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Standby Application Solar Application Wind Application Telecom Application

Standby Application

A Standby Power Supply (SPS) is an AC back-up power source where the inverter only supplies the load when a brownout or blackout occurs. During normal operation the load is powered directly from the AC Utility, the inverter is not operating and the SPS is off-line from the load in standby mode. When a blackout or brownout occurs, the SPS senses the blackout or brownout condition, turns on the inverter and transfers the load to the inverter and battery through a transfer switch. These are sometimes referred to as a Standby UPS.

The Basic SPS has the following characteristics:

 The primary power source is supplied directly from the AC utility through a simple passive filter/surge suppresser, similar to a surge strip. It does not regenerate the output and provide continuous conditioning of the power to isolate the wide range of power problems on the AC utility line from the computer load.

 The actual transfer time will be several times slower than the ideal time if the input voltage is low or if the batteries are not fully charged at the time a blackout occurs. Also the computer power supply ride-through is greatly reduced when the input voltage is low because its own input capacitor is not charged up.

 When a blackout or brownout occurs, the inverter must start-up and takeover the load which causes sudden stress on the inverter and transmits switching transients to the load. The inverter is most vulnerable to fail and drop the load at the critical time when it is needed to take over the load.

 The output voltage is not regulated and will follow the input voltage variations, usually from 102 volts to 136 volts or higher which is a range of 34 volts (28%). At the lower limit, the SPS transfers to inverter and battery which uses up battery energy during brownouts. Some SPS units also transfer to inverter and battery at the upper limit.

In addition to the Basic Standby Power Supply, other variations of off-line SPS products include Standby With Boost and Standby-Ferro types.