The greatest percentage of power loss in a d.c. the motor is due to ………………..
Right Answer is:
Constant and Variable Losses
For a DC Machine,
Total Losses = Constant losses + Variable losses
Constant losses are those losses that always occur irrespective of the load conditions and whose value remains constant for a given machine. Mechanical losses, core losses, and shunt field copper losses are included in constant losses.
Variable losses are those losses that increase as the load on the machine is increased. They are electrical losses including armature copper losses, the field winding copper losses, interpole winding copper losses, compensating winding copper losses, and brush contact losses.
Copper losses increase proportionally to the square of the armature current while brush contact losses increase proportional to armature current. These losses are about 30% of the total full load losses.