Question:
Crawling of a motor results from_______.
Crawling of a motor results from_______.
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Crawling is often caused by odd harmonics—primarily the 7th harmonic torque.
Updated On: Jun 24, 2025
- High load at the time of starting
- Low supply voltage
- Harmonics developed in the motor currents
- Short circuit condition in induction motor
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The Correct Option is C
Solution and Explanation
Step 1: What is crawling?
Crawling refers to the phenomenon where an induction motor runs at a speed significantly lower than synchronous speed (often around 1/7th of synchronous speed). Step 2: What causes it?
Due to harmonics in the supply current (especially 7th harmonic), a parasitic torque is produced at lower speed.
Step 3: Why harmonics cause this?
The 7th harmonic flux rotates in the same direction but at 1/7th the synchronous speed. If the torque produced at this speed becomes significant compared to the fundamental, the rotor may get "locked" at this speed.
Conclusion: Crawling is mainly due to harmonic components, particularly the 7th harmonic.
Crawling refers to the phenomenon where an induction motor runs at a speed significantly lower than synchronous speed (often around 1/7th of synchronous speed). Step 2: What causes it?
Due to harmonics in the supply current (especially 7th harmonic), a parasitic torque is produced at lower speed.
Step 3: Why harmonics cause this?
The 7th harmonic flux rotates in the same direction but at 1/7th the synchronous speed. If the torque produced at this speed becomes significant compared to the fundamental, the rotor may get "locked" at this speed.
Conclusion: Crawling is mainly due to harmonic components, particularly the 7th harmonic.
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