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What is the minimum required trip setting for the overload device when protecting continuous duty motors?

  1. 110 percent

  2. 120 percent

  3. 125 percent

  4. 140 percent

The correct answer is: 125 percent

The minimum required trip setting for overload devices protecting continuous duty motors is established based on the motor's full-load current rating and the need to prevent nuisance tripping while still ensuring adequate protection. Setting the trip point at 125 percent of the motor's full-load current rating allows for a reasonable safety margin. This percentage takes into account the normal variations in motor operation during continuous duty cycles, such as starting torque, temporarily elevated current, and potential overload conditions, while providing enough time for the motor to handle brief instances of overload without tripping the device. Setting the trip at 125 percent ensures that the overload device will actuate only in the case of significant motor issues, such as sustained overloads which could lead to damage. This balance helps to maintain efficient operation and minimizes downtime, which is particularly important in continuous duty applications where motors are frequently running for extended periods.