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  1. Transformer - Wikipedia › wiki › Transformer

    In 1891, Nikola Tesla invented the Tesla coil, an air-cored, dual-tuned resonant transformer for producing very high voltages at high frequency. [77] Audio frequency transformers (" repeating coils ") were used by early experimenters in the development of the telephone .

  2. Transformers: Age of Extinction - Wikipedia › wiki › Transformers_4

    From Wikipedia, the free encyclopedia. Transformers: Age of Extinction is a 2014 American science fiction action film based on the Transformers toy line. It is the fourth installment of the live-action Transformers film series and the sequel to Dark of the Moon (2011), taking place five years after its events.

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    Why are Transformers more compact at higher frequencies?

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  4. Very high frequency - Wikipedia › wiki › Very_high_frequency

    Very high frequency ( VHF) is the ITU designation for the range of radio frequency electromagnetic waves ( radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF).

    • 10 to 1 m
    • 30 MHz to 300 MHz
  5. Transformer types - Wikipedia › wiki › Transformer_types

    A Flyback transformer is a high-voltage, high-frequency transformer used in plasma balls and with cathode-ray tubes (CRTs). It provides the high (often several kV) anode DC voltage required for operation of CRTs. Variations in anode voltage supplied by the flyback can result in distortions in the image displayed by the CRT.

  6. High frequency - Wikipedia › wiki › High_frequency

    High frequency ( HF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred meters). Frequencies immediately below HF are denoted medium frequency (MF), while the next band of higher frequencies is known as the very high frequency (VHF) band.

    • 100 to 10 m
    • 3 to 30 MHz
  7. Transformer wiki | TheReaderWiki › en › Transformer
    • Principles
    • Construction
    • Classification Parameters
    • Applications
    • History

    Ideal transformer

    An ideal transformer is a theoretical linear transformer that is lossless and perfectly coupled. Perfect coupling implies infinitely high core magnetic permeability and winding inductances and zero net magnetomotive force (i.e. ipnp - isns = 0).[c] A varying current in the transformer's primary winding attempts to create a varying magnetic flux in the transformer core, which is also encircled by the secondary winding. This varying flux at the secondary winding induces a varying electromotive...

    Real transformer

    The ideal transformer model neglects the following basic linear aspects of real transformers: (a) Core losses, collectively called magnetizing current losses, consisting of 1. Hysteresislosses due to nonlinear magnetic effects in the transformer core, and 2. Eddy currentlosses due to joule heating in the core that are proportional to the square of the transformer's applied voltage. (b) Unlike the ideal model, the windings in a real transformer have non-zero resistances and inductances associa...

    Transformer EMF equation

    If the flux in the core is purely sinusoidal, the relationship for either winding between its rms voltage Erms of the winding, and the supply frequency f, number of turns N, core cross-sectional area a in m2 and peak magnetic flux density Bpeak in Wb/m2or T (tesla) is given by the universal EMF equation: 1. E rms = 2 π f N a B peak 2 ≈ 4.44 f N a B peak {\\displaystyle E_{\\text{rms}}={\\frac {2\\pi fNaB_{\\text{peak}}}{\\sqrt {2}}}\\approx 4.44fNaB_{\\text{peak}}}


    Core form = core type; shell form = shell type Closed-core transformers are constructed in 'core form' or 'shell form'. When windings surround the core, the transformer is core form; when windings are surrounded by the core, the transformer is shell form. Shell form design may be more prevalent than core form design for distribution transformer applications due to the relative ease in stacking the core around winding coils. Core form design tends to, as a general rule, be more economical, and...


    The electrical conductor used for the windings depends upon the application, but in all cases the individual turns must be electrically insulated from each other to ensure that the current travels throughout every turn. For small transformers, in which currents are low and the potential difference between adjacent turns is small, the coils are often wound from enamelled magnet wire. Larger power transformers may be wound with copper rectangular strip conductors insulated by oil-impregnated pa...


    It is a rule of thumb that the life expectancy of electrical insulation is halved for about every 7 °C to 10 °C increase in operating temperature (an instance of the application of the Arrhenius equation). Small dry-type and liquid-immersed transformers are often self-cooled by natural convection and radiation heat dissipation. As power ratings increase, transformers are often cooled by forced-air cooling, forced-oil cooling, water-cooling, or combinations of these. Large transformers are fil...

