Why field winding is not excited by AC?

The simple answer is if we give AC supply to the field winding of the synchronous motor then the magnetic locking between the stator field and rotor field will not be created. We know that the opposite pole can attract each other. This was the reason Why DC is used not AC for excitation of Synchronous Motor.

Is the field winding excited with AC or DC?

Three phase AC supply is applied to the armature windings. Field winding in alternators are used to produce the magnetic field needed to excite the generator. The field winding is excited by a small DC supply. The armature winding operates at much higher voltages than the field winding.

What is the effect of excitation on alternator?

The excitation system on a AC alternator refers to the way the alternators voltage is initially built when rotated and controlled while in use. The excitation system is responsible for supplying the field current to the main rotor.

Is it effective to apply AC excitation voltage to the rotor of an AC machine?

To answer the original question, it is entirely possible to apply AC on both the rotor and the stator of a synchronous machine, as long as the current flowing in the coils doesn’t exceed the coil rating, but there is no benefit to doing so.

What is an excitation winding?

Excitation systems can be defined as the system that provides field current to the rotor winding of a generator. Well-designed excitation systems provide reliability of operation, stability and fast transient response. The four common excitation methods include: Permanent Magnet Generator (PMG) Auxiliary Winding (AUX).

What is field excitation?

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 we give DC excitation to the field of an alternator?

Originally Answered: Why dc is used as excitation of alternator? Its because you need a constant field. If you give ac it produces a time varying field. In a constant field the armature cuts the flux, hence a time varying emf is induced.

What happens if the field winding of the synchronous motor is?

In the case of an induction motor, the field winding is permanently short-circuited by end rings. In a Synchronous motor, the rotor winding is supplied with DC excitation. Therefore if we short circuit the field winding of a synchronous motor then it will behave as an induction motor.

What is the function of field winding?

Field winding is used in alternators and synchronous motors. The purpose of the field winding is to create a rotating magnetic field inside the equipment. In alternator the rotation will be initiated from outside and for the synchronous motor it will be from inside.

What is the function of the AC excitation winding?

The basic function of an excitation system is to provide a continuous (DC) current to the field winding of a synchronous machine. This is achieved through the use of closed-loop control (or feedback control).

What is excitation voltage in alternator?

What is Excitation Voltage? An excitation voltage or current is the amount of electric energy ( D.C ) feed into the field winding of an alternator rotor to produce magnetic flux / field. The output voltage of an alternator depends upon the magnetic field and so the excitation voltage.

What happens if the field winding of synchronous motor is short circuited?