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    An analysis of iron loss supplied by sinusoidal, square wave, bipolar PWM inverter and unipolar PWM inverter
    (2007-12-01)
    Khluabwannarat, P.
    ;
    Thammarat, C.
    ;
    Tadsuan, S.
    ;
    Bunjongjit, S.
    This paper presents a comparison of iron loss with sinusoidal supply (50 Hz) 1-phase square wave inverter supply 1-phase bipolar PWM inverter and 1-phase unipolar PWM inverter. In the experiment, using 0.5 mm.-thick Non-oriented magnetic steel and by setting equal maximum fundamental magnetic density for each test procedure, with 0.3, 0.45, 0.6, 0.9-modulation indexes and 1, 3 kHz. -inverter switching frequencies results show that the iron loss by 1-phase PWM inverter supply is less than other inverters, so this study is useful for selecting the PWM inverter with a lower iron loss. © 2007 RPS.
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    Finite element analyses for a study of hepatic cancer tissue destruction using monopolar and bipolar radio-frequency ablation
    (2005-11-28)
    Tungjitkusolmun, S.
    ;
    Boontaram, A.
    ;
    Lertprasert, P.
    ;
    Krairiksh, M.
    This paper presents three-dimensional finite element analyses of radio-frequency hepatic tumor ablation. The analyses performed in this paper are composed of two systems. In the first system, the simulation was of monopolar ablation (one needle), while the second system was the simulation of bipolar ablation (two needles). We performed a preliminary study of thermal and electrical distributions of both systems. Additional simulations of bipolar ablation were performed to investigate the effect of spacing distance between two needle electrodes (2 cm, 3 cm, 4 cm, and 5 cm). The ablation duration used in all cases was 10 min, and the controlled maximum temperature was set to 90°C. From the results, the electric field in monopolar ablation appeared to be distributed uniformly between the electrode and the ground surface, but the electric field in bipolar ablation was focused in the regions between the two electrodes. For bipolar ablation, when the distances between the electrodes were 2 cm and 3 cm, the lesion created was contiguous and covered the areas surrounding both electrodes. However, when the distances between the electrodes were 4 cm and 5 cm, the lesions created were not contiguous and shaped similar to performing two monopolar ablation operations.
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    A Fully Independently Adjustable, Integrable Simple Current Controlled Oscillator and Derivative PWM Signal Generator
    (2003-01-01)
    Siripruchyanun, Montree
    ;
    Wardkein, Paramote
    A simple circuit scheme, able to generate square/triangular wave, is proposed. Its advantages are that oscillation frequency and amplitudes of the proposed circuit do have a small range of temperature drift. Electronic adjustments of them can be obtained with a wide sweep range and DC offset adjustment available. In addition, the proposed scheme can produce frequency-constant derivative of PWM signal without an additional device requirement. It is very appropriate for, with simple circuit details, not only circuit implementation but also monolithic fabrication. The PSPICE simulation results through bipolar technology are given here, they show good performance of the proposed circuit.