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This electromagnetic induction phenomenon is the basis of transformer action and, in accordance with Lenz's law, the secondary current so produced creates a flux equal and opposite to that produced by the primary winding. This varying flux at the secondary winding induces a varying electromotive force or voltage in the secondary winding. Ideal transformer and induction law Ī varying current in the transformer's primary winding creates a varying magnetic flux in the transformer core, which is also encircled by the secondary winding. Ideal transformer connected with source V P on primary and load impedance Z L on secondary, where 0 < Z L < ∞. Perfect coupling implies infinitely high core magnetic permeability and winding inductance and zero net magnetomotive force (i.e. Where Z L is the apparent load or driving point impedance of the primary circuit, the superscript ′ ' denoting referred to the primary.Īn ideal transformer is linear, lossless and perfectly coupled. Transformers range in size from RF transformers less than a cubic centimeter in volume, to units weighing hundreds of tons used to interconnect the power grid. A wide range of transformer designs is encountered in electronic and electric power applications.

Since the invention of the first constant-potential transformer in 1885, transformers have become essential for the transmission, distribution, and utilization of alternating current electric power. Transformers can also be used to provide galvanic isolation between circuits as well as to couple stages of signal-processing circuits. Transformers are used to change AC voltage levels, such transformers being termed step-up or step-down type to increase or decrease voltage level, respectively.

Faraday's law of induction, discovered in 1831, describes the induced voltage effect in any coil due to a changing magnetic flux encircled by the coil. Electrical energy can be transferred between separate coils without a metallic (conductive) connection between the two circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer's core, which induces a varying electromotive force (EMF) across any other coils wound around the same core. A basic transformer consisting of two coils of copper wire wrapped around a magnetic coreĪ transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. For other uses, see Transformer (disambiguation). This article is about the electrical device.