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  1. Template:COVID-19 pandemic data - Wikipedia

    en.wikipedia.org › wiki › Template:COVID-19_pandemic_data

    Usage. This template is used to provide data for COVID-19 pandemic and COVID-19 pandemic by country and territory. It uses { { Cases in the COVID-19 pandemic }} to update the total numbers. Before making major changes, use the sandbox linked ...

  2. Aluminium alloy - Wikipedia

    en.wikipedia.org › wiki › Aluminium_alloy

    Aluminium alloy. Welded aluminium alloy bicycle frame, made in the 1990s. Aluminium alloys (or aluminum alloys; see spelling differences) are alloys in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, ...

  3. Transformer - Wikipedia

    en.wikipedia.org › wiki › Transformer
    • Principles
    • Construction
    • Classification Parameters
    • Applications
    • History
    • Bibliography

    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...

    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}}}

    Polarity

    A dot convention is often used in transformer circuit diagrams, nameplates or terminal markings to define the relative polarity of transformer windings. Positively increasing instantaneous current entering the primary winding's ‘dot’ end induces positive polarity voltage exiting the secondary winding's ‘dot’ end. Three-phase transformers used in electric power systems will have a nameplate that indicate the phase relationships between their terminals. This may be in the form of a phasordiagra...

    Cores

    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...

    Windings

    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...

    Cooling

    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...

    Beeman, Donald, ed. (1955). Industrial Power Systems Handbook. McGraw-Hill.
    Calvert, James (2001). "Inside Transformers". University of Denver. Archived from the original on May 9, 2007. Retrieved May 19, 2007.
    Coltman, J. W. (Jan 1988). "The Transformer". Scientific American. 258 (1): 86–95. Bibcode:1988SciAm.258a..86C. doi:10.1038/scientificamerican0188-86. OSTI 6851152.
    Coltman, J.W. (Jan–Feb 2002). "The Transformer [Historical Overview]". IEEE Industry Applications Magazine. 8 (1): 8–15. doi:10.1109/2943.974352. S2CID 18160717.
  4. New Zealand - Wikipedia

    en.wikipedia.org › wiki › New_zealand

    New Zealand (Māori: Aotearoa [aɔˈtɛaɾɔa]) is an island country in the southwestern Pacific Ocean.It consists of two main landmasses—the North Island (Te Ika-a-Māui) and the South Island (Te Waipounamu)—and more than 700 smaller islands, [13] ...

  5. List of jōyō kanji - Wikipedia

    en.wikipedia.org › wiki › Joyo_kanji_list

    ... translation is given per kanji. The "Grade" column specifies the grade in which the kanji is taught in Elementary schools in Japan.Grade "S" means that it is taught in secondary school. The list is sorted by Japanese ... ...

  6. Morocco - Wikipedia

    en.wikipedia.org › wiki › Morocco

    Morocco, [a] officially the Kingdom of Morocco, [b] is the northwesternmost country in the Maghreb region of North Africa.It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to ...

  7. Russia - Wikipedia

    en.wikipedia.org › wiki › Russia

    Russia (Russian: Россия, Rossiya, Russian pronunciation: [rɐˈsʲijə]), or the Russian Federation, [b] is a country spanning Eastern Europe and Northern Asia.It is the largest country in the world by area, covering over 17 million square ...

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