Electrical Generator Developments Faraday Dynamo Gramme Dynamo

Before the connection between magnetism and electricity was discovered, generators used electrostatic principles. The Wimshurst machine used electrostatic induction or "influence". The Van de Graaff generator uses either 1) a charge transfer from a high-voltage electrode or 2) the triboelectric effect to separate electric charges using the friction between insulators. Electrostatic generators are inefficient and are useful only for scientific experiments requiring high voltages.

1.1 Faraday

In 1831- 1832 Michael Faraday discovered that a potential difference is generated between the ends of an electrical conductor that moves perpendicular to a magnetic field. He built the first electromagnetic generator based on this effect, using a copper disc rotating between the poles of a horseshoe magnetThis article is about magnetized material. Magnet is also the name of a commune in the Allier departement, in France A magnet is an object that has a magnetic field. A so-called permanent magnet is made of a ferromagnetic material. Such materials consist. It produced a small direct currentDirect current DC or continuous current ) is the continuous flow of electricity through a conductor such as a wire from high to low potential. In direct current, the electric charges flow always in the same direction, which distinguishes it from alternati.

1.2 Dynamo

The dynamo was the first electrical generator capable of delivering power for industry, and is still the most important generator in use in the 21st century20th century 21st century 22nd century other centuries) Definition In calendars based on the Christian Era or Common Era, such as the Gregorian calendar, the 21st century is the current century, as of this writing, lasting from 2001- 2100. The 21st centur. The dynamo uses electromagneticElectromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. The electric field is produced by stationary electric charges, and gives rise to the electric force, t principles to convert mechanical rotation into an alternating electric currentIn electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. Conventional current was defined early in the history of electrical science as a flow of positive charge, although we now know that, i.

The first dynamo based on Faraday's principles was built in 1832 by Hippolyte Pixii , a French instrument maker. It used a permanent magnet which was rotated by a crank. The spinning magnet was positioned so that its north and south poles passed by a piece of iron wrapped with wire. Pixii found that the spinning magnet produced a pulse of current in the wire each time a pole passed the coil. Furthermore, the north and south poles of the magnet induced currents in opposite directions. By adding a commutatorA commutator is an electrical switch that periodically reverses the current in an electric motor or electrical generator. It enables a motor to run on, and a generator to produce, a direct current instead of an alternating current. It typically consists o, Pixii was able to convert the alternating current to direct current.

1.3 Gramme dynamo

However, both of these designs suffered from a similar problem: they induced "spikes" of current followed by none at all. Antonio PacinottiAntonio Pacinotti (June 17 1841 March 24 1912) was a Professor of Physics at the University of Pisa. He is best known for inventing an improved form of direct-current electrical generator, or dynamo, which he described in a paper published in Il Nuovo Cim, an Italian scientist, fixed this by replacing the spinning coil with a toroidal one, which he created by wrapping an iron ring. This meant that some part of the coil was continually passing by the magnets, smoothing out the current. Zénobe Gramme reinvented this design a few years later when designing the first commercial power plants, in Paris in the 1870s. His design is now known as the Gramme dynamo. Various versions and improvements have been made since then, but the basic concept of a spinning endless loop of wire remains at the heart of all modern dynamos.

2 Concepts

It is important to understand that the generator creates an electric current, but does not create electric charge, which is already present in the conductive wire of its windings. It is somewhat analogous to a water pump, which creates a flow of water but does not create the water itself.

Other types of electrical generator exist, based on other electrical phenomena such as piezoelectricity, and magnetohydrodynamics. The construction of a dynamo is similar to that of an electric motor, and all common types of dynamos could work as motors. Also, all common types of electric motors could work as generators.

The Generator rotor is turned by a device termed a Prime Mover, often a Diesel engine, Steam turbine , Water turbine or Gas turbine coupled to the rotor shaft.

3 Equivalent circuit

The equivalent circuit of a generator and load is shown in the diagram on the right. To determine the generator's and parameters, follow this procedure: -

Before starting the generator, measure the resistance across its terminals using an ohmmeter. This is its DC internal resistance .
Start the generator. Before connecting the load , measure the voltage across the generator's terminals. This is the open-circuit voltage .
Connect the load as shown in the diagram, and measure the voltage across it with the generator running. This is the on-load voltage .
Measure the load resistance , if you don't already know it.
Calculate the generator's AC internal resistance from the following formula:

Note 1: The AC internal resistance of the generator when running is generally slightly higher than its DC resistance when idle. The above procedure allows you to measure both values. For rough calculations, you can omit the measurement of and assume that and are equal.

Note 2: If the generator is an AC type (not a dynamo), use an AC voltmeter for the voltage measurements.

4 See also

Distributed generation

Electrical engineering

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1 Developments