A power supply that employes automatic switching of main power supply from primary to secondary (usually battery and/or diesel generator) upon failure of the primary.
A means of providing uninterrupted power to critical instrumentation for a limited period of time even in the event of a plant power failure. Usually accomplished by an inverter, transfer switch and batteries. Alternatives means may include motor generators.
A type of power supply that can provide electrical power even when line power is lost.
An iverter (AC from DC batteries) which provides a bumpless transition of power to the process control system in the event of plant power failure. the UPS will supply for a limited period (e.g., 15 minutes).