tricallite

Commutation in DC Machine or Commutation in DC Generator or Motor The  voltage  generated in the armature, placed in a rotating  magnetic field , of a  DC generator  is alternating in nature. The  commutation in DC machine  or more specifically  commutation in DC generator  is the process in which generated alternating  current  in the  armature winding  of a dc machine is converted into direct current after going through the commutator and the stationary brushes. Again in  DC Motor , the input DC is to be converted in alternating form in armature and that is also done through commutation. This transformation of current from the rotating armature of a DC machine to the stationary brushes needs to maintain continuously moving contact between the commutator segments and the brushes. When the armature starts to rotate, then the coils situated under one pole (let it be N pole) rotates between a positive brush an...

Definition of Magnetic Saturation Magnetic Saturation of Iron Now if we try to work with flux density above this limit, the iron exhibits higher reluctance compared to that at low flux density. As a result the said iron or steel does not behave like good  conductor  of magnetic flux. At that situation much more mmf is required to drive the flux through the same iron core. More mmf means more ampere turn in the case of electromagnetic, hence this situation should avoid. Relation between Reluctance and Flux Density In the above figure it is seen that, when flux density is within limit, the reluctance of the magnetic path is quite low but when it crosses certain value such as 2 Tesla as shown here, the reluctance of the same magnetic path is sharply increased. To avoid the undesirable effect of the  magnetic saturation , the size of the iron core suitably chose for a particular engineering application. Generally volume of the iron or steel core of magnetic path in a machi...