Dynamo

A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter. Today, the simpler alternator dominates large scale power generation, for efficiency, reliability and cost reasons. A dynamo has the disadvantages of a mechanical commutator. Also, converting alternating to direct current using power rectification devices (vacuum tube or more recently solid state) is effective and usually economical.

The word dynamo (from the Greek word dynamis, meaning power) was originally another name for an electrical generator, and still has some regional usage as a replacement for the word generator. The word "dynamo" was coined by Werner von Siemens in 1882. The original "dynamo principle" of W. Siemens meant only the direct current generators which use exclusively the self-excitation (self-induction) principle to generate DC power. The earlier DC generators which used permanent magnets were not considered "dynamo electric machines". The invention of the Dynamo principle (self-induction) was a huge technological leap over the old traditional permanent magnet based DC generators. The discovery of the dynamo principle made the industrial scale electric power generation technically and economically feasible. After the invention of the alternator and that alternating current can be used as a power supply, the word dynamo became associated exclusively with the commutated direct current electric generator, while an AC electrical generator using either slip rings or rotor magnets would become known as an alternator.

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