Which among the following starter CANNOT be used in DC motor?

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ALP CBT 2 Electrician Previous Paper: Held on 22 Jan 2019 Shift 1

Answer 1

A star-delta starter is the most commonly used method for the starting of a 3 phase induction motor.
In star-delta starting an induction motor is connected in through a star connection throughout the starting period.
When the motor reaches about 80% of its full load speed, it will begin to run in a delta connected stator winding.
There are various types of dc motor starters, such as 2 point starter, 3 point starter, 4 point starter, no-load release coil starter, thyristor controller starter, etc.
The basic concept behind every DC motor starter is adding external resistance to the armature winding during starting.
3 point starters and 4 point starters are used for starting dc shunt-wound motors and dc compound wound motors.
2 point starter is used for starting dc series motors.
However, very small dc motors may be started directly by connecting them to the supply with the help of a contractor or a switch. It does not result in any harm because they gather speed quickly due to small rotor inertia.
In this case, the large starting current will die down quickly because of the fast rise in the back emf.