Previous Year Question
Correct answer: B
Explanation
Speed magnitude can be varied by armature-voltage/field control, while direction reversal requires reversing either armature current or field flux (but not both). The control arrangement in option B provides speed control in both rotational directions.
Formula
Step-by-step solution
Correct Answer
B — Ward-Leonard method
Concept and Reasoning
Speed magnitude can be varied by armature-voltage/field control, while direction reversal requires reversing either armature current or field flux (but not both). The control arrangement in option B provides speed control in both rotational directions.
Calculation / Key Relation
T∝ΦIa
reverse either Φ or Ia → reverse torque/direction
Exam Takeaway
To reverse a DC motor, reverse one of armature or field polarity—not both.
Common Mistake
Reversing both armature and field leaves torque direction unchanged.
Common mistake
Reversing both armature and field leaves torque direction unchanged.
Exam tip
To reverse a DC motor, reverse one of armature or field polarity—not both.
Quick method
To reverse a DC motor, reverse one of armature or field polarity—not both.