Electrician Red Seal · Question
What is the primary function of an interlocking contact (e.g., normally closed auxiliary contact) in a reversing motor starter control circuit?
In a reversing motor starter, an interlocking contact (typically an NC auxiliary contact from the forward contactor placed in the reverse coil circuit, and vice
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Question: What is the primary function of an interlocking contact (e.g., normally closed auxiliary contact) in a reversing motor starter control circuit?
Answer options:
- To provide overload protection for the motor
- To allow the motor to be stopped from multiple locations ✅ To prevent simultaneous energization of both forward and reverse contactors
- To provide a seal-in circuit for the 'start' button
Correct answer: To prevent simultaneous energization of both forward and reverse contactors
Explanation: In a reversing motor starter, an interlocking contact (typically an NC auxiliary contact from the forward contactor placed in the reverse coil circuit, and vice versa) is crucial for safety. It prevents both forward and reverse contactors from being energized at the same time, which would cause a direct short circuit if both main contactors closed simultaneously. Overload protection is handled by overload relays, multiple stop points by series NC contacts, and seal-in by parallel NO contacts.
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