Abstract: A circuit breaker trip unit includes an input section receiving a phase current level signal. A processor is in communication with the input section and generates a first trip signal based on the phase current level signal and user-adjustable trip settings. The trip settings include long time and short time pickup and delay settings. An analog instantaneous trip circuit is in communication with both of the input section and the processor. The analog instantaneous trip circuit includes a digital potentiometer having a non-volatile memory. The potentiometer provides a reference signal corresponding to a resistance setting stored in the memory. The analog instantaneous trip circuit compares the phase current level and reference signals, and generates a second trip signal based on a result of the comparing. The processor programs the resistance setting stored in the memory according to a user-adjustable instantaneous current pickup setting.

Abstract: A circuit breaker electronic trip unit includes a controller, and a memory that stores a threshold tripping duration. The memory is readable by the controller. The trip unit includes a trip signal output, and an input section that receives at least one of a phase current level signal, a phase or line voltage level signal, and a contact state change signal. The trip unit activates the trip signal output and monitors the input section for a predetermined signal change. The trip unit determines a tripping duration from a timing of the activation of the trip signal output and a timing of the predetermined signal change. The trip unit compares the tripping duration to the threshold tripping duration to determine a sluggish circuit breaker operation.