- The earliest transformer was invented in 1836 by Nicholas Callan. It consisted of air core induction coils with a varying number of turns. The goal of these devices were to coax higher voltages from battery sources. After varying degrees of development, in 1885, the first closed core devices were mutually developed by Blathy, Deri and Zipernowsky. Instead of being in the open air like their former incarnations, these transformers had the coils wrapped around the central core, which operated to keep the magnetic field just about completely within the core. As a result, voltages were better regulated, and transformers finally started their quick journey of entering industry.
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The operating principles of a transformer rely upon the relationship between electrical current and magnetic fields. This relationship is based on change: when the current changes (due to an alternating current source), a magnetic field is created, and when the field changes, a current is made. These two linked quantities can be labeled as field B and current I. The relationship between the two has the magnetic field B directly proportional to the current I, as well as the number of turns, or layers, in the coil.
A transformer works by exploiting both the current-generating-field phenomenon and the field-generating-current phenomenon. The first current I1 creates the field B. The field B then creates the current I2 in the secondary coil. If the primary and secondary coils are identical, the currents will equal each other. If, however, the secondary coil has twice as many turns, then the field B will generate only half the current.
Throughout this process, power is conserved (ideally). Since the power is the product of voltage V and current I, half the current means twice the voltage. This is the effect being exploited. Three times the number of turns means that V2 = 3V1. Half the number of turns results in half the voltage, and so on. - No real system conserves power completely, and the electrical transformer is no different. It has a number of sources of power loss that can affect the current and/or the voltage in the secondary coil. Most of these are due to the generation of heat, which results from magnetic fields being where they should not be. Magnetic fields can have lose energy to eddy currents and have small losses due to the expansion and contraction of magnetic material. Currents can also see losses in the form of resistance in the coils and the tiny mechanical vibrations that occur in the coils as the magnetic field exerts a force on the charged lines. In any transformer design, losses are a necessary part of recipe and need to be compensated for.
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There are quite a few transformer designs that are in use today, each of which possesses benefits that suits its intended purpose. Instrument transformers are designed for the purpose of measuring the current and/or voltage in a given power line or circuit, being especially tailored to maximize accuracy. Pulse transformers are made to work with the rectangular pulses that make up the bulk of digital logic circuits. Transformers work with alternating current, and when the current alternates at radio frequencies, RF transformers fall into need, as currents in the RF regime pose their own problems.
Transformers also come in a variety of sizes, ranging from the size of a marble to the size of a room, all depending on the power loads and other specifications. One of the best things about transformers is the ease at which a basic transformer can be made, when given wire and a black core. While maybe not as power efficient as other transformers, home-made transformers give complete control to the builder. - Transformers are in just about everything that requires power. In suburban neighborhoods, large metal boxes on the side of the road that are a uniform solid color, get warm and have a slight humming sound are transformers. Transformers are on electrical poles and power substations, since it is more efficient to transmit power at a higher voltage. Transformers have plenty of uses in audio equipment, microphones and speakers. Any little black box that you plug your electronics into the wall with will contain transformers that perform a large portion of the work in dropping the wall voltage of 110 down to 12 or 15 volts. There are many applications of transformers and many solutions that use them.
