Higher Power Factor Values Research Articles

Preparation and transport properties of aqueous sol-gel synthesized NaCo2O4-

We have successfully prepared thermoelectric materials NaCo2O4−δ at lower temperature (700°C) using aqueous sol-gel methods. We find that the electrical resistivity and thermopower of NaCo2O4−δ depend strongly on the sintering temperature and partial pressure of oxygen. The oxygen content of NaCo2O4−δ is found to decrease with increasing sintering temperature. The sample prepared at the combination of 700°C and pure flowing oxygen exhibits the highest value of power factor.

Heat Characteristics of V94.2 Gas-Turbine Units Operating at the PGU-450T Combined-Cycle Plant of the North-West Cogeneration Plant of St. Petersburg

Tests of V94.2 gas-turbine units (GTU) of the first PGU-450T plant of the North-West Cogeneration Plant of St. Petersburg are described. The parameters of the GTU and the regular features of their variation are determined in a wide range of operating conditions from idle running to full load. The GTU are characterized by high pressure losses in a cycle, high values of specific power and yield factor, and low concentrations of toxic gases in combustion products at operating modes ranging from 50% load to full load. Quite high efficiencies of the turbomachines are obtained under conditions close to the design ones. The maximum power of 173 MW is attained at a temperature of –10°C and GTU efficiency of 34.5%.

Thermoelectric Properties of Ce Based Filled Skutterudite Phosphides

Polycrystalline samples of filled skutterudite phosphide LaxCe1-xRu4P12(0 ≤ x ≤ 0.3) and LaxCe1-xOs4P12(0 ≤ x ≤ 0.5) were synthesized using high temperature and high-pressure techniques. The samples were characterized by x-ray diffractometry. The thermoelectric properties were measured. These properties include electrical resistivity, the Seebeck coefficient and thermal conductivity. La doping Ce based filled skutterudite phosphides enhanced the high power factor value of 0.7×10-3[W/K2m] due to a considerable decrease in the value of resistivity and thermal conductivity without much decrease in the Seebeck coefficient. It has been noticed that doping of more than one rare earth element caused a decrease in the thermal conductivity by increasing randomness and rattling effects.

Hysteresis and reluctance electric machines with bulk HTS elements.Recent results and future development

Two new types of HTS electric machine are considered. The first typeis hysteresis motors and generators with cylindrical and disc rotorscontaining bulk HTS elements. The second type is reluctance motors withcompound HTS-ferromagnetic rotors. The compound HTS-ferromagnetic rotors,consisting of joined alternating bulk HTS (YBCO) and ferromagnetic (iron)plates, provide a new active material for electromechanical purposes. Suchrotors have anisotropic properties (ferromagnetic in one direction anddiamagnetic in the perpendicular one). Theoretical and experimental resultsfor HTS hysteresis and reluctance motors are presented. A series of hysteresisHTS motors with output power rating from 1 kW (at 50 Hz) up to 4 kW (at400 Hz) and a series of reluctance HTS motors with output power 2-18.5 kW (at50 Hz) were constructed and successfully tested. It was shown that HTSreluctance motors could reach two to five times better overall dimensions andspecific power than conventional asynchronous motors of the same size and willhave higher values of power factor (cos φ⩾0.7 to 0.8).

Hysteresis and reluctance electric machines with bulk HTS rotor elements

Two new types of HTS electric machines are considered. The first type is hysteresis motors and generators with cylindrical and disk rotors containing bulk HTS elements. The second type is reluctance motors with compound HTS-ferromagnetic rotors. The compound HTS-ferromagnetic rotors, consisting of joined alternating bulk HTS (YBCO) and ferromagnetic (iron) plates, provide a new active material for electromechanical purposes. Such rotors have anisotropic properties (ferromagnetic in one direction and diamagnetic in perpendicular one). Theoretical and experimental results for HTS hysteresis and reluctance motors are presented. A series of hysteresis HTS motors with output power rating from 1 kW (50 Hz) up 4 kW (400 Hz) and a series of reluctance HTS motors with output power 2-9 kW (50 Hz) was constructed and successfully tested by the cooperation of MAI (Moscow, Russia) and IPHT (Jena, Germany). It was shown that HTS reluctance motors could reach 2-5 times higher specific output than conventional asynchronous motors of the same size and will have higher values of power factor (cos/spl phi//spl ges/0.7-0.8).

Search for New Semiconductors for High Temperature Applications:The BaPb1-x BixO3 System

ABSTRACTBaPbl-xBixO3 phases with 0.6⋚ x⋚ 1.0 were synthesized by high temperature solid state reaction. Powder X-ray diffraction measurements show that all compositions are in single phase. Linear variation of lattice parameter is observed in BaPb1-xBixO3 with change in x indicating the random distribution of Pb in Bi sites. The activation energies for conduction of phases with x=0.8−0.6 obtained from ρ −T plots are same suggesting that the band gap does not change for compositions with x-0.8−0.6. The low activation energy obtained for BaBiO3 can be attributed to the structure of the compound. S versus (1000/T) data of x=1.0−0.8 exhibit a two-slope behavior. The orthorhombic to cubic phase transition could be the possible reason for the high power factor values of BaBiO3.

Optimization Studies with Form-Wound Stator Groundwall Insulation

The effect of increasing the micabond resin content on the impregnation characteristics and electrical properties of a solventless epoxy resin impregnated groundwall insulation has been explored using small copper tube test samples. In this study, six different micabond materials, consisting of cycloaliphatic epoxy, bisphenol 'A' epoxy, epoxy-novolac, glycidyl-ester, and polybutadiene resins, were evaluated by increasing the bond resin content up to 24% in the mica wrapper. Impregnant retention and drainage data were obtained for each micabond material with the solventless epoxy resin. Retention efficiency (R/D) values were also computed and, with few exceptions, were found to drop sharply with increasing micabond resin content. The power factor data, obtained at 150°C and 1 kV, show that some of the micabond resins, e.g. cycloaliphatic epoxy, bisphenol 'A' epoxy and polybutadiene, exhibit lower power factors with increasing micabond contents, whereas others, such as epoxy-novolac micabond resins, show higher power factor values when bond resin content is increased. It is concluded that the best compromise of electrical compatibility and impregnation efficiency is obtained when the micabond resin content is in the range of 12 to 18% for most of these developmental resins.

Air and moisture versus paper insulation

THIS is the third of a series of studies into the still open question of the influence of residual air and moisture upon the properties of impregnated-paper insulation. The influence of residual moisture was found to be universally bad and increasing amounts of such moisture are immediately reflected in higher values of power factor and loss and in other evidence of instability. One of the most striking results of the earlier studies was the relatively small effect of residual air upon the shape of the voltage-power factor curves. The shape of these curves was not appreciably affected in the range of evacuation pressure from 1 to 10 cm. Hg. abs. and furthermore the curves were flat up to 300 volts per mil and 50 deg. cent. Only at impregnation pressures above 25 cm. Hg. do the typical rising power factor-voltage curves become evident. Upon dissection, dryness and gas voids always were associated with rising power factor-voltage curves, and apparently-excellent impregnation with the flat curves.