Cherl-Jin Kim

Torque Ripple Improvement for Interior Permanent Magnet Synchronous Motor Considering Parameters With Magnetic Saturation

This paper presents a method to reduce torque ripple considering parameters with magnetic saturation. To estimate parameters of inductances for interior permanent magnet synchronous motor (IPMSM), the proposed method uses recursive least square (RLS) estimation algorithm. The estimated inductances are used for calculating torque and DC link voltage. Using the torque and the DC link voltage estimators, this control method can reduce torque ripple of IPMSM because of keeping linearity of inverter output. Therefore, the torque control system can achieve precise torque control. The proposed control method is verified by computer simulation and experiment.

Magnetic properties of new Nd-Fe-B nanocrystalline with /spl alpha/-Fe as main phase

The /spl alpha/-Fe based Nd-Fe-B magnet with low Nd content has been investigated to develop a new type of rare earth magnet. The amorphous Nd/sub 4/Fe/sub 85.5/B/sub 10.5/ alloy prepared by a rapid quenching technique was crystallized to form only two phases: /spl alpha/-Fe as the main phase, and Nd/sub 2/Fe/sub 14/B as the secondary phase, The coercivity and remanence of the studied alloy were 95.5 kA/m and 1.2 T, respectively. The additions of Mo and Cu to Nd/sub 4/Fe/sub 85.5/B/sub 10.5/ alloy reduced the mean grain size and increased the coercivity up to 207 kA/m. Furthermore, the substitution of 8 at% Co for Fe in Nd/sub 4/Fe/sub 82/B/sub 10/Mo/sub 3/Cu/sub 1/ improved the coercivity, remanence, and Curie point. The coercivity, remanence, and energy product of the Nd/sub 4/Fe/sub 74/Co/sub 8/B/sub 10/Mo/sub 3/Cu/sub 1/ alloy were 219 kA/m, 1.4 T, and 103.5 kJ/m/sup 3/, respectively.

Effects of Dv on magnetic properties of /spl alpha/-Fe/Nd/sub 2/Fe/sub 14/B type alloy

The effects of Dy content on magnetic and microstructural properties of melt-spun (Nd/sub 1-x/Dy/sub x/)4(Fe/sub 0.9/Co/sub 0.1/)/sub 86/B/sub 6/Nb/sub 3/Cu alloys have been investigated. The energy product of the alloys decreases with the increase of Dy content, while the coercivity increases up to 2.64 kOe at x=0.3. At a fixed annealing time condition, the optimum annealing temperature increases by Dy substitution, and grain coarsening occurs in the alloys with high Dy content. The deterioration of hard magnetic properties by Dy substitution is due to the decrease of exchange interaction between a-Fe and (Nd,Dy)/sub 2/Fe/sub 14/B phases by grain coarsening.

Magnetic properties of (Fe,Co)-B-Al-Nb alloys with ultrafine grain structure

The magnetic properties of (Fe,Co)-B-Al-Nb alloys prepared by rapid solidification process have been studied for the development of a new type Fe-based nanocrystalline alloy. Microstructure composed of ultrafine bcc Fe(Co) has been obtained directly from the rapid solidification by adding 10 at.% Al to (Fe/sub 0.85/Co/sub 0.15/)/sub 80/B/sub 20/ alloy. Furthermore, the addition of 2/spl sim/6 at% Nb to (Fe/sub 0.85/Co/sub 0.15/)/sub 70/B/sub 20/Al/sub 10/ alloy decreases the saturation magnetostriction below 5 ppm. Heat treatment of as-prepared alloys further improves its soft magnetic properties in high frequency range. (Fe/sub 0.85/Co/sub 0.15/)/sub 70/B/sub 18/Al/sub 10/Nb/sub 2/ alloy annealed at 400/spl deg/C for 1 h shows the microstructure composed of ultrafine grains of about 8 nm and the most improved magnetic properties among the prepared alloys. >

Nonlinear observer based control of PEM fuel cell systems

In this paper, the nonlinear observer based controller will be developed for PEM fuel cell system. Nonlinear model of PEM fuel cell system is introduced to study the design problems of observer. Sliding mode observer and nonlinear state observer are designed to estimate the system states such as supply manifold pressure, Oxygen pressure, Hydrogen pressure, return manifold pressure, etc. These states will be used to design the observer based state feedback controller.

A study on irreversible permanent magnet demagnetization in flux-reversal machines

Flux-reversal machine (FRM) is a new doubly-salient stator-permanent magnet (PM) machine with flux linkage reversal in the stator concentrated windings. The simple structure makes it cost effective and suitable for mass production. Also, the FRM has permanent magnets parallel to the stator magnet flux lines and thus is much more difficult to demagnetize. However, in actual application fields such as factory automation and a home appliance, the FRMs adopt permanent magnets with a low intrinsic coercivity and a narrow thickness. In this paper, we especially concentrate on the irreversible demagnetization characteristic of the permanent magnet. To analyze the characteristics of the FRM, a two-dimensional finite-element method (2D FEM) considering the nonlinear analysis of the permanent magnet is used.

Robust Torque Control of DC Link Voltage Fluctuation for SynRM Considering Inductances With Magnetic Saturation

This paper presents the control method that inverter output keeps to linear to reference voltage of Synchronous Reluctance Motor (SynRM) using DC Link voltage Synthesis. This method is reduced torque ripple considering parameters with magnetic saturation. To estimate parameters of inductances for SynRM, the proposed method uses recursive least square (RLS) estimation algorithm. The estimated inductances are used for calculating torque and DC link voltage. The Inverter output voltage cannot be displayed to linear about inverter reference voltage if Real DC Link voltage is different from DC Link voltage of PWM amplitude. Also, the over-modulation is linearity broken if reference voltage is out of range. Torque ripple generates the vibration and noise of a motor. This paper proposes the control method so that the torque ripple decreases and the linearity of inverter output keeps using the DC Link voltage Synthesis. The proposed control method is verified by computer simulation and experiment.

Sliding Mode Current Controller Design for Power LEDs

High-brightness LED control is required for stable operation, thus the driver and control system must be designed to deliver a constant current to optimize reliability and ensure consistent luminous flux. In this paper, the sliding mode current controller is designed to adjust the illumination density of power LEDs. The controller design model of power LEDs, including its driving circuit, is proposed to realize the dimming control of power LEDs. A buck converter is introduced to drive the power LEDs and reduce the input voltage to a lower level. The sliding mode software controller is implemented to adjust the dimming of power LEDs. The proposed strategy for driving power LEDs is investigated and comparatively studied by experiments.

Nonlinear state feedback control of PEM fuel cell systems

In this paper, the nonlinear state feedback controller will be developed for PEM fuel cell system. Nonlinear model of PEM fuel cell system is introduced to study the design problems of observer. Sliding mode observer and nonlinear state observer are designed to estimate the system states such as supply manifold pressure, Oxygen pressure, Hydrogen pressure, return manifold pressure, etc. These states will be used to design the state feedback controller.

A study on the power LEDs drive circuit design with asymmetrical half-bridge resonant converter

Recently white light-emitting diode (LED) has very attractive attention as a backlight for LCD display and lighting sources. The series-parallel connected LEDs must be driven from a current source because their forward voltage varies, as a result the brightness changes depending on the forward current increases. In this paper, the suitable LED driving system is proposed for LED lighting sources. The driving system is consist of high power factor correction circuit and isolated constant current DC-DC converter with high efficiency.