What is the pickup tolerance when performing an instantaneous pickup test on a molded-case circuit breaker with an adjustable trip?

When performing an instantaneous pickup test on a molded-case circuit breaker that has an adjustable trip, the standard tolerance for the pickup setting needs to be understood in terms of electrical safety and functionality. The correct answer reflects the typical industry standard for these types of tests, which defines acceptable tolerances for the current at which the breaker operates instantaneously.

The correct tolerance of +40% and -30% signifies that the breaker should operate and trip within this range of the set current value. For example, if the adjustable trip setting is at a certain level, the breaker needs to trip when a fault current that is 40% above the set value is applied, and it should not trip if the current reduces to 30% below that value. This range is designed to ensure that the protective device operates effectively under fault conditions while still allowing for some flexibility in the operational parameters of the circuit breaker.

Other choices propose different percentages that do not align with industry testing standards for molded-case circuit breakers. Therefore, the significance of these percentages is crucial for ensuring reliable and safe electrical system operations, and the tolerance provided in the correct choice is a reflection of that industry norm.