Continuous duty motors with a marked service factor not less than 1.15 shall have the minimum running overload protection sized at ___ percent of the nameplate rating of the motor.

Continuous duty motors with a marked service factor not less than 1.15 shall have the minimum running overload protection sized at ___ percent of the nameplate rating of the motor.

• A. 125
• B. 115
• C. 130
• D. 140

Answer: (A)

Continuous duty motors that are designed to tolerate at least a 1.15 service factor can operate safely with some extra load beyond the nameplate rating. The running overload protection is sized to permit that extra load without tripping, while still protecting the motor from true overload. Setting the protection at 125% of the nameplate current provides enough margin to cover the service factor operating range and normal variations, without being so high that protection loses effectiveness. The other percentages either sit too close to the nameplate rating or provide more headroom than the standard practice requires, which is why 125% is the correct choice.

Continuous duty motors that are designed to tolerate at least a 1.15 service factor can operate safely with some extra load beyond the nameplate rating. The running overload protection is sized to permit that extra load without tripping, while still protecting the motor from true overload. Setting the protection at 125% of the nameplate current provides enough margin to cover the service factor operating range and normal variations, without being so high that protection loses effectiveness. The other percentages either sit too close to the nameplate rating or provide more headroom than the standard practice requires, which is why 125% is the correct choice.