Synchronous Generator
1.1 SYNCHRONOUS GENERATOR THEORY
The synchronous generator, like all generators works on the principle that when a coil is placed in varying magnetic field, an emf is induced in the coil. Synchronous Generator consists of two main windings, the armature winding and the field winding. The armature winding is on the stator and the field winding is on the rotor. For a three phase generator, the windings of each phase of the armature are displaces by 120 degrees from each other around the inside periphery. The field winding is a coil which carries dc current and hence produces constant magnetic field. Besides the armature and the field windings there is another winding called the damper winding that is present on the rotor .The damper winding is a physically closed coil whose purpose is to provide damping to the oscillations in the rotor. Under steady state this winding has no effect on the generator operation. The field winding may be excited externally or from the armature output of the same generator after rectification.
1.1.1 Working Principle
When the current carrying field winding is rotated, the field produced by it also rotates .This flux also links the armature. Since the field rotates and the armature coils are stationary, the flux linking these armature coils also changes periodically, thereby producing emf which is also periodically varying. Since the three coils of the armature (one for each phase) are 120 degrees apart, the emf induced in one coil has a phase difference of 120 degrees from that in the other coil.
1.1.2 Hunting Phenomena in Synchronous Generator
Under steady state the rotor of the generator keeps on running at synchronous speed. But when some disturbance (e.g. increase in load) occurs the rotor starts oscillating about its equilibrium position (its final load angle) along with rotating synchronously. This phenomenon of oscillation of the rotor is called Hunting.
Consider a synchronous generator in which the rotor is running
The synchronous generator, like all generators works on the principle that when a coil is placed in varying magnetic field, an emf is induced in the coil. Synchronous Generator consists of two main windings, the armature winding and the field winding. The armature winding is on the stator and the field winding is on the rotor. For a three phase generator, the windings of each phase of the armature are displaces by 120 degrees from each other around the inside periphery. The field winding is a coil which carries dc current and hence produces constant magnetic field. Besides the armature and the field windings there is another winding called the damper winding that is present on the rotor .The damper winding is a physically closed coil whose purpose is to provide damping to the oscillations in the rotor. Under steady state this winding has no effect on the generator operation. The field winding may be excited externally or from the armature output of the same generator after rectification.
1.1.1 Working Principle
When the current carrying field winding is rotated, the field produced by it also rotates .This flux also links the armature. Since the field rotates and the armature coils are stationary, the flux linking these armature coils also changes periodically, thereby producing emf which is also periodically varying. Since the three coils of the armature (one for each phase) are 120 degrees apart, the emf induced in one coil has a phase difference of 120 degrees from that in the other coil.
1.1.2 Hunting Phenomena in Synchronous Generator
Under steady state the rotor of the generator keeps on running at synchronous speed. But when some disturbance (e.g. increase in load) occurs the rotor starts oscillating about its equilibrium position (its final load angle) along with rotating synchronously. This phenomenon of oscillation of the rotor is called Hunting.
Consider a synchronous generator in which the rotor is running