Static Transfer Switches (STS) are essential components in data center power system configurations. Mainly relying on transformers primary side switching, these devices are the bridge between the power sources and the power distribution units. This architecture offers many advantages to the customer in terms of smaller footprint and lower costs; however, if not properly switched high transient inrush in downstream transformers will occur.
The inrush currents produced degrade the power quality of the preferred source, overload upstream UPS’s and trip protective circuit breakers.
The inrush currents can also create intolerable forces in the windings, which in turn reduce the lifecycle of power transformers as these currents can reach the short circuit rated value and can last many cycles before they dissipate.
This white paper by ABB will explain the saturation phenomena in detail, derive appropriate equations to understand this behavior and present a state of the art method used by the SuperSwitch®4, static transfer switch, to successfully eliminate and limit the inrush should a transfer be needed.