Linear electric generator

In the simplest form of linear electric generator, a sliding magnet moves back and forth through a solenoid - a spool of copper wire. An alternating current is induced in the loops of wire by Faraday's law of induction each time the magnet slides through. This type of generator is used in the Faraday flashlight. Larger linear electricity generators are used in wave power schemes.

Terminology

Rotor from generator at Hoover Dam, United States
The two main parts of a generator or motor can be described in either mechanical or electrical terms:
Mechanical:
• Rotor: The rotating part of an electrical machine
• Stator: The stationary part of an electrical machine
Electrical:
• Armature: The power-producing component of an electrical machine. In a generator, alternator, or dynamo the armature windings generate the electrical current. The armature can be on either the rotor or the stator.
• Field: The magnetic field component of an electrical machine. The magnetic field of the dynamo or alternator can be provided by either electromagnets or permanent magnets mounted on either the rotor or the stator.
Because power transferred into the field circuit is much less than in the armature circuit, AC generators nearly always have the field winding on the rotor and the stator as the armature winding. Only a small amount of field current must be transferred to the moving rotor, using slip rings. Direct current machines necessarily have the commutator on the rotating shaft, so the armature winding is on the rotor of the machine.

MHD generator

A magnetohydrodynamic generator directly extracts electric power from moving hot gases through a magnetic field, without the use of rotating electromagnetic machinery. MHD generators were originally developed because the output of a plasma MHD generator is a flame, well able to heat the boilers of a steam power plant. The first practical design was the AVCO Mk. 25, developed in 1965. The U.S. government funded substantial development, culminating in a 25 MW demonstration plant in 1987. In the Soviet Union from 1972 until the late 1980s, the MHD plant U 25 was in regular commercial operation on the Moscow power system with a rating of 25 MW, the largest MHD plant rating in the world at that time. MHD generators operated as a topping cycle are currently (2007) less efficient than combined-cycle gas turbines

Faraday's disk

In the years of 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 disk', a type of homopolar generator, using a copper disc rotating between the poles of a horseshoe magnet. It produced a small DC voltage.
This design was inefficient due to self-cancelling counterflows of current in regions not under the influence of the magnetic field. While current flow was induced directly underneath the magnet, the current would circulate backwards in regions outside the influence of the magnetic field. This counterflow limits the power output to the pickup wires, and induces waste heating of the copper disc. Later homopolar generators would solve this problem by using an array of magnets arranged around the disc perimeter to maintain a steady field effect in one current-flow direction.
Another disadvantage was that the output voltage was very low, due to the single current path through the magnetic flux. Experimenters found that using multiple turns of wire in a coil could produce higher more useful voltages. Since the output voltage is proportional to the number of turns, generators could be easily designed to produce any desired voltage by varying the number of turns. Wire windings became a basic feature of all subsequent generator designs.
However, recent advances (rare earth magnets) have made possible homo-polar motors with the magnets on the rotor, which should offer many advantages to

genarator Historical developments

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 triboelectric 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 Graaff generator are examples of these machines that have survived

Electrical generator

In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. The reverse conversion of electrical energy into mechanical energy is done by a motor; motors and generators have many similarities. A generator forces electrons in the windings to flow through the external electrical circuit. It is somewhat analogous to a water pump, which creates a flow of water but does not create the water inside. 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.

Auto cad Version history

Official Name Release Date of release Comments


AutoCAD Version 1.0 1 1982, December DWG R1.0 file format introduced.

AutoCAD Version 1.2 2 1983, April DWG R1.2 file format introduced.

AutoCAD Version 1.3 3 1983, August

AutoCAD Version 1.4 4 1983, October DWG R1.4 file format introduced.

AutoCAD Version 2.0 5 1984, October DWG R2.05 file format introduced.

AutoCAD Version 2.1 6 1985, May DWG R2.1 file format introduced.

AutoCAD Version 2.5 7 1986, June DWG R2.5 file format introduced.

AutoCAD Version 2.6 8 1987, April DWG R2.6 file format introduced. Last version to run without a math co-processor.

AutoCAD Release 9 9 1987, September DWG R9 file format introduced.

AutoCAD Release 10 10 1988, October DWG R10 file format introduced.

AutoCAD Release 11 11 1990, October DWG R11 file format introduced.

AutoCAD Release 12 12 1992, June DWG R11/R12 file format introduced. Last release for Apple Macintosh.

AutoCAD Release 13 13 1994, November DWG R13 file format introduced. Last release for Unix, MS-DOS and Windows 3.11.

AutoCAD Release 14 14 1997, February DWG R14 file format introduced.

AutoCAD 2000 15.0 1999, March DWG 2000 file format introduced.

AutoCAD 2000i 15.1 2000, July

AutoCAD 2002 15.2 2001, June

AutoCAD 2004 16.0 2003, March DWG 2004 file format introduced.

AutoCAD 2005 16.1 2004, March

AutoCAD 2006 16.2 2005, March

AutoCAD 2007 17.0 2006, March DWG 2007 file format introduced.

AutoCAD 2008 17.1 2007, March Annotative Objects introduced. First release for the x86-64 versions of Windows XP and Vista.

AutoCAD 2009 17.2 2008, March Revisions to the user interface including the option of a Microsoft Office 2007-like tabbed ribbon.

AutoCAD 2010 18.0 2009, March 24 DWG 2010 file format introduced. Parametrics introduced. Mesh 3D solid modeling introduced. Both 32-bit and 64-bit versions of AutoCAD 2010 and AutoCAD LT 2010 are compatible with and supported under Microsoft Windows 7.

AutoCAD 2011 18.1 2010, March 25 Surface Modeling, Surface Analysis and Object Transparency introduced.