INTEGRITY TESTING OF ISOLATION MEANS IN AN UNINTERRUPTIBLE POWER SUPPLY

摘要

The present invention provides an uninterruptible power supply wherein the isolation means is proactively and automatically tested during normal operation to ensure that it is capable of effectively isolating the input from an auxiliary power supply during emergency operation. The uninterruptible power supply includes an input for coupling to a main power supply, an output for connection to an electrical load, a rechargeable energy storage unit adapted to be charged from the main power supply and selective isolation unit configured to isolate the auxiliary power supply from the input during emergency operation. A first element establishes a reverse polarity across the isolation unit for a test period during normal operation, and a second unit monitors a voltage representative of an input voltage to the isolation unit and outputs an error signal if the monitored voltage remains or rises above a reference voltage during the test period.