The overload relay is used to protect motors in case of prolonged overload at what percentage of full-load current?

• A. Phase Unbalance
• B. Prolonged Overload (105 to 125% Full Load Current)
• C. Phase Loss
• D. Short Circuit

Answer: (B)

Overload protection in motors is about preventing overheating from running above the rated load for too long. A thermal overload relay senses sustained excess current and delays tripping long enough to tolerate normal startup and brief surges, but will trip if the excess current persists. This protection is typically set to allow about 105% to 125% of the full-load current, balancing the need to avoid nuisance trips with the need to prevent insulation damage from overheating. The other scenarios—phase unbalance, phase loss, or short circuits—are different fault conditions that are handled by other protective measures, not by this prolonged-overload setting.