For a motor with a service factor greater than 1.0, how is the overload device typically rated?

When determining the appropriate rating for the overload device for a motor that has a service factor greater than 1.0, it's important to cite the overload device rating to provide adequate protection without nuisance tripping.

In this case, the correct answer states that the overload device should be rated at no more than 125% of the motor's nameplate full-load current rating. This approach is generally accepted because it allows for the additional capacity that the service factor provides. The service factor indicates how much overload the motor can handle safely, meaning that it can sustain more than its rated full-load current for a short duration without sustaining damage.

Setting the overload at 125% of the nameplate rating effectively accounts for the added strength of the motor due to this service factor, ensuring that the overload does not trip during normal but slightly heavy operation while still protecting the motor from prolonged overload conditions. This balance is key to effective motor operation and safety.

Other choices typically suggest higher percentages that may not align with safe operational practices, either risking motor damage or nuisance tripping of the device, which isn't practical for motor longevity and normal operating conditions.