THE THEORY OF SOME A-C. COMMUTATOR MOTORS WITH SERIES CHARACTERISTICS: I. THE REPULSION MOTOR

1942 ◽  
Vol 20a (5) ◽  
pp. 49-70
Author(s):  
E. G. Cullwick
Keyword(s):  
Power Factor ◽  
Maximum Power ◽  
Experimental Results ◽  
Finite Speed ◽  
Three Phase ◽  
Maximum Power Factor ◽  
Starting Torque ◽  
General Method

A general method, using "full reactances", is applied for developing the theory of the simple repulsion motor, the compensated repulsion motor, and the three-phase series motor. The effect of the currents induced in the armature turns short-circuited by the brushes is included, and is shown to affect profoundly the operation of the motors. Graphical constructions for the current loci are given, together with methods of measuring the various reactances, and of accounting for the effect of saturation. Experimental results for a three-phase series motor are included and compared with calculated values.Part I, published below, deals with the simple repulsion motor. Neglecting the effects of the coils short-circuited by the brushes, the usual well known results are obtained, and the position of the brushes for maximum starting torque is studied. The currents circulating in the coils short-circuited by the brushes are then found to have the following effects:(a) The performance of the motor, for a given current, is improved at speeds below synchronism, and is impaired at speeds above synchronism.(b) The maximum power factor is found to occur at some finite speed, whereas, if the effect of the short-circuited coils is neglected the power factor is a maximum at infinite speed.(c) The no-load speed is considerably lower than that usually associated with series motors.The rise and fall of the currents in the coils short-circuited by the brushes is studied in the Appendix.

Transport Properties Of Doped CsBi4Te6 Thermoelectric Materials

1998 ◽  
Vol 545 ◽  
Author(s):  
Paul W. Brazis ◽  
Melissa Rocci ◽  
Duck-Young Chung ◽  
Mercouri G. Kanatzidis ◽  
Carl R. Kannewurf
Keyword(s):  
Transport Properties ◽  
Power Factor ◽  
Thermoelectric Materials ◽  
Material Characterization ◽  
Doping Concentration ◽  
Maximum Power ◽  
Maximum Value ◽  
Characterization Studies ◽  
Maximum Power Factor ◽  
Optimum Doping Concentration

AbstractIn previous investigations we have introduced a variety of new chalcogenide-based materials with promising properties for thermoelectric applications. The chalcogenide CsBi4Te6 was previously reported to have a high ZT product with a maximum value at 260K. In order to improve this value, a series of doped CsBi4Te6 samples has been synthesized. Current doping studies have been very encouraging, with one sample found to have a maximum power factor of 51.5 μW/cm·K2 at 184 K. This paper reports on material characterization studies through the usual transport measurements to determine optimum doping concentration for various dopants.

scholarly journals Efficiency Analysis on Small Sized Generators in Nigeria

2019 ◽  
Vol 2 (2) ◽  
pp. 37-44
Author(s):  
A. E. Airoboman ◽  
Mohammed A. S. Jibrin ◽  
J. O. Ademola ◽  
J. Oladokun ◽  
S. Ahmed ◽  
...  
Keyword(s):  
Power Factor ◽  
Experimental Analysis ◽  
Efficiency Analysis ◽  
Maximum Power ◽  
Experimental Results ◽  
Loading Conditions ◽  
Average Efficiency ◽  
Experimental Analyses ◽  
Potential Customers ◽  
Adequate Power

In this paper, efficiency analysis of small sized generators in Nigeria was considered. Experimental analyses were carried out on two (2) different samples of generators tagged “S” and “T” at different loading conditions (20%, 40%, 60% etc. of ratings) to ascertain the generators’ efficiencies as well as the maximum true power that could be drawn out from the generators. The experimental results are compared with the manufacturers ratings specified on the name plate of the generators. The results indicated an average efficiency of 44.9% and 55.7% for “T” and “S” respectively an indication that generator “S” is more efficient that “T”. The results also showed that the values of the power factor indicated on the generators are inaccurate as none of the generators could give the maximum power as indicated on their name plates based on the experimental analysis carried out. The generators selected were able to provide adequate power to the selected loads with efficiencies not up to 100% of the expected rated value of the generators. For generator “S” it was observed that the efficiency decreases from the highest rating to the lowest rating. Conclusively, this result suggests that portable generators dealers are taking advantage of the energy crises to importing generators not up to specifications to the Nigerian market at the expense of naïve customers. This paper recommends that proper standards and measures be put in place and enforced by the relevant authority for conformity of standards to all imported generators to save guard and protect the interest of potential customers and Nigerians.

