To obtain a transparent and effective solution of p-hydroxybenzoic acid esters (parabens), the use of 2-hydroxypropyl-beta-cyclodextrins (2-HP-beta-CyDs) as solubilizers with different degrees of substitution (D.S.) was surveyed. 2-HP-beta-CyDs significantly increased the aqueous solubility of four kinds of parabens (methyl < ethyl < propyl < butyl esters), where the solubilizing ability decreased with an increase in the D.S. of the 2-hydroxypropyl group in beta-CyD. The antimicrobial activity of the parabens tended to decrease by complexation with 2-HP-beta-CyDs. However, the activity could be maintained by lengthening the alkyl chain of the parabens. 1H- and 13C-nuclear magnetic resonance and circular dichroism spectroscopic studies suggest that the hydrophobic alkyl moiety of butyl paraben is preferably included in the cavity, and the phenol group extrudes from the cavity. The present results suggest that a suitable combination of 2-HP-beta-CyDs and hydrophobic, longer alkyl parabens is useful for the preservation of liquid formulations.
Large capacity motor drive equipment, especially those with low harmonics and high efficiency, are in demand in the industrial field. In general Voltage Source Inverters (VSI) have low harmonics and high efficiency and have been widely applied in many steel plants. However, the cycloconverter drives which were applied in 1980's are still operating in many steel plants. The cycloconverter has low power factor and it is necessary to include harmonic filters to reduce the input power harmonics, making the whole equipment larger. Compared to the conventional cycloconverter, IGBT/IEGT VSI has the benefits of high input power factor and better speed control accuracy, including motor and load response. Moreover, the drive footprint is significantly smaller. Also, some existing cycloconverter drives have forcing voltages around 3600V. Until now there was no drive equipment that could directly replace all previous AC drives in both capacity and voltage. The rated capacity of the latest individual drive module is 9MV A with a maximum output of 3650V. With a power density of 1.3MV A/m 3 this compact structural configuration offers space-saving advantages for new and upgraded installations.
Many large capacity motor drive equipments have been used in the steel plants. High efficiency motor drive equipments are required in the industrial fields. On the other hand, the replacement demand of cycloconverter to VSI (Voltage Source Inverter) is also increasing. Normally, the VSI such as IGBT (Insulated Gate Bipolar Transistor) I IEGT (Injection Enhanced Gate Transistor) inverter has low-harmonics and high-efficiency. So, it has spread widely now. In this paper, it is introduced high efficiency and large capacity 3-level IEGT inverter for steel plant application. It is realized 6MV A rated output capacity. With the series line-up of 3-level IEGT inverter, it is possible to combine with the early development of 9MV A IEGT inverter. Moreover, it has the flexibility to connect with a common converter and several numbers of inverters.
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