Showing papers by "Romanian Academy published in 1969"

On the structure of dissolving thin liquid films

Abstract: The structure of thin circular films, formed over a flat water surface during the dissolving (influenced by surface forces) of isobutanol, is examined by performing film thickness and surface velocity measurements. The thicknesses were obtained by light absorption determinations, and the velocities by a stroboscopic method. The film profiles and the dynamic wetting angles obtained differ markedly from those corresponding to a static lens. This is explained by considering the equilibrium between dynamic surface tensions instead of that between static surface tensions.

Wide-Range Speed Control of Three-Phase Squirrel-Cage Induction Motors Using Static Frequency Converters

Abstract: An equipment is presented for speed control of three-phase squirrel-cage induction motors supplied through a thyristor converter directly from the mains (the European 50-Hz system) by controlling the frequency and voltage magnitude. Thus a continuous speed control system is achieved, corresponding to a frequency range of from 2.5 to 85 Hz. Speed control is at a constant torque, up to the motor frequency rating (50 Hz), and at a constant power over this frequency. The system configuration is described, a brief analysis of the control loop parameter adjustment is given, and the experimental results are discussed. Finally, the general characteristics of the method are presented.