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Synchronous Reactance
The reactances of synchronous machines comprise a set of characteristic constants used in the theory of synchronous machines. Technically, these constants are specified in units of the electrical reactance (ohms), although they are typically expressed in the per-unit system and thus dimensionless. Since for practically all (except for the tiniest) machines the resistance of the coils is negligibly small in comparison to the reactance, the latter can be used instead of (complex) electrical impedance, simplifying the calculations. Two reactions theory The air gap of the machines with a salient pole rotor is quite different along the pole axis (so called ''direct axis'') and in the orthogonal direction (so called ''quadrature axis''). Andre Blondel in 1899 proposed in his paper "Empirical Theory of Synchronous Generators" the two reactions theory that divided the armature magnetomotive force (MMF) into two components: the direct axis component and the quadrature axis component. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synchronous Machine
Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronous or ''in sync''—and those that are not are ''asynchronous''. Today, time synchronization can occur between systems around the world through satellite navigation signals and other time and frequency transfer techniques. Navigation and railways Time-keeping and synchronization of clocks is a critical problem in long-distance ocean navigation. Before radio navigation and satellite-based navigation, navigators required accurate time in conjunction with astronomical observations to determine how far east or west their vessel traveled. The invention of an accurate marine chronometer revolutionized marine navigation. By the end of the 19th century, important ports provided time signals in the form of a signal gun, flag, or dropping tim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Field Winding
A field coil is an electromagnet used to generate a magnetic field in an electro-magnetic machine, typically a rotating electrical machine such as a motor or generator. It consists of a coil of wire through which the field current flows. In a rotating machine, the field coils are wound on an iron magnetic core which guides the magnetic field lines. The magnetic core is in two parts; a stator which is stationary, and a rotor, which rotates within it. The magnetic field lines pass in a continuous loop or magnetic circuit from the stator through the rotor and back through the stator again. The field coils may be on the stator or on the rotor. The magnetic path is characterized by ''poles'', locations at equal angles around the rotor at which the magnetic field lines pass from stator to rotor or vice versa. The stator (and rotor) are classified by the number of poles they have. Most arrangements use one field coil per pole. Some older or simpler arrangements use a single fie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potier Reactance
Potier is a surname, meaning potter. Notable people with the surname include: * Alfred Potier (1840–1905), French polymath * Benoît Potier (born 1957), French businessman * Charles Potier (1806–1870), French actor and playwright * Dominique Potier (born 1954), French politician * Edgard Potier (1903–1944), Belgian military officer * Jérôme Potier (born 1962), French former tennis player * Joseph Potier (1768—1830), French privateer * Pierre Potier (1934–2006), French pharmacist * Pierre-Philippe Potier (1708–1781), Belgian Jesuit priest and lexicographer * Suki Potier (1947–1981), English model See also * Pottier * Potter (name) Potter is an English surname that originally referred to someone who made pottery. It is occasionally used as a given name. People with the name include: Surname * Albert Potter (1897–1942), English footballer * Alexandra Potter (born 1970), Brit ... * House of Potier Surnames Surnames of French origin French-language surn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zero Sequence
0 (zero) is a number representing an empty quantity. Adding (or subtracting) 0 to any number leaves that number unchanged; in mathematical terminology, 0 is the additive identity of the integers, rational numbers, real numbers, and complex numbers, as well as other algebraic structures. Multiplying any number by 0 results in 0, and consequently division by zero has no meaning in arithmetic. As a numerical digit, 0 plays a crucial role in decimal notation: it indicates that the power of ten corresponding to the place containing a 0 does not contribute to the total. For example, "205" in decimal means two hundreds, no tens, and five ones. The same principle applies in place-value notations that uses a base other than ten, such as binary and hexadecimal. The modern use of 0 in this manner derives from Indian mathematics that was transmitted to Europe via medieval Islamic mathematicians and popularized by Fibonacci. It was independently used by the Maya. Common names for the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Negative Sequence
Negative may refer to: Science and mathematics * Negative number * Minus sign (−), the mathematical symbol * Negative mass * Negative energy * Negative charge, one of the two types of electric charge * Negative (electrical polarity), in electric circuits * Negative result (other) * Negative lens, in optics Photography * Negative (photography), an image with inverted luminance or a strip of film with such an image * Original camera negative, the film in a motion picture camera which captures the original image * Paper negative, a negative image printed on paper used to create the final print of a photograph Linguistics * A negative answer, commonly expressed with the word ''no'' * A type of grammatical construction; see affirmative and negative *A double negative is a construction occurring when two forms of grammatical negation are used in the same sentence. Music * Negative (Finnish band), a Finnish band established in 1997 * Negative (Serbian band), a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Symmetrical Components
