
Concept explainers
Explain the necessity of starter on a DC motor.

Explanation of Solution
A starter is an electrical device used to start and accelerate a motor. It is used to limit the inrush current.
Consider the equation of armature current in a DC motor as follows:
Here,
When a motor is started, the armature is stationary at the moment and no counter EMF will be generated. Therefore,
As the counter emf is zero, equation (1) becomes as follows:
Typically, a motor armature resistance is very low. From equation (2), the armature current is inversely proportional to the armature resistance where the armature current is high at the starting of a motor. This high current can create damage to the windings, commutator, and brushes.
Therefore, a starter is used to limit the excessive flow of current and prevent damage to the motor due to the lack of a counter emf and inductive reactance.
Conclusion:
Thus, the necessity of starter on a DC motor is explained.
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Chapter 44 Solutions
Electric Motor Control
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