The main purpose of exciter in a generator(alternator) is to provide stationary rotating magnetic field. Which is used to induce the e.m.f in the armature coil. So, DC power is given to exciter and the exciter is nothing but a coil, and the exciter creates a magnetic field..
In this regard, how does an exciter field work?
In the past, the exciter was a small DC generator coupled to the same shaft as the rotor. Therefore, when the rotor rotates this exciter produces the power for the electromagnet. This output from the exiter then controls the magnetic field of the rotor to produce a constant voltage output by the generator.
Beside above, how does a brushless exciter work? A brushless exciter does not use slip rings to provide the DC voltage for the rotors magnetic field. The induced current is converted to DC by the rotating rectifier, providing excitation voltage for the windings of the rotor poles.
Simply so, why is excitation needed?
The more excitation is needed in the system when the load current is large, the speed is less, and the power factor of the system becomes lagging. The excitation system is the single unit in which the each alternator has its exciter in the form of generator.
What is a motor exciter?
The motor is started as an induction motor and as it reaches slip speed the rotor field is supplied with the rated DC Voltage. The exciter provides the power to the electromagnets that form the poles on the rotor that in turn follow the rotating magnetic field from the system.
Related Question Answers
Why DC is used for excitation?
For successful operation of alternator it must produce sinusoidal AC voltage at a particular frequency. Now, dc excitation produce a fixed polarity electromagnet in field which runs at a constant speed by the prime mover. Thus it produce almost a sinusoidal AC by the stator armature.How does an AVR work?
An automatic voltage regulator (AVR) is an electronic device for automatically maintaining generator output terminal voltage at a set value under varying load and operating temperature. It controls output by sensing the voltage Vout at a power-generating coil and comparing it to a stable reference.What is exciting a generator?
Exciter is a small generator, mounted on the same shaft as that of the main generator, which produces DC power for the main generator field winding. Many variety of exciters are available, but the most popular today is brushless exciter.What does it mean to excite a generator?
An electric generator or electric motor consists of a rotor spinning in a magnetic field. The magnetic field may be produced by permanent magnets or by field coils. The process of generating a magnetic field by means of an electric current is called excitation.Why do synchronous generators need excitation?
Synchronous motor excitation refers to the DC supply given to rotor which is used to produce the required magnetic flux. CASE 2: If the field current is not sufficient enough to produce the required air gap flux as demanded by V, additional magnetizing current or lagging reactive VA is drawn from the AC source.How many types of excitation are there?
nineteen different
What is field current?
Definition of field current. : the current supplied to the field windings of a generator or motor to establish the magnetic field for its operation.What is AVR in generator?
An automatic voltage regulator (AVR) is a electronic device for automatically maintaining generator output terminal voltage at a set value under varying load and operating temperature. In such machines, when an alternator is loaded, its terminal voltage drops due to its internal impedance.What is an excitation voltage?
An excitation voltage is the amount of direct voltage required to excite a certain field coil. Excitation is required to create magnetic field around the coils . By cutting this magnetic flux lines EMF is induced across the armature …What is over excitation and under excitation?
Thus the over excited synchronous generator generates more reactive power on this principle. Similarly Under excited synchronous generator absorbs reactive power as when it is under excited means the DC excitation of the synchronous generator has been reduced, which results in decrease in magnetic flux of stator.What happen when generator loss excitation?
When a generator loses its excitation, the rotor current gradually decreases and the field voltage decays by the field time constant as well. In this case, the generator operates as an induction generator and draws reactive power from the power system instead of generating reactive power.What is meant by reactive power?
Reactive power is the part of complex power that corresponds to storage and retrieval of energy rather than consumption. On an AC power system, there are two kinds of power - real power that actually does work, and reactive power that enables transformers to transform, generators to generate, and motors to rotate.What is static excitation system?
Static system - excitation is provided by field winding wound on the rotor therefore Slip Rings and Carbon brushes are used. There are no moving components and usually provides a much faster response which improves stability. It is most commonly used in hydro generators.Why do we need excitation system for alternator?
Originally Answered: Why does an alternator need excitation? The field windings on the rotor (shaft) of an alternator need to be energized (creating field excitation) in order to create a magnetic field to induce voltage when passed through the conductors of the alternator's armature.How does a self excited generator work?
Most of the shunt DC generators work on the principle of self-excitation. Following a positive feedback like action, the flux in a self-excited DC generator, builds up from a small amount of residual magnetism present in the field poles. In self-excited DC generators, the field winding is connected across the armature.What is meant by brushless excitation system?
Brushless Excitation System is a technology for providing the field current to the Synchronous Generator without using Slip Ring and Carbon Brushes. Also, in case of initial start up of Generator we don't need to supply external power source to Brushless Exciter as is the case in Static Excitation System.What is meant by induction motor?
Definition of induction motor. : an alternating-current motor in which torque is produced by the reaction between a varying magnetic field generated in the stator and the current induced in the coils of the rotor.Are alternators brushless?
Brushless alternators A brushless alternator is composed of two alternators built end-to-end on one shaft. Until 1966, alternators used brushes with rotating field. With advancement in semiconductor technology, brushless alternators are possible.Can a brushless motor be used as a generator?
Permanent magnet BLDC motors can be used as generators. There is a type of brushless motor called a Reluctance Motor, which has soft-iron core, so will generate nominally zero voltage when spun. Brushless DC motors are usually motors that have permanent magnet rotors. 
