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Which of the following methods could be used to start a Three-phase cage-type induction motor? I. Direct-on-line starting II. Auto-transformer starting III. Star-delta starting Choose the correct answer from the options given below.

Which of the following methods could be used to start a Three-phase cage-type induction motor? I. Direct-on-line starting II. Auto-transformer starting III. Star-delta starting Choose the correct answer from the options given below. Correct Answer I, II and III

Methods used to start a three-phase cage-type induction motor

DOL starter:

  • The direct on line (DOL) starter method of an induction motor is simple and economical.
  • In this method, the starter is connected directly to supply voltage.
  • In this method, small motors up to 5 hp rating are started to avoid the supply voltage fluctuation.

 

Star-delta starter:

  • The star-delta starter method of starting three-phase induction motors is very common and widely used among all the methods.
  • In this method, at stating motor in star connection and runs at delta connected stator windings.

 

Auto-transformer starter:

  • The Autotransformer is used in both the type of the connections, i.e., either star connected or delta connected.
  • The autotransformer is used to limit the starting current of the induction motor.
  • This method is used for the high rating of squirrel cage induction motors. So, this method is most suitable for a 20 hp squirrel cage induction motor.
  • The auto-transformer starter is expensive compare to the “direct on line” (DOL) starter

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