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Electric generator

Electric generators are devices for producing electrical energy from another form of energy. In contrast, a device that consumes electrical energy is called an electrical receiver.

Voltage generator

It enables an almost constant voltage to be supplied without loss of load. It is a theoretical model which makes it possible to overcome the internal resistance of the generator. (Analogue for current generators)

Voltage generator

Symbol of a voltage generator in a circuit

Electrochemical generator

Electrochemical accumulators are direct current generators, rechargeable, used in electrotechnical and portable electronic applications.

Electrostatic machine

DC rotary machine

DC rotary machine

A direct current generator popularly called a dynamo is, like many electric generators, a rotating machine. It was invented by Zénobe Gramme.


This machine works as a generator but is reversible as a motor. The constituent details of the machine are detailed in the article direct current machine.


This type of generator being reversible, it easily becomes an electric motor, which implies that when stopping the dynamo must be disconnected from its load if the latter can provide it with a current in return: accumulator battery, other dynamo.

DC machine: The dynamoabbas

Alternating Current Rotary Machine

The discovery in 1832 by Faraday of the phenomena of electromagnetic induction allowed him to consider producing alternating electric voltages and currents using magnets. Pixii, on the instructions of Ampère built the same year a first machine which was then perfected (1833 – 1834) by Sexton and Clarke. An alternator is a rotating machine that converts the mechanical energy supplied by an engine (turbine, diesel, wind turbine, etc.) into alternating current electrical energy.

More than 95% of electrical energy is produced by synchronous alternators: electromechanical machines providing voltages of frequencies proportional to their speed of rotation. These machines are less expensive and have a better efficiency than direct current machines (dynamos) which deliver continuous voltages (95% instead of 85%).

Asynchronous machines in hypersynchronous operation (rotation frequency greater than the synchronous frequency) also supply energy to the AC network to which they are connected. They are used more and more as generators thanks to recent progress in power electronics.

Principle of synchronous alternator

the synchronous alternator

Exploded view generator

As the machines are all reversible, reference is made to the synchronous machine article.

This machine consists of a rotor (rotating part) and a stator (fixed part).

Different types of alternators

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