulation results.

Micro-mover Development and Test in the PAL-XFEL

Abstract Two micro-movers, which are able to control the horizontal, vertical and longitudinal positions as well as the yaw and pitch angles remotely, were developed and installed in the PAL-XFEL linac. The solenoid micromover in the gun section allows beam-based alignment of an electron beam to the solenoid field and the gun RF field. The X-band cavity micro-mover minimizes the transverse wake field effect caused by transverse misalignment between the beam and X-band cavity. Two micro-movers has similar specifications and the same mechanism, but the sizes are different from each other. In this paper, we present the design, manufacture and test results of the micro-movers.

Status of the PAL-XFEL undulator program

Pohang Accelerator Laboratory (PAL) is developing a 0.1 nm SASE based FEL based on 10 GeV S-band linear accelerator named PAL-XFEL. At the first stage, PAL-XFEL needs two undulator lines for photon source. The hard Xray undulator line requires 18 units of 5 m long hybrid-type conventional planar undulator and soft X-ray line requires 6 units of 5 m long hybrid type planar undulator with additional few EPUs for final polarization control. PAL is developing undulator magnetic structure based on EU-XFEL concepts. The key parameters are min pole gap of 8.3 mm, with period length 26 mm (HXU), 35 mm (SXU), and 5.0 m magnetic length. . In this report, the prototyping, and the development of pole tuning procedure, the impact of the background field error, and the effects of the girder bending on the optical phase error will be presented.

Design of Switching Magnet for 20-MeV Beamlines at PEFP

The PEFP (Proton Engineering Frontier Project) proton linac is designed to have two proton beam extraction lines at the 20-MeV and 100-MeV end. The 20-MeV extraction line is branched out into 5 beamlines by using the switching magnet. The magnet bends the proton beam by +20, +10, 0, -10, -20 degrees, respectively, and has an AC frequency of 2.5 Hz with a programmable ac power supply. It employs an H-shape, 0.45 T magnetic fields, 500 mm effective length, and 50 mm pole gap. Laminated steel of 0.5 mm reduces the eddy currents in the yoke, but some heat radiation from the stainless steel of vacuum chamber is inevitable. This paper presents the magnet specification and primary design.