Difference Between AC And DC Motor

Hello guys, welcome back to my blog. In this article, I will discuss the difference between AC and DC motor.

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Also read – Electrical Machines Questions And Answers.

  • AC motor: Mainly for industrial applications, agriculture, commercial, domestic, etc.
  • DC motor: For the domestic appliances and also for special purposes we use these dc motors in the industries or commercial purposes.

01. The ac motors are supplied with alternating currents that have frequency whereas the dc motors are supplied by the direct current and there is no frequency in dc.

02. In the ac motors, except 3 phase induction motor all are not self-starting motors because of the absence of a rotating magnetic field for creating that RMF, in the synchronous motor, we give the rotor dc supply. For the single-phase motors we will connect an auxiliary winding across armature winding to create RMF and to start the motor, whereas in dc motors all are self-starting motors.

03. In the ac motor, we do not require any commutator because we do not want to convert supply, whereas in dc motors we require the commutator for converting supply.

04. There is no requirement of brushes in the ac motors .we require brushes in dc motors.

05. In ac motors, we have single-phase (phase and neutral) and 3 phase (RYB, red, yellow, blue we have three terminals) motor whereas in dc motors we have only positive and negative terminals to give input to the motor.

06. In the ac motors, the stator is standstill and provides the rotating magnetic field to the rotor to rotate and in the dc motors the field winding is at a standstill and the armature rotates.

07. In the ac motors, the speed is controlled by the changing frequency or V/F method whereas in dc motors the speed is controlled by changing the armature current method.

08. In the ac motor if the load changes suddenly the response of the motor is slow and in dc motor if the load changes suddenly the response of the motor is quick and accurate.

09. The dc motors mainly used for variable speed and high torque whereas the ac motors are used for the variable torque and high speed.

10. The maintenance cost of the dc motor is expensive because of the commutator and brushes whereas in the ac motor, the cost is less because of the absence of commutator and brushes.

11. In the efficiency point of view, the ac motor is less efficient because of current loss and motor slip whereas the dc motor is more efficient because of the absence of current loss and slips in the motor.

12. The life of an ac motor is more because no commutator and brushes are used in motor and the life span of the dc motor is limited because of the commutator and brushes.

13. The starters used for ac motors are DOL starter, star-delta starter, auto-transformer starter, soft starter, etc. The starters used for dc motors are a three-point starter and four-point starter.

Conclusion: You can buy a motor based on your requirement. First, see whether you want a motor of high starting torque or high speed or low energy consuming motor, etc.

These are the difference between ac and dc motor. I hope this article may help you all a lot. Thank you for reading.

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Chetan Shidling

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