Inrush current control for equipment powered by UPSs

With the present-day widespread use of uninterruptible power supplies (UPS) in power equipment, inrush becomes a major concern since most UPSs have a limited ability to furnish high peak-current demands. The author discusses inrush current in general and presents, both conceptually and in block-diagram form, a proposal for circuitry that manages and eliminates the inductive inrush current concerns. It is established that the most important factor in identifying the influence on the UPS of a power supply connected to the UPS is the crest factor of the applied load. To control the inrush current, the preferred approach for a capacitive load is to switch a current-limited resistor temporarily into the circuit, while for an inductive load, a well-chosen critical turn-on angle of the connecting device is the most effective method.<>