L#4-Transformers

L#4-Transformers - Transformers Masoud Fathizadeh, PhD, PE...

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Transformers Masoud Fathizadeh, PhD, PE Department of Engineering Technology Purdue Calumet Hammond, Indiana 46323
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Transformers
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Some history The second generation of power distribution systems (what we are still using) was proposed by Tesla few years later. His idea was to generate AC power of any convenient voltage, step up the voltage for transmission (higher voltage implies lower current and, thus, lower losses), transmit AC power with small losses, and finally step down its voltage for consumption. Since power loss is proportional to the square of the current transmitted, raising the voltage, say, by the factor of 10 would decrease the current by the same factor (to deliver the same amount of energy) and, therefore, reduce losses by factor of 100. Historically , the first electrical power distribution system developed by Edison in 1880s was transmitting DC . It was designed for low voltages (safety and difficulties in voltage conversion); therefore, high currents were needed to be generated and transmitted to deliver necessary power. This system suffered significant energy losses ! The step up and step down voltage conversion was based on the use of transformers .
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Preliminary considerations A transformer is a device that converts one AC voltage to another AC voltage at the same frequency. It consists of one or more coil(s) of wire wrapped around a common ferromagnetic core. These coils are usually not connected electrically together. However, they are connected through the common magnetic flux confined to the core. Assuming that the transformer has at least two windings, one of them ( primary ) is connected to a source of AC power; the other ( secondary ) is connected to the loads. The invention of a transformer can be attributed to Faraday, who in 1831 used its principle to demonstrate electromagnetic induction foreseen no practical applications of his demonstration. Russian engineer Yablochkov in 1876 invented a lighting system based on a set of induction coils, which acted as a transformer.
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More history Gaulard and Gibbs first exhibited a device with an open iron core called a 'secondary generator' in London in 1882 and then sold the idea to a company Westinghouse. They also exhibited their invention in Turin in 1884, where it was adopted for an electric lighting system. In 1885, William Stanley, an engineer for Westinghouse, built the first commercial transformer after George Westinghouse had bought Gaulard and Gibbs' patents. The core was made from interlocking E-shaped iron plates. This design was first used commercially in 1886. Hungarian engineers Zipernowsky, Bláthy and Déri created the efficient "ZBD" closed- core model in 1885 based on the design by Gaulard and Gibbs. Their patent application made the first use of the word "transformer". Another Russian engineer Dolivo-Dobrovolsky developed the first three-phase transformer in 1889.
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L#4-Transformers - Transformers Masoud Fathizadeh, PhD, PE...

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