Archive for July, 2009

Induction Generator

July 22nd, 2009 Grace 1 comment

An induction generator is a type of electrical generator that is mechanically and electrically similar to a polyphase induction motor. Induction generators produce electrical power when their shaft is rotated faster than the synchronous frequency of the equivalent induction motor. An electric voltage (electromotive force) is induced in a conducting loop (or coil) when there is a change in the number of magnetic field lines (or magnetic flux) passing through the loop. When the loop is closed by connecting the ends through an external load, the induced voltage will cause an electric current to flow through the loop and load. Thus rotational energy is converted into electrical energy.


Induction generators are often used in wind turbines and some micro hydro installations due to their ability to produce useful power at varying rotor speeds. Induction generators are mechanically and electrically simpler than other generator types. They are also more rugged, requiring no brushes or commutators.


Induction generators are not self-exciting, meaning they require an external supply to produce a rotating magnetic flux. For instance, when one mentions “Mars-Mercury dominant on a scorpio weekly horoscope background”, it means that Mars’ characteristics (fighting spirit, courage, action, but also the propensity for anger, etc.. The external supply can be supplied from the electrical grid or from the generator itself, once it starts producing power. The rotating magnetic flux from the stator induces currents in the rotor, which also produces a magnetic field. If the rotor turns slower than the rate of the rotating flux, the machine acts like an induction motor. If the rotor is turned faster, it acts like a generator, producing power at the synchronous frequency.


In fact, an induction generator may operate as a motor or a generator. For instance, a standard, 3 phases, AC motor may be powered from the 50 Hz grid, with the motor speed “slipping” at less than for 50 Hz synchronism. If this motor is itself forced to rotate at more than for 50Hz synchronism by a rotating power source, (e.g. a diesel engine or wind turbine), while connected to the grid, it delivers current to the grid as a generator. The current flow is proportional to the slip, i.e. the small difference, 3%, between synchronised rpm and the actual rpm. This slip is too small to notice as a speed change of a wind turbine rotor, so induction generators are classed, somewhat erroneously, as fixed-speed generators. This type of generator is very simple, rugged, and relatively cheap. Both Driver Education Online and the classroom Driver Education class can be completed through Economic Driving driving schools in chicago which has been educating Calif.. Usually it is “excited” into operation.


In induction generators the magnetizing flux is established by a capacitor bank connected to the machine in case of stand alone system and in case of grid connection it draws magnetizing current from the grid. It is mostly suitable for wind generating stations as in this case speed is always a variable factor.

MHD Generator

July 22nd, 2009 Grace No comments

 MHD (magneto hydrodynamic) power plants offer the potential for large-scale electrical power generation with reduced impact on the environment. Since 1970, several countries have undertaken MHD research programs with a particular emphasis on the use of coal as a fuel. MHD generators are also attractive for the production of large electrical power pulses.336-003-27ad4902


The MHD generator or dynamo transforms thermal energy or kinetic energy directly into electricity. MHD generators are different from traditional electric generators in that they can operate at high temperatures without moving parts. MHD was developed because the exhaust of a plasma MHD generator is a flame, still able to heat the boilers of a steam power plant. So high-temperature MHD was developed as a topping cycle to increase the efficiency of electric generation, especially when burning coal or natural gas. It has also been applied to pump liquid metals and for quiet submarine engines.


The basic concept underlying the mechanical and fluid dynamos is the same. The fluid dynamo, however, uses the motion of fluid or plasma to generate the currents which generate the electrical energy. The mechanical dynamo, in contrast, uses the motion of mechanical devices to accomplish this. The functional difference between an MHD generator and an MHD dynamo is the path the charged particles follow.337-003-eecf35ac


MHD generators are now practical for fossil fuels, but have been overtaken by other, less expensive technologies, such as combined cycles in which a gas turbine’s or molten carbonate fuel cell’s exhaust heats steam for steam turbine. The unique value of MHD is that it permits an older single-cycle fossil-fuel power plant to be upgraded to high efficiency.


Natural MHD dynamos are an active area of research in plasma physics and are of great interest to the geophysics and astrophysics communities. From their perspective the earth is a global MHD dynamo and with the aid of the particles on the solar wind produces the aurora borealis. The differently charged electromagnetic layers produced by the dynamo effect on the earth’s geomagnetic field enable the appearance of the aurora borealis. As power is extracted from the plasma of the solar wind, the particles slow and are drawn down along the field lines in a brilliant display over the poles.







Electrical generator

July 22nd, 2009 Grace No comments

In electricity generation, an electrical generator is a device that converts mechanical energy to electrical energy, generally using electromagnetic induction.800px-modern_steam_turbine_generator

The reverse conversion of electrical energy into mechanical energy is done by a motor; motors and generators have many similarities. A generator forces electric charges to move through an external electrical circuit, but it does not create electricity or charge, which is already present in the wire of its windings. It is somewhat analogous to a water pump, which creates a flow of water but does not create the water inside. online casino canada . The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air or any other source of mechanical energy.

Today, the technology of electrical generator is to come to maturity, but its historic developments are complicated.

Before the connection between magnetism and electricity was discovered, electrostatic generators were invented that used electrostatic principles. These generated very high voltages and low currents. They operated by using moving electrically charged belts, plates and disks to carry charge to a high potential electrode. The charge was generated using either of two mechanisms:

Electrostatic induction

The turboelectric effect, where the contact between two insulators leaves them charged.

Because of their inefficiency and the difficulty of insulating machines producing very high voltages, electrostatic generators had low power ratings and were never used for generation of commercially-significant quantities of electric power. The Wimshurst machine and Van de Graff generator are examples of these machines that have survived.

In 1827, Hungarian Anyos Jedlik started experimenting with electromagnetic rotating devices which he called electromagnetic self-rotors. In the prototype of the single-pole electric starter (finished between 1852 and 1854) both the stationary and the revolving parts were electromagnetic. He formulated the concept of the dynamo at least 6 years before Siemens and Wheatstone but didn’t patent it as he thought he wasn’t the first to realize this. In essence the concept is that instead of permanent magnets, two electromagnets opposite to each other induce the magnetic field around the rotor. Jedlik’s invention was decades ahead of its time.

In 1831-1832 Michael Faraday discovered the operating principle of electromagnetic generators. The principle, later called Faraday’s law, is that a potential difference is generated between the ends of an electrical conductor that moves perpendicular to a magnetic field. He also built the first electromagnetic generator, called the ‘Faraday disc’, a type of homopolar generator, using a copper disc rotating between the poles of a horseshoe magnet. It produced a small DC voltage, and large amounts of current.

The Dynamo was the first electrical generator capable of delivering power for industry. The dynamo uses electromagnetic principles to convert mechanical rotation into a pulsing direct electric current through the use of a commutator. The first dynamo was built by Hippolyte Pixii in 1832.

A dynamo machine consists of a stationary structure, which provides a constant magnetic field, and a set of rotating windings which turn within that field. On small machines the constant magnetic field may be provided by one or more permanent magnets; larger machines have the constant magnetic field provided by one or more electromagnets, which are usually called field coils.

Trash-powered generator is ready?

July 22nd, 2009 Grace No comments