    Transformers can be classified in many ways, such as the following: 1. Power rating: From a fraction of a volt-ampere (VA) to over a thousand MVA. 2. Duty of a transformer: Continuous, short-time, intermittent, periodic, varying. 3. Frequency range: Power-frequency, audio-frequency, or radio-frequency. 4. Voltage class: From a few volts to hundreds of kilovolts. 5. Cooling type: Dry or liquid-immersed; self-cooled, forced air-cooled;forced oil-cooled, water-cooled. 6. Application: power supply, impedance matching, output voltage and current stabilizer, pulse, circuit isolation, power distribution, rectifier, arc furnace, amplifier output, etc.. 7. Basic magnetic form: Core form, shell form, concentric, sandwich. 8. Constant-potential transformer descriptor: Step-up, step-down, isolation. 9. General winding configuration: By IEC vector group, two-winding combinations of the phase designations delta, wye or star, and zigzag; autotransformer, Scott-T 10. Rectifier phase-shift winding c...

    Various specific electrical application designs require a variety of transformer types. Although they all share the basic characteristic transformer principles, they are customized in construction or electrical properties for certain installation requirements or circuit conditions. In electric power transmission, transformers allow transmission of electric power at high voltages, which reduces the loss due to heating of the wires. This allows generating plants to be located economically at a distance from electrical consumers.All but a tiny fraction of the world's electrical power has passed through a series of transformers by the time it reaches the consumer. In many electronic devices, a transformer is used to convert voltage from the distribution wiring to convenient values for the circuit requirements, either directly at the power line frequency or through a switch mode power supply. Signal and audio transformers are used to couple stages of amplifiers and to match devices such...

    Discovery of induction

    Electromagnetic induction, the principle of the operation of the transformer, was discovered independently by Michael Faraday in 1831 and Joseph Henry in 1832. Only Faraday furthered his experiments to the point of working out the equation describing the relationship between EMF and magnetic flux now known as Faraday's law of induction: 1. | E | = | d Φ B d t | , {\\displaystyle |{\\mathcal {E}}|=\\left|{{\\mathrm {d} \\Phi _{\\text{B}}} \\over \\mathrm {d} t}\\right|,} where | E | {\\displaystyle |{\\m...

    Induction coils

    The first type of transformer to see wide use was the induction coil, invented by Rev. Nicholas Callan of Maynooth College, Ireland in 1836. He was one of the first researchers to realize the more turns the secondary winding has in relation to the primary winding, the larger the induced secondary EMF will be. Induction coils evolved from scientists' and inventors' efforts to get higher voltages from batteries. Since batteries produce direct current (DC) rather than AC, induction coils relied...

    First alternating current transformers

    By the 1870s, efficient generators producing alternating current (AC) were available, and it was found AC could power an induction coil directly, without an interrupter. In 1876, Russian engineer Pavel Yablochkov invented a lighting system based on a set of induction coils where the primary windings were connected to a source of AC. The secondary windings could be connected to several 'electric candles'(arc lamps) of his own design. The coils Yablochkov employed functioned essentially as tran...

  8. Transformer | Wikitronics | Fandom › wiki › Transformer
    • History
    • Basic Principles
    • Practical Considerations
    • Transformer Types and Uses
    • Construction
    • External Links

    Michael Faraday built the first transformer in 1831, although he used it only to demonstrate the principle of electromagnetic induction and did not foresee its practical uses. Lucien Gaulard and John Dixon Gibbs, who first exhibited a device called a 'secondary generator' in London in 1882 and then sold the idea to American company Westinghouse. This may have been the first practical power transformer. They also exhibited the invention in Turin in 1884, where it was adopted for an electric lighting system. Their early devices used an open iron core, which was soon abandoned in favour of a more efficient circular core with a closed magnetic path. Russian engineer Pavel Yablochkov in 1876 invented a lighting system based on a set of induction coils, where primary windings were connected to a source of alternating current and secondary windings could be connected to several "electric candles". As the patent said, such a system "allows to provide separate supply to several lighting fixt...

    Coupling by mutual induction

    The principles of the transformer are illustrated by consideration of a hypothetical ideal transformer consisting of two windings of zero resistance around a core of negligible reluctance. A voltage applied to the primary winding causes a current, which develops a magnetomotive force (MMF) in the core. The current required to create the MMF is termed the magnetising current; in the ideal transformer it is considered to be negligible. The MMF drives flux around the magnetic circuitof the core....

