ELECTRICAL BASICS

TRANSFORMERS

HISTORY OF TRANSFORMER :

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FOUNDERS OF TRANSFORMER :

Founders of the transformer Otto Bláthy, Miksa Deri, Károly Zipernowsky of the Austro-Hungarian Empire First designed and used the transformer in both experimental, and commercian systems. Later on Lucien Gaulard,Sebstian Ferranti, and William Stanley perfected the design. But The property of induction was discovered in the 1830's but it wasn't until 1886 that William Stanley, working for Westinghouse built the first refined, commercially used transformer. His work was built upon some rudimentary designs by the Ganz Company in Hungary (ZBD Transformer 1878), and Lucien Gaulard and John Dixon Gibbs in England. Nikola Tesla did not invent the transformer as some dubious sources have claimed. The Europeans mentioned above did the first work in the field, George Westinghouse and Stanley made the transformer cheap to produce, and easy to adjust for final use.

Ottó Bláthy, Miksa Déri, Károly Zipernowsky created the "Z.B.D Transformer"

The first transformer

William Stanley's First Transformer built in 1885

Stanley's first transformer which was used in the electrification of Great Barrington, Massachusetts in 1886

"The first AC power system that used the modern transformer was in the great barring-ton,Massachusetts in 1886 Earlier forms of the transformer were used in Austro-Hungary 1878-1880s and 1882 onward in England.Lucien Gualard (French Man) used his AC system for the revolutionary Lanzo to Turin electrical exposition in 1884(i.e, northern Italy) In 1891 Mastermind Mikhail Dobrovsky designed and demonstrated his 3 phase transformer in the Electro-Technical exposition Frankfurt,Germany.

TRANSFORMER DEVELOPMENT TIME LINES:

1830s - Joseph Henry and Michael Faraday work with electromagnets and discover the property of induction independently on separate continents.

1836 - Rev. Nicholas Callan of Maynooth College, Ireland invents the induction coil
1876 - Pavel Yablochkov uses induction coils in his lighting system

1878 -1883 - The Ganz Company (Budapest, Hungary) uses induction coils in their lighting systems with AC incandescent systems. This is the first appearance and use of the toroidal shaped transformer.

1881 - Charles F. Brush of the Brush Electric Company in Cleveland, Ohio develops his own design of transformer (source: Brush Transformers Inc.)

Definition of Transformer :

A transformer converts an alternating (A/C)currentof a certain voltage to an alternating current of different voltage, without change offrequency by electromagnetic induction A 'step up' transformer receives a low voltage and converts into a higher voltage, and a 'step down' transformer does just the reverse.

A transformer is an electrical device that transfers energy from one circuit to another purely by magnetic coupling. Relative motion of the parts of the transformer is not required for transfer of energy. Transformers are often used to convert between high and low voltages, to change impedance, and to provide electrical isolation between circuits.

Introduction :

The transformer is one of the simplest of electrical devices. Its basic design, materials, and principles have changed little over the last one hundred years, yet transformer designs and materials continue to be improved. Transformers are essential in high voltage power transmission providing an economical means of transmitting power over large distances. The simplicity, reliability, and economy of conversion of voltages by transformers was the principal factor in the selection of alternating current power transmission in the "War of Currents" in the late 1880's. In electronic circuitry, new methods of circuit design have replaced some of the applications of transformers, but electronic technology has also developed new transformer designs and applications.

Transformers come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage microphone to gigawatt units used to interconnect large portions of national power grids, all operating with the same basic principles and with many similarities in their parts.

A transformer has no internal moving parts, and it transfers energy from one circuit to another by electromagnetic induction. External cooling may include heat ex changers, radiators, fans, and oil pumps. Radiators and fans are evident The large horizontal tank at the top is a conservator. Transformers are typically used because a change in voltage is needed.

The following figure shows the basic diagram of a transformer

A simple transformer consists of two electrical conductors called the primary winding and the secondary winding. If a time-varying voltage ${v_P}\,$ is applied to the primary winding of $N_P\,$ turns, a current will flow in it producing a magneto-motive force(MMF). Just as an electromotive force (EMF) drives current around an electric circuit, so MMF drives magnetic flux through a magnetic circuit. The primary MMF produces a varying magnetic flux $\Phi_P\,$ in the core (shaded grey), and induces a back electromotive force (EMF) in opposition to ${v_P}\,$ .

According to the Faraday's law,The voltage induced across the primary winding is proportional to the rate of change of flux :

${v_P} = {N_P} \frac {d \Phi_P}{dt}$

Similarly, the voltage induced across the secondary winding is:

${v_S} = {N_S} \frac {d \Phi_S}{dt}$

With perfect flux coupling, the flux in the secondary winding will be equal to that in the primary winding, and so we can equate $\Phi_P\,$ and $\Phi_S\,$ . It thus follows that:

$\frac{v_P}{v_S}=\frac{N_P}{N_S}.$

Hence,In an ideal transformer the ratio of primary and secondary voltages is equal to the ratio of number of turns in their winding's.The voltage per turn is same in the both winding's.The most common use of the transformer: to convert electrical energy at one voltage to energy at a different voltage by means of winding's with different numbers of turns.

EMF equation

If the flux in the core is sinusoidal, the relationship for either winding between its number of turns, voltage, magnetic flux density and core cross-sectional area is given by the universal emf equation:

$E=4.44 \cdot f \cdot N \cdot a \cdot B$

Where $E\,$ is the sinusoidal root mean square voltage of the winding, $f\,$ is the frequency in hertz, $N\,$ is the number of turns of wire, $a\,$ is the cross-sectional area of the core and $B\,$ is the peak magnetic flux density in Tesla The value 4.44 collects a number of constants required by the system of units.

Types of transformers :

1 . Step-up

The secondary has more turns than the primary

2 . Step-down

The secondary has fewer turns than the primary

3 . Isolating

Intended to transform from one voltage to the same voltage. The two coils have approximately equal numbers of turns, although often there is a slight difference in the number of turns, in order to compensate for losses (otherwise the output voltage would be a little less than, rather than the same as, the input voltage)

4 . Variable

The primary and secondary have an adjustable number of turns which can be selected without reconnecting the transformer.

ELECTRICAL BASICS

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December 20, 2012