Main circuit contacts inspection and maintenance
The number of mechanical operations has a low impact on the life of the main contacts and their overall electrical life. However general information concerning mechanical wear could be of interest.A contact is not necessarily damaged or worn out,just because the surface is rough and discolored. The contacts in the figure
insid e file may look rather inferior but experience has shown that they are better than a new set of contacts. This is because they are ”electrically seated” and make good contact over the entire surface. Based on this it would be completely wrong to change a contact only by judging from the appearance of the surface.
*Interpreting levels of electrical contact wear
*Changing Contacts
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Archive for November, 2008
Main circuit contacts
Sunday, November 30th, 2008Improving Steam Turbine Performance at a Steel Mill
Sunday, November 30th, 2008Gas and steam turbines are common prime movers in power and heating plants. Gas
turbines and steam turbines often suffer from a lack of performance. Possible
reasons are internal wear or deposits on the gas path components, defects in seals
or in effectiveness of cycle heat exchangers all resulting in a decrease of power and efficiency.
Influence from boundary conditions makes it cumbersome to compare guarantee
values with actual performance of the plant.
www.eere.energy.gov
Advanced Foundation Engineering
Sunday, November 30th, 2008geotechnical engineer designs foundations to have the with the limited settlemnt
foundations also is designed structurally by structural engineer settlement and bearing capacity are primary design concerns It is necessary that a foundation is not loaded beyond its bearing capacity or the foundation will “fail”. when water in the ground freezes to form ice lenses Frost heave occurs when flowing water removes supporting soil from around a foundation (like a pier supporting a bridge over a river). Scour occurs
www.reinforcedearth.com
Air cycle refrigeration systems
Sunday, November 30th, 2008Air cycle refrigeration systems belong to the general class of gas cycle
refrigeration systems, in which a gas is used as the working fluid. The gas does not undergo any phase change during the cycle, consequently, all the internal heat transfer processes are sensible heat transfer processes. Gas cycle refrigeration systems find applications in air craft cabin cooling and also in the liquefaction of various gases. In the present chapter gas cycle refrigeration systems based on air are discussed.
www.nptel.iitm.ac.in
A Brief History of Refrigeration
Sunday, November 30th, 2008Although these systems are far less widely used than compression systems, they are the only thermal refrigerating systems that are currently encountering a degree of development. In these systems, instead of using a mechanical compressor to circulate the refrigerant, a pump is used to circulate an absorbent liquid, the quantity of which, in terms of absorbed refrigerant, depends on the temperature and the pressure. The mechanical work is very reduced; however, this system
requires heat.
www.iifiir.org
Fluidized bed boiler
Saturday, November 29th, 2008Circulating fluidized bed (CFB) combustion, with its well-known benefits of fuel flexibility and low emissions, has established itself as a boiler technology suitable for utility-scale power generation. Plant sizes up to 330 MWe are in
operation today, and designs for larger boilers are being developed. Along
with the desire for increased size, there is a desire for increased power plant efficiencies. Almost all of the CFB boilers in operation today, and the bulk of US power stations, operate with natural circulation (drum type boilers). Since increases in size and boiler pressures and temperatures will result in increased power plant efficiency, there is a desire to operate CFB boilers in both larger sizes and at ultra supercritical pressures conditions (steam temperatures typically 1100ºF or higher).
www.fwc.com
Transformer -type Pulse High Voltage Generator
Saturday, November 29th, 2008in-pulse—power technology, a transformer—typeaccelerator is a good candidate for a high—voltagepulse generator suitable for repetitive operations.The well —known double resonance circuit iswidely designed to operate as a transformer typeaccelerator”. The maximum voltage gain ofthe transformer under the double resonancecondition is /L2/L, where L¡ and L2 are a primaryand a secondary inductance of the transformer.Reed51 proposed the greater voltage gain forTesla —transformer accelerator which predictedan 18% increase in voltage gain.
www.lib.nagaokaut.ac.jp
Programmable logic controller
Saturday, November 29th, 2008Control engineering has evolved over time. In the past humans were the main method for controlling a system. More recently electricity has been used for control and early electrical control was based on relays. These relays allow power to be switched on and off without a mechanical switch. It is common to use relays to make simple logical control decisions. The development of low cost computer has brought the most recent revolution, the Programmable Logic Controller (PLC). The advent of the PLC began in the 1970s, and has become the most common choice for manufacturing controls.
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Heat Pipe Selection
Friday, November 28th, 2008Heat pipes are being used very often in particular applications when conventional cooling methods are not suitable. Once the need for heat pipe arises, the most appropriate heat pipe needs to be selected. Often this is not an easy task, and the following needs to be considered.
www.enertron-inc.com
Methanol and Gasoline Production
Tuesday, November 25th, 2008Methanol or methyl alcohol (CH3OH) is a colourless liquid with a boiling point of 65o
C. Methanol will mix with a wide variety of organic liquids as well as with with water and accordingly it is often used as a solvent for domestic and industrial applications. It is most familiar in the home as one of the constituents of methylated spirits. Methanol is the raw material for many chemicals, formaldehyde, dimethyl terephphalate, methylamines and methyl halides, methyl methacrylate, acetic acid, gasoline etc.Methanol and gasoline are produced from Kapuni and Maui natural gas (methane) by Methanex New Zealand Ltd around Waitara and New Plymouth in North Taranaki. Methane is steam reformed to make syngas (hydrogen and carbon monoxide), and this in turn is used to make methanol some of which can be used in methanol to
gasoline (MTG) production. For economic reasons the MTG plant was taken out of production in late 1996, but could be recommissioned if the economic situationwarranted it. In this article the overall layout and production steps at the Methanex plants will be described, followed by sections on the chemistry of methanol and gasoline production.
www.nzic.org.nz