In electrical engineering, the method of symmetrical components simplifies the analysis of unbalanced three-phase power systems under both normal and abnormal conditions. The basic idea is that an asymmetrical set of ''N'' phasors can be expressed as a linear combination of ''N'' symmetrical sets of phasors by means of a complex linear transformation. Fortescue's theorem (symmetrical components) is based on the superposition principle, so it is applicable to linear power systems only, or to linear approximations of non-linear power systems. In the most common case of three-phase systems, the resulting "symmetrical" components are referred to as ''direct'' (or ''positive''), ''inverse'' (or ''negative'') and ''zero'' (or ''homopolar''). The analysis of power system is much simpler in the domain of symmetrical components, because the resulting equations are mutually linearly independent if the circuit itself is balanced. Description In 1918 Charles Legeyt Fortescue presented ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synchronous Impedance Curve
The synchronous impedance curve (also short-circuit characteristic, SCC) of a synchronous generator is a plot of the output short circuit current as a function of the excitation current or Field (physics), field. The curve is typically plotted alongside the open-circuit saturation curve. The SCC is almost linear, since under the short-circuit conditions the magnetic flux in the generator is below the iron magnetic saturation, saturation levels and thus the reluctance is almost entirely defined by the fixed one of the air gap (electric machine), air gap. The name "synchronous impedance curve" is due to the fact that in the short-circuit condition all the generated voltage dissipates across the generator internal synchronous impedance Z_S. The curve is obtained by rotating the generator at the rated RPM with the output terminals shorted and the output current going to 100% of the rated for the device (higher values are typically not tested to avoid overheating). References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open-circuit Saturation Curve
The open-circuit saturation curve (also open-circuit characteristic, OCC) of a synchronous generator is a plot of the output open circuit voltage as a function of the excitation current or field. The curve is typically plotted alongside the synchronous impedance curve. At the low field, the permeable iron in the magnetic circuit of the generator is not saturated, therefore the reluctance almost entirely depends on the fixed contribution of the air gap, so the part of the curve that starts at the point of origin is a linear "air-gap line" (output voltage is proportional to the excitation current). As the iron saturates with higher excitation and thus higher magnetic flux, the reluctance increases, and the OCC deflects down from the air-gap line. The curve is obtained by rotating the generator at the rated RPM Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circular Frequency
In physics, angular frequency (symbol ''ω''), also called angular speed and angular rate, is a scalar measure of the angle rate (the angle per unit time) or the temporal rate of change of the phase argument of a sinusoidal waveform or sine function (for example, in oscillations and waves). Angular frequency (or angular speed) is the magnitude of the pseudovector quantity ''angular velocity''. (UP1) Angular frequency can be obtained multiplying ''rotational frequency'', ''ν'' (or ordinary ''frequency'', ''f'') by a full turn (2 radians): . It can also be formulated as , the instantaneous rate of change of the angular displacement, ''θ'', with respect to time, ''t''. (11 pages) Unit In SI |
Armature (electrical)
In electrical engineering, the armature is the winding (or set of windings) of an electric machine which carries alternating current. The armature windings conduct AC even on DC machines, due to the commutator action (which periodically reverses current direction) or due to electronic commutation, as in brushless DC motors. The armature can be on either the rotor (rotating part) or the stator ( field coil, stationary part), depending on the type of electric machine. Shapes of armature used in motors include double-T and triple-T armatures. The armature windings interact with the magnetic field ( magnetic flux) in the air-gap; the magnetic field is generated either by permanent magnets, or electromagnets formed by a conducting coil. The armature must carry current, so it is always a conductor or a conductive coil, oriented normal to both the field and to the direction of motion, torque (rotating machine), or force (linear machine). The armature's role is twofold. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transformer
In electrical engineering, a transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple Electrical network, circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer's core, which induces a varying electromotive force, electromotive force (EMF) across any other coils wound around the same core. Electrical energy can be transferred between separate coils without a metallic (conductive) connection between the two circuits. Faraday's law of induction, discovered in 1831, describes the induced voltage effect in any coil due to a changing magnetic flux encircled by the coil. Transformers are used to change Alternating current, AC voltage levels, such transformers being termed step-up or step-down type to increase or decrease voltage level, respectively. Transformers can also be used to provide galvanic isolation between circuits as well as to couple stages of signa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Gap (magnetic)
Air gap in magnetic circuits is a term used to define an intentional gap left in the magnetic material. In stationary devices, like inductors and transformers, the air gap is used for a few purposes: * to minimize the magnetic saturation of their cores due to the direct current (DC) that might be flowing through the coils. Without saturation the inductance (and thus the blocking capability) of a choke stays constant regardless of the DC current flowing; * counter-intuitively, if a DC magnetization is present in an inductor, an increased (up to some limit) air gap actually incrementally increases the effective inductance; * in a shunt reactor an air gap is used for two reasons: ** with an ungapped core the reluctance is small, so very little reactive power is obtained with the disproportionate effect of the iron loss; ** an increase of the gap reduces the ratio of the total loss to the reactive power, with the limiting factor being the increased heating due to the copper lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
