Showing papers by "Jee-Hoon Jung published in 2007"

Theoretical analysis and optimal design of LLC resonant converter

Abstract: A LLC resonant topology is analyzed to derive efficiency and cost optimal design for wide input ranges and load variations In the LLC converter, a wide range of output power is controlled with only a narrow variation in operating frequency since this converter is capable of both step-up and step-down In addition, ZVS turn-on and ZCS turn-off of MOSFETs and diode rectifiers can be achieved over the entire operating range Finally, the inductance of a resonant tank in the primary side can be merged in the main power transformer by resonant inductance and the absence of the secondary filter inductor makes low voltage stress on secondary rectifier and cost-effective property DC characteristics and input-output response in frequency domain are obtained with the equivalent circuit derived by first harmonic approximation (FHA) method In addition, operational principles are explained to show the ZVS and ZCS conditions of primary switches and output diode rectifiers, respectively Efficiency and cost optimal design rules of the LLC resonant converter are derived by a primary resonant network, operating frequency, and dead time duration Proposed analysis and designation are proved by experimental results with a 400 W LLC resonant converter

Erosion Models of Rotor Bar and End Ring Faults in Progress to Diagnose Induction Motor Status

Abstract: Erosion models of rotor bar and end ring segment in induction motors are presented for diagnosing induction machines containing an abnormal rotor bar and end ring faults in progress. The leakage inductance and resistance of the rotor bar and end ring segment are varied during the erosion process. Consequently, the variation causes the rotor asymmetry which induces abnormal harmonics in the stator current spectra. The leakage inductances of the erosion models are derived by the Ampere's law. The winding function method (WFM) is used to conveniently calculate the machine inductance, and the slot width effect (SWE) of rotor bars is concerned more practical motor model. By the erosion models, it is shown that the rotor bar and end ring faults in progress are detectable by the motor current signature analysis (MCSA). Simulated and experimental results are presented to validate the proposed erosion model with 3.7 kW, 3-phase, and squirrel cage induction motors.