The field and armature winding of dc series motor is connected in the series and carries the same current. The torque of DC motor is proportional to the field current and armature current. In the case of Dc series motor, the torque becomes square of the armature current. This is why the DC series motor is used for driving heavy loads.
Why DC series motor has high starting torque?
For driving the high inertia loads, higher starting torque is required. The loads like locomotive engines, bucket elevators demand higher starting torque for the motion from its standstill position.
Construction of DC Series Motor
The DC series motor has a field winding and the armature winding. Both the winding are connected in the series and the same magnitude of the current flows through both winding.
The field winding has few turns of thick wire as the full armature current pass through the field winding.
The DC series motor provides high starting torque because the field and armature winding are connected in the series and carry the same current.
The starting torque of the DC series motor is proportional to the square of the armature current. The armature current-Torque characteristics of the DC series motor is as given below.
That is why DC series motor is capable to produce high starting torque, and it is preferred for driving heavy loads.
The high inertia loads like cranes need a high starting torque. The DC series motor is used in cranes.