Characterizing Inrush Currents to Ensure Properly Sized Fuses
Application Notes
Application Brief
During the development of various technologies, many engineers encounter and must deal with inrush currents to their devices. This application brief addresses the reality of inrush current and the meaning of an I2t measurement, and then presents an actual I2t measurement and results from that measurement.
Many appliances draw a very large current for a brief period when they’re first switched on. This can cause problems in circuitry and hardware components. The shape and transient time of the inrush current depends on the particular device. Unless something is done to limit the magnitude of the inrush, a peak of 5 to 10 times the operating current would not be surprising. The reality of this large turn-on current makes it paramount to be able to measure and characterize the inrush in the development and verification of a device.