发电机和交流发电机
Broadly defining, a generator is a generic term for a device that converts mechanical energy to electrical energy, and an alternator is a type of generator that generates an alternating current.
More about Electric Generator
The fundamental principle behind the operation of any electrical generator is Faraday’s law of electromagnetic induction. Idea stated by this principle is that, when there is a change of the magnetic field across a conductor (a wire for example), electrons are forced to move in a direction perpendicular to the direction of the magnetic field. This results in generating a pressure of electrons in the conductor (electromotive force), which results in a flow of electrons in one direction.
来be more technical, a time rate of change in magnetic flux across a conductor induces an electromotive force in a conductor, and its direction is given by Fleming’s right hand rule. This phenomenon is used largely to produce electricity.
来achieve this change in magnetic flux across a conducting wire, magnets and the conducting wires are moved relatively, such that flux varies based on the position. By increasing the number of wires, you can increase the resulting electromotive force; therefore wires are wound into a coil, containing a large number of turnings. Setting either the magnetic field or the coil in rotational motion, while the other is stationary allows continuous flux variation.
A rotating part of the generator is called a Rotor, and the stationary part is called a stator. The emf generating part of the generator is referred to as the Armature, while the magnetic field is simply known as Field. Armature can be used as either the stator or the rotor, while the field component is the other.
Increasing the field strength also allows increasing the induced emf. Since permanent magnets cannot provide the intensity needed to optimize the power production from the generator, electromagnets are used. A much lower current is flowing through this field circuit than the armature circuit and lower current pass through the slip rings, which keep the electrical connectivity in the rotator. As a result, most of the AC generators have the field winding on the rotor and the stator as the armature winding.
More about Alternator
Alternators are operating on the same principle as the generator, uses a rotor winding as the field component and armature winding as the stator. The difference there is no alterations in polarizations of the windings are needed; therefore, the contact for the windings are not given by a commutator, as in a DC generator, but directly connected. Most alternators use three stator windings hence the alternator output is a three phase current. The output current is then rectified through bridge rectifiers.
The current to the rotor winding can be controlled; as a result, the output voltage of the alternator can be controlled.
The most common usage of the alternators is in automobiles, where the mechanical energy of the engine supplied to the rotor shaft (through the crank shaft) is converted to the electrical energy, and then used to recharge the accumulator battery in the vehicle.
发电机和交流发电机
• Generator is a generic class of devices, while the alternator is a type of generator producing AC current.
• Alternators use voltage regulators and rectifiers to create a DC output, while in other generators DC current is obtained by adding a commutator or AC current is produced.
• Alternator output can have varying frequencies due to changes in the rotor frequency (but it has no effect because the current is rectified to DC), while the other generators are operated to a constant frequency of the rotor shaft.
• Alternators are used in automobiles, to generate electrical power.
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