DC motor starter is used to ___?

By BYJU'S Exam Prep

Updated on: September 25th, 2023

(A) Reduce the armature winding resistance

(B) Control the initial current

(C) Increase the winding resistance of the field

(D) Reduce the back EMF.

DC motor starter is used to control the initial current. A starter is necessary to start a DC motor because it restricts the initial high armature current that exists, as the value of starting back-EMF is zero.

Why DC Motor Starter is Used To Control Initial Current?

A resistor is used in the starter for a DC shunt motor. In order to prevent damage from being done to DC motors during startup due to extremely high current and torque, starters are utilized. They achieve this by connecting the motor’s armature winding in series with external resistance, which limits the current to a manageable amount.

By looking at the voltage equation of a DC motor, we may determine why certain motors have high startup current:

E = Eb + Ia Ra

Where:

E = supply voltage

Eb = back EMF

Ia = armature current

Ra = armature resistance

Since back EMF is inversely related to motor speed, it is also 0 at startup when the motor speed is zero. As a result, we can show that, at startup, armature current is inversely proportional to armature resistance by deleting the Eb part and rearranging the voltage equation.

Ia = E/Ra

Summary:

DC motor starter is used to ____ (A) Reduce the armature winding resistance (B) Control the initial current (C) Increase the winding resistance of the field (D) Reduce the back EMF

DC Motor Starters are used to protect DC motors from damage due to high current flow in the start process. A starter restricts high current as the starting back EMF is zero.

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