DC motor construction and working

Introduction:- A DC motor is a device / machine which converts DC power to mechanical energy. It consist of a stationary outer body known as yoke and a rotating armature inside the yoke. Yoke holds main field poles and inter-poles with the help of bolts.Two end covers are fixed on each side of yoke they supports armature with the help of bearings. Armature consist of a shaft armature core, armature winding commutator. Rocker arm holds the brush holders is fixed on free end side end shield. Carbon brushes are hold by brush holder and maintain proper brush position and pressure on commutator.

Magnetic Circuit of DC Motor:- It consist of Main Pole body, Pole Shoe  Armature core again Pole shoe Main pole body and returns through yoke body as shown in diagram.

Electrical circuit consist of field winding and armature winding. Main field winding produces main working flux in motor is wound on main poles. All four poles windings are connected in series. Final two leads of main field winding  are connected to rated supply voltage. This winding is known as shunt field winding as it is connected in parallel to supply voltage. Series field winding is also wound on main poles. All four pole coils are connected in series. Final two leads are connected in series with armature winding. Series winding helps the maintain flux lavel during load condition.Interpole winding is wound on interpoles and is connected in series with armature winding. Interpole winding helps to improve commutation. when supply is given to field winding it produces flux. The supply given to armature produces set of current carring conductors in magnetic field which causes production of tourqe on armature. So armature start rotating. The direction of motor can be changed by changing the polarity of either shunt field winding or armature winding. The speed of motor is proportional to applied voltage to armature and inversaly proportional to field winding current.