User Manual

Rack ATS AP44xx User Manual4
2. The ATS constantly monitors the quality and amount of power coming from sources A and B. If
one source begins to supply power that does not meet your settings, the ATS will disqualify that
source.
a. If the disqualified source is not in use, the ATS will generate an alarm to indicate that
redundancy has been lost.
b. If the disqualified source is in use, the ATS will switch to draw power from the other
available source.
If a preferred source is set, the ATS will wait 30 seconds to monitor that source. After 30 seconds,
if the preferred source becomes usable again, the ATS will switch back to the preferred source.
See how the switch happens in the illustration below.
NOTE: The entire switching process (described in step 2) takes a maximum of
10 milliseconds (ms) at high sensitivity, and 12 ms at low sensitivity. (This applies to both 50 Hz
and 60 Hz sources.)
pdu0776a
Source A
Source B
Attached Equipment
Source A
Source B
Attached Equipment
Source A
Source B
Attached Equipment
Source A is providing power to the attached equipment, while Source B is isolated from
the attached equipment.
Firmware detects that Source A is out of the user-specified transfer range. The input
power from Source A is removed by disengaging the relays. (This allows for
out-of-phase switching and significantly reduces the opportunity for relay welding.)
Source B relays are engaged; Source B provides power to the attached equipment.