September 14, 2016

What are the advantages and disadvantages of dc motors compared with ac motors?

Advantages and disadvantages of DC motors compared with AC motors:

Advantages of DC Motor:

  • Speed control over a wide range both above and below the rated speed: Speed control of DC motors is much easier, making them more versatile for use where a wide range of speeds is required. 
  • They may be used for dynamic braking; that is, a motor on an electric train will act as a motor when required, but when going downhill, it can be used as a generator, thereby putting current back into the line. 
  • Free from harmonics, reactive power consumption and many factors which make DC motors more advantageous compared to AC induction motors.
  • In generating, it requires power, so it acts as a brake. 
  • Quick starting, stopping, reversing and acceleration.

Disadvantages of DC Motor:

  • High initial cost.
  • DC motors, however, require more maintenance than most AC motors. 
  • Cannot operate in explosive and hazardous conditions due to sparking occur at brush (risk in commutation failure).
  • In order to use a DC motor, special provisions must be made.

Some of the applications of DC motors are Steel mills, paper mills, cranes and elevators, electric trains and much more etc.


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