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These days DC motors are widely used in
pumping sets
air compressors
electric traction
machine shops
electric traction
DC series motors are widely used in electric traction because they possess a high starting torque and their speed is inversely proportional to the torque, making them ideal for accelerating heavy loads like trains.
DC series motors are widely used in electric traction because they possess a high starting torque and their speed is inversely proportional to the torque, making them ideal for accelerating heavy loads like trains.
TaтАЛтИЭ╬жIaтАЛ тАФ Basic torque equation for DC machines
TaтАЛтИЭIa2тАЛ тАФ Torque for DC series motors (below magnetic saturation)
The DC series motor exhibits a torque-speed characteristic where TтИЭIa2тАЛ at low speeds (before saturation) and NтИЭIaтАЛ1тАЛ. This allows the motor to provide massive starting torque for heavy trains while naturally slowing down as the load increases, effectively handling the high inertia requirements of traction systems.
DC series motors have a characteristic of very high starting torque.
The speed of a DC series motor varies inversely with the load.
Electric traction requires high initial acceleration and the ability to handle varying loads.
Series motors can handle heavy surge currents effectively.
High starting torque
Self-relieving property with increasing load
Simple control with series-parallel switching
Risk of 'runaway' at light loads or no-load conditions
Requires maintenance due to the commutator and brushes
Electric locomotives
Heavy-duty cranes
Hoists and conveyors
Never operate a DC series motor at no-load, as the speed becomes dangerously high (NтИЭ╬ж1тАЛ and ╬жтЖТ0 at no-load).
Option A (pumping sets) usually uses Shunt or Induction motors for constant speed operation.
Option D (machine shops) typically uses DC shunt motors for constant speed requirements.
C is correct тАФ DC series motors are specifically chosen for electric traction due to their high starting torque capability and variable speed characteristics suitable for heavy-load acceleration.
In competitive exams, always remember: for constant speed tasks use DC Shunt motors, and for high starting torque/traction tasks use DC Series motors.