Thermoelectric Properties of CoSb3 Nanoparticle Films

2011 ◽  
Vol 347-353 ◽  
pp. 3448-3455
Author(s):  
Ya Jun Yang ◽  
Xian Yun Liu ◽  
Xu Dong Wang ◽  
Mei Ping Jiang ◽  
Xian Feng Chen ◽  
...  
Keyword(s):  
Thermoelectric Properties ◽  
Power Factor ◽  
Room Temperature ◽  
Maximum Power ◽  
Vapor Transport ◽  
Growth Technique ◽  
Highly Efficient ◽  
Nanoparticle Films ◽  
Electrical Conductivities ◽  
Maximum Power Factor

Cobblestone-like CoSb3 nanoparticle films have been achieved via a catalyst-free vapor transport growth technique. The thermoelectric properties of the nanoparticle films were measured from room temperature to around 500 oC. The resultant CoSb3 nanoparticle films show high electrical conductivities due to clean particle surfaces. A maximum power factor reaches 1.848×10−4 W/mK2 at 440 oC. The discussed approach is promising for realizing new types of highly efficient thermoelectric semiconductors.

Microwave-assisted synthesis of Bi2Se3ultrathin nanosheets and its electrical conductivities

CrystEngComm ◽  
2014 ◽  
Vol 16 (19) ◽  
pp. 3965-3970 ◽  
Author(s):  
Haiming Xu ◽  
Gang Chen ◽  
Rencheng Jin ◽  
Dahong Chen ◽  
Yu Wang ◽  
...  
Keyword(s):  
Power Factor ◽  
Microwave Power ◽  
Maximum Power ◽  
Microwave Assisted Synthesis ◽  
Microwave Assisted ◽  
Electrical Conductivities ◽  
Maximum Power Factor

Ultrathin Bi2Se3nanosheets (30 nm) have been successfully fabricated with 1 kW microwave power for 1 minute. The maximum power factor of the sample can reach up to 157 μW m−1K−2at 523 K, which is larger than the samples with thicknesses ranging from 50 nm to 100 nm.

Electronic structure and electrical transport properties of MoS2 single-walled nanotubes based on first principles

2021 ◽  
Author(s):  
Wen Yang ◽  
Lili Wang ◽  
Yiming Mi ◽  
Guanghong Zhong ◽  
Qiuju Ma ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Transport Properties ◽  
Power Factor ◽  
Electrical Transport ◽  
Maximum Power ◽  
Boltzmann Transport ◽  
Electrical Transport Properties ◽  
Text Type ◽  
Maximum Power Factor ◽  
Transport Method

The work theoretically calculated the electronic structure and electrical transport properties of two configurations of single-walled MoS2 nanotubes: armchair nanotubes (ANTs) and zigzag nanotubes (ZNTs) based on the density functional theory and Boltzmann transport method. ANTs have an indirect one. while ZNTs have a direct bandgap structure. The Seebeck coefficient ([Formula: see text]), electrical conductivity ([Formula: see text] and power factor ([Formula: see text] were calculated as a function of carrier concentration, chemical potential and temperature using the Boltzmann transport method. The calculated power factor ([Formula: see text]) indicates that the most promising electronic properties were exhibited by [Formula: see text]-type ANTs and [Formula: see text]-type ZNTs. The [Formula: see text] of narrow bandgap (6, 6) (7, 7) (8, 8) semiconductors reached [Formula: see text], [Formula: see text] and [Formula: see text]WK[Formula: see text]m[Formula: see text] at room-temperature, respectively. (7, 7) nanotube have a maximum power factor of [Formula: see text]WK[Formula: see text]m[Formula: see text] at 950 K, and the maximum power factor of ANTs is almost twice that of ZNTs.

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