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 an illustration of how the switch happens 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.
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.
Source A
Source A
Source A
Source B
Source B
Source B
Attached
Equipment
Attached
Equipment
Attached
Equipment