Consider the following statements:
To control the speed of a dc shunt motor above the base speed over a reasonably wide range, the motor must
A. 1, 2 and 4 are correct
B. 1, 2 and 3 are correct
C. 1 and 3 are correct
D. 2 and 4 are correct
Answer: A
Share your understanding of this question with the correct explanation.
To control the speed of a DC shunt motor above the base speed over a reasonably wide range, the motor must have a compensating winding, have an interpole winding, and be started using a 4-point starter.
Statement 1: The motor must have a compensating winding. This is correct because a compensating winding helps to improve the commutation of the motor and allows for better speed control at high speeds.
Statement 2: The motor must have an interpole winding. This is correct because an interpole winding, also known as a commutating pole winding, helps to compensate for armature reaction and improves the commutation of the motor at high speeds.
Statement 3: The motor must be started using a 3-point starter. This statement is incorrect because the type of starter used does not directly affect the motor’s speed control above the base speed.
Statement 4: The motor must be started using a 4-point starter. This is correct because a 4-point starter is commonly used for DC motors operating above the base speed and provides better control over the motor’s speed.
Therefore, the correct answer is A. Statements 1, 2, and 4 are correct.