Instantaneous Pickup
Instantaneous pickup is a short-time, no-intentional-delay overcurrent protection setting on a circuit breaker or protective relay that trips the device as fast as it can operate when current exceeds a defined threshold, typically to protect equipment from high fault currents like bolted short circuits and limit arc-flash energy.
On a manufacturing shop floor, instantaneous pickup settings on main and branch circuit breakers determine how fast major faults are cleared, limiting fault duration and arc-flash incident energy per CSA Z462/NFPA 70E. In motor control centers, instantaneous elements are tuned to allow normal inrush while clearing true faults, ensuring selective coordination. During arc-flash studies, these settings are critical inputs for time-current curves, affecting PPE categories. Compliance systems track settings per device, linking to coordination studies and arc-flash labels, with changes requiring engineering review to maintain WorkSafeBC/OHS compliance.
How is instantaneous pickup different from short-time pickup in breaker settings?
Instantaneous pickup triggers with no intentional delay, represented as a vertical line on TCC curves, used for severe faults. Short-time pickup has an adjustable time delay for selectivity in the 2-10x current range.
How do instantaneous pickup settings affect arc-flash incident energy calculations?
Lower instantaneous pickup reduces fault clearing time, lowering incident energy per IEEE 1584 and potentially reducing PPE category under CSA Z462/NFPA 70E, but must balance with selectivity.
What are typical ranges and constraints for instantaneous pickup on molded-case breakers?
Typical UL 489/CSA C22.2 breakers have instantaneous pickup adjustable from 5x to 10-15x continuous rating, with constraints to maintain listing and reliability; defeating the element requires engineered approval.