    Under load

    If a load impedance is connected to the secondary winding, a current will flow in the secondary circuit so created. The current develops an MMF over the secondary winding in opposition to that of the primary winding, so acting to cancel the flux in the core. The now decreased flux reduces the primary EMF, causing current in the primary circuit to increase to exactly offset the effect of the secondary MMF, and returning the flux to its former value. The core flux thus remains the same regardle...

    Circuit symbols

    Standard symbols

    Effect of frequency

    The time-derivative term in Faraday's Law implies that the flux in the core is the integral of the applied voltage. An ideal transformer would, at least hypothetically, work under direct-current excitation, with the core flux increasing linearly with time. In practice, the flux would rise very rapidly to the point where magnetic saturationof the core occurred and the transformer would cease to function as such. All practical transformers must therefore operate under alternating (or pulsed) cu...

    Energy losses

    An ideal transformer would have no energy losses, and would therefore be 100% efficient. Despite the transformer being amongst the most efficient of electrical machines, with experimental models using superconducting windings achieving efficiencies of 99.85%, energy is dissipated in the windings, core, and surrounding structures. Larger transformers are generally more efficient, and those rated for electricity distribution usually perform better than 95%.A small transformer such as a plug-in...

    A variety of specialised transformer designs has been created to fulfil certain engineering applications. The numerous applications to which transformers are adapted lead them to be classified in many ways: 1. By power level: from a fraction of a volt-ampere(VA) to over a thousand MVA; 2. By frequency range: power-, audio- or radio frequency; 3. By voltage class: from a few volts to hundreds of kilovolts; 4. By cooling type: air cooled, oil filled, fan cooled, or water cooled; 5. By application function: such as power supply, impedance matching or circuit isolation; 6. By end purpose: distribution, rectifier, arc furnace, amplifier output; 7. By winding turns ratio: step-up, step-down, isolating (near equal ratio), variable.


    The wire of the adjacent turns in a coil, and in the different windings, must be electrically insulated from each other. The wire used is generally magnet wire. Magnet wire is a copper wire with a coating of varnish or some other synthetic coating. Transformers for years have used Formvarwire, which is a varnished type of magnet wire. The conducting material used for the winding depends upon the application. Small power and signal transformers are wound with solid copper wire, insulated usual...

    Winding insulation

    The turns of the windings must be insulated from each other to ensure that the current travels through the entire winding. The potential difference between adjacent turns is usually small, so that enamel insulation may suffice for small power transformers. Supplemental sheet or tape insulation is usually employed between winding layers in larger transformers. The transformer may also be immersed in transformer oil that provides further insulation. Although the oil is primarily used to cool th...


    Where transformers are intended for minimum electrostatic coupling between primary and secondary circuits, an electrostatic shield can be placed between windings to reduce the capacitance between primary and secondary windings. The shield may be a single layer of metal foil, insulated where it overlaps to prevent it acting as a shorted turn, or a single layer winding between primary and secondary. The shield is connected to earth ground. Transformers may also be enclosed by magnetic shields,...

    Inside Transformersfrom Denver University
    Understanding Transformers: Characteristics and Limitationsfrom Conformity Magazine
    DMOZ: Business: Electronics and Electrical: Substation and TransmissionTransformers for the Utility sector
  9. Transformer | Engineering | Fandom › wiki › Transformer
    • Basic Principles
    • Invention
    • Construction
    • Transformer Designs
    • Uses of Transformers
    • See Also

    Flux coupling

    A simple single phase transformer consists of two electrical conductors called the primary winding and the secondary winding. The primary is fed with a varying (alternating or pulsed continuous) electric current which creates a varying magnetic field around the conductor. According to the principle of mutual inductance, the secondary, which is placed in this varying magnetic field, will develop an electromotive force or EMF. If the ends of the secondary are connected together to form an elect...

    Electrical laws

    Consider the following two laws: 1. According to the law of conservation of energy, the powerdelivered by a transformer cannot exceed the power fed into it. 2. The power dissipated in a load at any instant is equal to the product of the voltage across it and the (in phase) current passing through it (see also Ohm's law). It follows from the above two laws that a transformer is not an amplifier. If the transformer is used to change power from one voltage to another, the magnitudes of the curre...

