What is a Transformer?

What is a Transformer?

A transformer is an electrical device that utilizes the principle of electromagnetic induction to change alternating current (AC) voltage. Its primary components are the primary coil, the secondary coil, and the iron core (or magnetic core). Key functions include: voltage transformation, current transformation, impedance transformation, electrical isolation, and voltage stabilization (as seen in magnetic saturation transformers). Transformers can be categorized by their application into several types, such as distribution transformers, sealed transformers, pad-mounted transformers, dry-type transformers, oil-immersed transformers, single-phase transformers, furnace transformers, and rectifier transformers.

Applications in Daily Life and Industry

Different applications require different voltages. For instance, residential lighting uses 220V, industrial safety lighting uses 36V, and welding machines require adjustable voltage—all made possible by transformers. By adjusting the turns ratio between its primary and secondary coils, a transformer can step down high voltage to the level we need. Conversely, in long-distance power transmission, voltages are stepped up to several thousand or even tens of thousands of volts to minimize line losses—another critical function of transformers.

Impedance Matching

A common application in electronics is impedance matching. To properly connect circuit outputs and inputs, transformers are often used for this purpose. For example, in older audio systems, an output transformer was necessary to match the high impedance of the speaker to the amplifier's output. Thus, transformers are indispensable in both daily life and industrial production.

Key Components and Operating Principle

   Primary Coil (Primary Winding): This is the coil to which the input AC voltage (U1) is applied. The alternating current (I1) flowing through it creates a changing magnetic flux in the iron core.

   Operating Principle: This alternating magnetic flux links both the primary and secondary windings. According to electromagnetic induction, an electromotive force (voltage) is induced in each winding. The magnitude of this induced voltage is proportional to the number of turns in the coil. Therefore, the side with more turns has a higher voltage, and the side with fewer turns has a lower voltage. When the transformer's secondary side is open (no-load condition), the ratio of the primary to secondary voltage equals the ratio of their respective winding turns, achieving voltage transformation.

   Secondary Coil (Secondary Winding): This is the coil in which voltage is induced due to the changing magnetic flux created by the primary current. A changing current in one coil induces a voltage in a nearby, magnetically coupled coil.

   Iron Core (Magnetic Core): The core's function is to concentrate and strengthen the magnetic coupling between the two coils. To minimize energy losses from eddy currents and hysteresis, the core is typically constructed from thin, insulated laminations of silicon steel. The coils themselves are wound with insulated copper or aluminum wire, and there is no direct electrical connection between the primary and secondary windings.

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