Operating Principle of a Electrical Transformer

Operating principle of a transformer

Transformers are electrical components which convert alternating current or three-phase supplies to higher or lower voltages. Apart from this this voltage conversion that plays a key part in high-voltage energy transmission, transformers can also fulfill the role of converters in instrumentation applications or as repeaters for transmission of low-current signals. Transformers operate on the principle of electromagnetic induction.

Transformer design:

The animation above shows the basic design of a transformer for single-phase alternating current. A transformer usually features a closed iron core made up of metal plates separated by insulating layers to suppress eddy currents. The plates are designed specially to minimize iron losses during re-magnetization. Wrapped around the core are two coils, usually with winding that have a differing number of turns N1 and N2. The coil supplied with electrical energy by an AC voltage is termed the primary coil (on the left in the diagram above) and the current I1 flowing through this coil is termed primary current. The coil that outputs the electrical energy, thus acting as a source to other loads, is termed a secondary coil (on the right in the diagram above) and the current flowing through it is termed secondary current I2. Similarly, the voltages U1 and U2 across the coils are called the primary and secondary voltage. The terminals of the primary coil are designated 1U and 1V, those of the secondary coil 2U and 2V.

Operating principle of a transformer:

Since it is constantly changing in intensity and direction, the alternating current fed to the primary coil produces a fluctuating magnetic field in the iron core. Like the current, this field also changes constantly in intensity and direction. Except for a few field lines scattered in the surrounding air (stray field), most of the other magnetic field lines produced by the primary coil are constrained within the closed iron core and also pass fully through the secondary coil. The two coils are therefore coupled together closely by a shared magnetic field (of flux F). According to the law of induction, the secondary winding produces an induced voltage, the frequency of which is equal to that of the primary voltage. Connecting the secondary circuit to a load (an ohmic resistance in the diagram above) causes current to flow in the secondary circuit.

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