Why do synchronous generators need DC excitation?

The primary reason lies in the principle of operation of Synchronous machines. The rotor acts as an electromagnet with a constant flux and gets interlocked with the rotating flux of stator to provide a constant speed rotation. The rotor needs to have a constant flux and that’s why the dc excitation is provided.

Why is DC used for excitation?

Why only D.C is used for Excitation in Alternators? Excitation voltage or current is supplied to the field windings of a rotor to produce a static magnetic field. If we use alternating current instead of direct current; we will get a fluctuating magnetic field.

What is excitation AC excitation and DC excitation?

The DC excitation system has two exciters – the main exciter and a pilot exciter. The exciter output is adjusted by an automatic voltage regulator (AVR) for controlling the output terminal voltage of the alternator. The current transformer input to the AVR ensures limiting of the alternator current during a fault.

What is DC field excitation of synchronous generator?

The DC output of the main exciter is given to the field winding of the synchronous machine through brushes and slip rings. The pilot exciter is excluded in smaller machines. For medium-size machines, AC Exciters are used in place of DC Exciter. AC Exciters are three-phase AC generators.

Do synchronous motors use AC or DC?

In a synchronous motor, AC power is supplied to the stator to generate a rotating magnetic field. DC power is supplied to the rotor which results in discrete North (N) and South (S) poles.

What is excitation system explain DC excitation system of synchronous machine?

What is an Excitation System? Definition: The system which provides DC to the synchronous machine field winding to perform protective & control functions of the power system. This system consists of exciter, PSS (Power System Stabilizer), AVR (Automatic Voltage Regulator), processing unit, and measuring elements.