To keep it short we can conclude that to get steady state torque and to synchronize the rotor we use dc excitation. If you use AC excitation, flux will be alternating. … For dynamically induced emf, you need a constant flux (provided by DC excitation) and a rotating coil. This is the basic principle of DC/AC generator.
What is the use of DC excitation in AC generator?
A generator has a prime mover like a turbine or diesel generator. The excitation system creates the electromagnetic field in the rotor. The stator has the armature winding that has the electrical energy induced. The stronger the magnetic field created, the stronger the electrical power produced.
Why is excitation needed?
The excitation system is responsible for supplying the field current to the main rotor. The requirements of an excitation system include reliability under all conditions of service, a simplicity of control, ease of maintenance, stability and fast transient response.
What is excitation EMF?
The process of generating a magnetic field by means of an electric current is called excitation. Field coils yield the most flexible form of magnetic flux regulation and de-regulation, but at the expense of a flow of electric current.
Why exciter is used in generator?
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.
What is excitation current in a generator?
The excitation system monitors the generator output and regulates the magnetic field to maintain the desired voltage. As the load on the generator is increased, an increase in current flow causes the voltage to drop.
Why the synchronous motor is not self starting?
Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator. … Once the rotor nears the synchronous speed, the field winding is excited, and the motor pulls into synchronization.