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Post on 13-Jul-2015
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A transformer is a device that transfers electrical energy from one circuit to another.
It is done by changing current in the first circuit (primary) creating a magnetic field that induces voltage in the second voltage (secondary).
1831 transformer principle was demonstrated by Michael Faraday1836 first widely used transformer (induction coil) was invented by Nicholas Callan1830s-1870s efforts were made to build better induction coils1880s efficient induction coils were introduced1876 lighting system based on induction coils was invented by Pavel Yablochkov
1885 the commmercial transformer was built by William Stanley1889 first three-phase transformer was developed by Russian engineer Mikhail Dolivo-Dobrovolsky. 1891 the Tesla coil, a resonant transformer for generating very high voltages at high frequency was invented by Nikola Tesla.Present some transformers are used in many electronic devices
Autotransformerhas only a single winding with two end terminals, plus a third at an intermediate tap point. The primary voltage is applied across two of the terminals, and the secondary voltage taken from one of these and the third terminal. The primary and secondary circuits therefore have a number of windings turns in common.
Polyphase Transformerthree individual single-phase transformers incorporated as a single three-phase transformer and is used for three-phase supplies. In this case, the magnetic circuits are connected together, the core thus containing a three-phase flow of flux.
Leakage Transformersalso called a stray-field transformer, has a significantly higher leakage inductance than other transformer. Leakage transformers are used for arc welding and high voltage discharge lamps. It acts then both as a voltage transformer and as a magnetic ballast.
Resonant Transformera kind of the leakage transformer that uses the leakage inductance of its secondary windings in combination with external capacitors, to create one or more resonant circuits that can generate very high voltages.
Instrument Transformersis a measurement device designed to provide a current in its secondary coil proportional to the current flowing in its primary. They are designed to present negligible load to the supply being measured and to have a precise voltage ratio to accurately step down high voltages.
Transformers can be classified in different ways:
By power level: from a fraction of a volt-ampere (VA) to over a thousand MVA; By frequency range: power-, audio-, or radio frequency; By voltage class: from a few volts to hundreds of kilovolts; By cooling type: air cooled, oil filled, fan cooled, or water cooled; By application function: such as power supply, impedance matching, output voltage and current stabilizer, or circuit isolation; By end purpose: distribution, rectifier, arc furnace, amplifier output; By winding turns ratio: step-up, step-down, isolating (near equal ratio), variable.
used to increase voltage before transmitting electrical energy over long distances through wires.enable economic transmission of power over long distances.used extensively in electronic products to step down the supply voltage to a level suitable for the low voltage circuits they contain. electrically isolates the end user from contact with the supply voltage