Experimental determination of suboptimal parameters for energy-efficient control of an induction motor

The article presents the results of experimental studies of the automatic speed control system (ASCS) of an induction motor (IM). Preliminary experimental studies have shown that the stator current minimum (power factor) is a suboptimal criterion. Optimal in terms of control is the rated power factor. Tests of IM with a thyristor voltage converter (TVC), as a power source, were conducted on an installation created at the department. A mathematical model of ASCS IM corresponding to the experimental setup has been developed. To determine the main functional dependences of IM, such as stator voltage, stator current, power factor, torque on the shaft, a program for approximating experimental data by polynomials was developed. Using the developed mathematical model, the regulatory characteristic of IM that was optimal from an energy point of view was obtained. The necessary indicators of IM and TVC are determined (thyristor control angle, stator voltage, stator current) to change existing settings in order to save electric energy. The results of experimental studies are presented, the graph shows an optimized version of the form of the regulatory characteristic according to the criterion of minimum electric energy consumption.

MATHEMATICAL MODEL OF ESTIMATION THE DYNAMIC PARAMETERS OF MACHINE AND TRACTOR UNIT’S ENGINE UNDER UNSTEAD LOAD

The article provides an analysis of the existing methods and techniques for assessing the dynamic characteristics of engines of mobile machines, and also presents theoretical calculations for estimating the dynamic performance of an machine and tractor unit’s engine under unsteady load. The proposed mathematical model describes the change in the performance of the engine of machine and tractor unit with a linear law of loading and allows you to compare an engine’s operation at unsteady load with the ideal. The quasi-dynamic characteristic was laid as the theoretical basis for study to assess the dynamic performance of machine and tractor unit’s engine under unsteady load. Comparison of the dynamic performance of engines at unsteady load with ideal performance, which have no dynamic losses. It is proposed to apply the “quasi-dynamic” characteristics. The quasidynamic (ideal) characteristic is called - the change in the performance of machine and tractor unit’s engine, in the transition process, occurring in accordance with the change in the frequency of rotation of the crankshaft on the stationary characteristics. The mathematical model for estimating the dynamic performance of an machine and tractor unit’s engine using a correcting branch with an unsteady load is experimental equations for load buildup. Theoretical relationships have been developed for evaluating the dynamic performance of an engine with an unsteady load on the correcting branch of the regulatory characteristic. Using the proposed theoretical dependences, it is possible to carry out theoretical studies of the effect of load on the dynamic performance of an machine and tractor unit’s engine and determine the total dynamic losses.

Effects of sepiapterin and 6-acetyldihydrohomopterin on the guanosine triphosphate cyclohydrolase I of mouse, rat and the fruit-fly Drosophila

The regulation of GTP cyclohydrolase I would lead to the regulation of tetrahydrobiopterin, an important cofactor for synthesis of neurotransmitters. In an attempt to extend a previous finding [Bellahsene, Dhondt, & Farriaux (1984) Biochem. J. 217, 59-65] that GTP cyclohydrolase I of rat liver is inhibited by subnanomolar concentrations of reduced biopterin and sepiapterin, we found that this could not be verified with the enzyme from mouse liver, fruit-fly (Drosophila) heads or, indeed, from rat liver. It was shown, however, that 12 microM-sepiapterin inhibited mouse liver GTP cyclohydrolase I. Another compound, namely 6-acetyldihydrohomopterin, was also employed in the present study to explore its effect on enzymes that lead to its synthesis in Drosophila and for effects on mammalian systems; at 2-5 microM this compound was shown to stimulate one form of mouse liver GTP cyclohydrolase I and then to inhibit at higher concentrations (40 microM). Neither sepiapterin nor 6-acetyldihydrohomopterin caused any effect on the Drosophila head enzyme. On the other hand, the sigmoid GTP concentration curve for the Drosophila enzyme may indicate a regulatory characteristic of this enzyme. Another report, on the lower level of GTP cyclohydrolase I in mutant mouse liver [McDonald, Cotton, Jennings, Ledley, Woo & Bode (1988) J. Neurochem. 50, 655-657], was confirmed and extended. Instead of having 10% activity, we find that the hph-1 mouse mutant has less than 2% activity in the liver. These studies demonstrate that micromolar levels of reduced pterins may have regulatory effects on GTP cyclohydrolase I and that a mouse mutant is available that has low enough activity to be considered as a model for human atypical phenylketonuria.