Operation of power generators is based on the Electromagnetic Induction. whenever a conductor moves relative to magnetic field, voltage is induced in the conductor. If a coil is spinning in a magnetic field, then the two sides of the coil move in opposite directions, and the voltages induced in each side add. The instantaneous value of the resulting voltage (called electromotive force, emf) is equal to the minus of the rate of change of magnetic flux Φ times the number of turns in the coil: V=−N•∆Φ/Δt. This relationship has been found experimentally and is referred to as Faraday's law. The minus sign here is due to Lenz law, which states that the direction of the emf is such that the magnetic field from the induced current opposes the change in the flux which produces this emf. Lenz law is connected to the conservation of energy.
.Since the rate of magnetic flux change through the coil that spins at a constant rate changes sinusoid ally with the rotation, the voltage generated at the coil terminals is also sinusoidal (AC). If an external circuit is connected to the coil's terminals, this voltage will create current through this circuit, resulting in energy being delivered to the load. Thus, the mechanical energy that rotates the coil is converted into electrical energy. Note that the load current in turn creates a magnetic field that opposes the change in the flux of the coil, so the coil opposes the motion. The higher current, the larger force must be applied to the armature to keep it from slowing down. In the animation the coil is rotated by the hand crank. In practice, the mechanical energy is produced by turbines or engines called prime movers.
The production of voltage depends only on the Relative Motion between the coil and the magnetic field. Voltage is induced by the same physics law whether the magnetic field moves past a stationary coil, or the coil moves through a stationary magnetic field. In the animation, the magnetic field is produced by a stationary magnet while the coil is revolving. In AC generators, usually the field is spinning and the power-producing armature is stationary. This armature comprises of a set of coils that form a cylinder. Also, in practice, the magnetic field is usually induced by an electromagnet rather then a permanent magnet.
.Since the rate of magnetic flux change through the coil that spins at a constant rate changes sinusoid ally with the rotation, the voltage generated at the coil terminals is also sinusoidal (AC). If an external circuit is connected to the coil's terminals, this voltage will create current through this circuit, resulting in energy being delivered to the load. Thus, the mechanical energy that rotates the coil is converted into electrical energy. Note that the load current in turn creates a magnetic field that opposes the change in the flux of the coil, so the coil opposes the motion. The higher current, the larger force must be applied to the armature to keep it from slowing down. In the animation the coil is rotated by the hand crank. In practice, the mechanical energy is produced by turbines or engines called prime movers.
The production of voltage depends only on the Relative Motion between the coil and the magnetic field. Voltage is induced by the same physics law whether the magnetic field moves past a stationary coil, or the coil moves through a stationary magnetic field. In the animation, the magnetic field is produced by a stationary magnet while the coil is revolving. In AC generators, usually the field is spinning and the power-producing armature is stationary. This armature comprises of a set of coils that form a cylinder. Also, in practice, the magnetic field is usually induced by an electromagnet rather then a permanent magnet.
The electromagnet consists of so called field coils mounted on an iron core. A current flow in the field coils produces the magnetic field. This current may be obtained from an external source or from the system's own armature. Regulation is achieved by sensing the output voltage, converting it to a DC, and comparing its level to a reference voltage. An error is used to control the field in order to maintain a constant output. Most modern AC sources with field coils are Self-Excited: the current for field coils is supplied by an additional exciting winding in the armature.
really it is excellent idea about the working procedure of AC Generator.it is informative for me.and it made various part as Motor Slip Ring
ReplyDelete