For a continuous-duty motor with service factor 1.15 and more than one horsepower, the separate motor overload device must trip or be rated at no more than what percent of the motor nameplate full-load current rating?

For a continuous-duty motor with service factor 1.15 and more than one horsepower, the separate motor overload device must trip or be rated at no more than what percent of the motor nameplate full-load current rating?

• A. 100
• B. 110
• C. 125
• D. 150

Answer: (C)

Overload protection is meant to limit winding heating from extended overloads while tolerating brief overloads such as startup. For a continuous‑duty motor with a service factor of 1.15 and more than one horsepower, the separate motor overload device should be set to trip at, or be rated at, no more than 125% of the motor’s nameplate full‑load current. This 125% margin allows normal startup inrush and short-term overloads without nuisance trips, yet remains protective against sustained overload that could overheat the motor. A 100% setting would trip too soon during normal operation, 110% isn’t the standard protective setting for this case, and 150% would permit excessive current before protection activates, risking damage.

Overload protection is meant to limit winding heating from extended overloads while tolerating brief overloads such as startup. For a continuous‑duty motor with a service factor of 1.15 and more than one horsepower, the separate motor overload device should be set to trip at, or be rated at, no more than 125% of the motor’s nameplate full‑load current. This 125% margin allows normal startup inrush and short-term overloads without nuisance trips, yet remains protective against sustained overload that could overheat the motor. A 100% setting would trip too soon during normal operation, 110% isn’t the standard protective setting for this case, and 150% would permit excessive current before protection activates, risking damage.