    Those credited with the invention of the transformer include: 1. Michael Faraday, who invented an 'induction ring' on August 29, 1831. This was the first transformer, although Faraday used it only to demonstrate the principle of electromagnetic inductionand did not foresee the use to which it would eventually be put. 2. Lucien Gaulard and John Dixon Gibbs, who first exhibited a device called a 'secondary generator' in London in 1881 and then sold the idea to American company Westinghouse. This may have been the first practical power transformer, but was not the first transformer of any kind. They also exhibited the invention in Turinin 1884, where it was adopted for an electric lighting system. Their early devices used a linear iron core, which was later abandoned in favour of a more efficient circular core. 3. William Stanley, an engineer for Westinghouse, who built the first practical device in 1885 after George Westinghouse bought Gaulard and Gibbs' patents. The core was made fro...

    A transformer usually has: 1. two or more insulated windings, to carry current 2. a core, in which the mutual magnetic field couplesthe windings. In transformers designed to operate at low frequencies, the windings are usually formed around an iron or steel core. This helps to confine the magnetic field within the transformer and increase its efficiency, although the presence of the core causes energy losses. Transformers made to operate at high frequencies may use other lower loss materials, or may use an air core. Power transformers are further classified by the exact arrangement of the core and windings as "shell type", "core type" and also by the number of "limbs" that carry the flux (3, 4 or 5 for a 3-phase transformer). The differences in the performance of each of these types, while of continuing interest to specialists, is perhaps more detail than is appropriate for a general encyclopedia.


    An autotransformerhas only a single winding, which is tapped at some point along the winding. AC or pulsed DC power is applied across a portion of the winding, and a higher (or lower) voltage is produced across another portion of the same winding. Autotransformers are used to compensate for voltage drop in a distribution system or for matching two transmission voltages, for example 115 kV and 138 kV. For voltage ratios not exceeding about 3:1, an autotransformer is less costly, lighter, small...

    Polyphase transformers

    For three-phase power, three separate single-phase transformers can be used, or all three phases can be connected to a single polyphase transformer. The three primary windings are connected together and the three secondary windings are connected together. The most common connections are Y-Δ, Δ-Y, Δ-Δ and Y-Y. If a winding is connected to earth (grounded) the earth connection point is usually the center point of a Y winding. There are many possible configurations that may involve more or fewer...

    Resonant transformers

    A resonant transformer is one that operates at the resonant frequency of one or more of its coils. The resonant coil, usually the secondary, acts as an inductor, and is connected in series with a capacitor. If the primary coil is driven by a periodic source of alternating current, such as a square or sawtooth wave, each pulse of current helps to build up an oscillation in the secondary coil. Due to resonance, a very high voltage can develop across the secondary, until it is limited by some pr...

    Electric power transmission over long distances. The simplicity, reliability, and economy of conversion of voltages by stationary transformers was the principal factor in the selection of alternati...
    High-voltage direct-current HVDCpower transmission systems
    Large, specially constructed power transformers are used for electric arc furnaces used in steelmaking.
    Rotating transformers are designed so that one winding turns while the other remains stationary. A common use was the video head system as used in VHS and Beta video tape players. These can pass po...

    Template:Wikibookspar 1. Main : Distributed generation, Electronic power supply, Electronics, Inductor, Pickup, Electrical network, Electricity distribution, Wet transformer, Electronics topics 2. Circuits: Ballast, Clamp meter, Repeating coil, Inverter (electrical), Ignition system, Electricity generation, Linear variable differential transformer, Neon signage, Regulator, Electrical substation, Switched-mode power supply, Technological applications of superconductivity, Tesla coil, Transducer 3. Electromagnetism: Alternating current, Electric power, Electric power transmission, Electromagnetic induction, Equivalent series resistance, High-voltage direct current, Impedance matching, Inductive coupling, Potential difference, Skin effect, Leakage inductance, Superconductivity 4. People: Ottó Bláthy, Miksa Déri, John Ambrose Fleming, Otto A. Knopp, William Stanley, Nikola Tesla, Milan Vidmar, George Westinghouse, Károly Zipernowsky 5. Other: DI unit, Polychlorinated biphenyl, Stafford,...

  10. Transformer wikipedia, the free encyclopedia › bibekloves9 › transformer

    Aug 05, 2013 · In 1891, Nikola Tesla invented the Tesla coil, an air-cored, dual-tuned resonant transformer for generating very high voltages at high-frequency.[112][113] See also Magnetization Inductor Polyphase system Load profile Magnetic core 19.

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