“dynamo”的概念、定义、翻译、参考文献-科学参考

dynamo

Physics

An electric generator, especially one designed to provide direct current. Alternating-current generators can be called dynamos but are more often called alternators.

Astronomy

The activity in an electrically conducting fluid that generates an electrical current and a magnetic field. Dynamo action in the plasma in the outer layers of the Sun, and in the core or mantle of the Earth and other planets, is thought to produce the magnetic fields of these bodies. See also solar dynamo.

Electronics and Electrical Engineering

An electromagnetic generator that produces either alternating or direct current. It consists of a plane coil that is made to rotate in a uniform magnetic field of flux density B. The coil, of area A, rotates with angular velocity ω; an angle θ is subtended by the normal to the plane of the coil and B. If time t = 0 is chosen so that θ = ωt, then the e.m.f. induced in the coil is given by:
$V = A ω B sin ω t$
This is an alternating voltage, of period ω, that is a maximum when the plane of the coil lies in the direction of the magnetic field.
Alternating current will flow if the two ends of the coil are connected to a pair of slip rings, R and R′ (Fig. a). The ends of the coil can be connected to a commutator by means of semicircular segments, D, making contact with a pair of carbon brushes, C (Fig. b). Then the voltage in each terminal always has the same sign since each segment moves to the next brush as the e.m.f. changes sign. This produces a direct current in a load connected across the brushes. The current is not steady however since the induced voltage is alternating. The fluctuations about the mean value are known as ripple.
(a) Slip-ring operation of a dynamo
(b) Carbon-brush operation of a dynamo
The ripple may be reduced using a drum armature. This has the coil wound around a drum-shaped armature so as to produce several plane coils symmetrically spaced around the drum (Fig. c); each vertical conductor forms a pole. The brushes are placed opposite each pole and are connected in pairs. The effect is to superimpose a number of voltage waveforms all varying slightly in phase (Fig. d). The output voltage has a higher mean value and less magnitude of ripple than that of the single coil. The period of the ripple voltage, which corresponds to the time interval at which successive conductors occupy the same position, is also much higher.
(c) 12-pole drum armature
(d) Voltage waveforms

单词	dynamo
释义	dynamo Physics An electric generator, especially one designed to provide direct current. Alternating-current generators can be called dynamos but are more often called alternators. Astronomy The activity in an electrically conducting fluid that generates an electrical current and a magnetic field. Dynamo action in the plasma in the outer layers of the Sun, and in the core or mantle of the Earth and other planets, is thought to produce the magnetic fields of these bodies. See also solar dynamo. Electronics and Electrical Engineering An electromagnetic generator that produces either alternating or direct current. It consists of a plane coil that is made to rotate in a uniform magnetic field of flux density B. The coil, of area A, rotates with angular velocity ω; an angle θ is subtended by the normal to the plane of the coil and B. If time t = 0 is chosen so that θ = ωt, then the e.m.f. induced in the coil is given by: $V = A ω B sin ω t$ This is an alternating voltage, of period ω, that is a maximum when the plane of the coil lies in the direction of the magnetic field. Alternating current will flow if the two ends of the coil are connected to a pair of slip rings, R and R′ (Fig. a). The ends of the coil can be connected to a commutator by means of semicircular segments, D, making contact with a pair of carbon brushes, C (Fig. b). Then the voltage in each terminal always has the same sign since each segment moves to the next brush as the e.m.f. changes sign. This produces a direct current in a load connected across the brushes. The current is not steady however since the induced voltage is alternating. The fluctuations about the mean value are known as ripple. (a) Slip-ring operation of a dynamo (b) Carbon-brush operation of a dynamo The ripple may be reduced using a drum armature. This has the coil wound around a drum-shaped armature so as to produce several plane coils symmetrically spaced around the drum (Fig. c); each vertical conductor forms a pole. The brushes are placed opposite each pole and are connected in pairs. The effect is to superimpose a number of voltage waveforms all varying slightly in phase (Fig. d). The output voltage has a higher mean value and less magnitude of ripple than that of the single coil. The period of the ripple voltage, which corresponds to the time interval at which successive conductors occupy the same position, is also much higher. (c) 12-pole drum armature (d) Voltage waveforms
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