1.1 Introduction
In the rotating electrical machine an electromechanical energy conversion take place. In all rotating electrical machine a changes in flux is closely associated with the mechanical motion to cause electromechanical energy conversion. When mechanical input energy is converted to an electrical energy the machine is called generator. The electrical energy is produce in the form of generated voltage or emf. If this emf is constant the machine is called DC generator . While if it is alternating the machine is called motor. If input electrical energy is in the form of AC voltage then it is called AC motor. Thus various electrical rotating machine are classified as AC and DC machine.
Whenever there is relative motion between conductor and flux the emf is induced in a conductor. This is the principle of generator while whenever current carrying conductor is placed in magnetic field then it experiences a mechanical force which is the principle of motor.
Every rotating machine must posses the following parts.
-
Stationary member called stator
-
Rotating member called rotor
-
Shaft
-
Slip ring or brush assembly
-
Bearing
These are the mechanical part which machine are posses. In addition to this machine has
-
An arrangement of winding which is used as primary source of flux. When current is passed through it. This is called field winding or exciting winding.
-
An arrangement of conductor to form a winding in which the emf is induced this is called armature winding.
-
The current flowing through filed winding used to produced main flux called magnetising current, exciting current or filed current.
-
The current flowing through armature winding varies as load on machine varies it is called load current or armature current.
-
The current in field winding is always DC there is an appropriate air gap between a stator and rotor of machine.
In most of machine armature winding is place on stator while field winding is placed on rotor from practical convince point of view.