What causes a Current Surge?

A current surge typically occurs in response to an inrush of electricity when electrical devices are initially turned on. This phenomenon is characterized by a momentary spike in current drawn by the device as it starts up, particularly for motors and transformers. During this start-up phase, the device requires more current than it will during normal operation as it overcomes initial inertia and internal resistance, leading to a temporary increase in current beyond the usual operating level.

This is primarily because many electrical devices, especially those with inductive loads like motors, have a much higher current draw when they first start up compared to their running state. Understanding this surge is critical for designing electrical systems and selecting appropriate protective devices to prevent damage from these brief spikes in current. This knowledge is essential for managing circuit capacity and ensuring the reliability and safety of electrical installations.