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017-882-B0-001 Rev. E (06/2018)
1.0 Introduction, Continued
The optional AlphaDOC adds a second isolated
output to the power supply. It provides programmable current limits for
two output channels and protects system components by shutting down the load during overcurrent and short circuit
conditions. The AlphaDOC is similiar in function to the Programmable Interface Module (PIM) that is available for the XM2
Series.
The AlphaDOC has a programmable overcurrent threshold (3A-25A) and overcurrent tolerance period that specifies the
time (20-9900ms) an overcurrent condition is permitted before shutting down.
The programmable retry limit can be programmed to select how many times (0-40) after a programmable delay (5-301
seconds) the AlphaDOC will attempt to reconnect an output once it has been shut down. When the limit is reached, the
XM3 power supply automatically retries once every 30 minutes until the fault clears.
Adding the AlphaDOC to the power supply provides these advantages:
A second isolated output:
The main purpose of the AlphaDOC is to limit the impact of a fault condition in one output
channel. If a fault condition occurs in a power supply (without the optional AlphaDOC installed) the entire customer
network can be affected. The AlphaDOC option affords protection to one output should a fault condition exist on the
other. This gives you flexibility to isolate Output 1 from Output 2.
A current for critical loads:
With the AlphaDOC option, you can designate one output as the primary connection
and the other output as the secondary connection. Commonly, critical loads are connected to Output 1 as the primary
feeder. Using the overcurrent limit settings, you can ensure the primary output always provides the necessary power.
For example, on a 15 Amp power supply, if a customer needs 10 Amps available on Output 1, the overcurrent limit
for Output 2 is set at 5 Amps, so regardless of Output 2, 10 Amps will remain available for the primary Output 1.
Additional current protection:
The standard power supply current limit protection is provided by the fold-back
characteristics of the transformer (150% of rated output). The 150% current limit may exceed the ratings of active
devices in the cable network and cause failures. You can lower the maximum current provided at each output by
lowering the overcurrent limit of each respective output. Therefore, to minimize failures due to excess current supply,
set the overcurrent limit to a value below the maximum current the active components can tolerate.
For example, on a 18A power supply, where both outputs are programmed to 10A maximum and both outputs are
supplying 10A, neither output is “in violation” but the total system at 18A is operating at 111% of its rated output. In this
example, after 30 minutes, the power supply will begin a “load shedding” algorithm. The first action is to disconnect Output
2. If this does not correct the system overload, the next action is to disconnect Output 1.
1.3.3 AlphaDOC (Dual Output Controller)
Table 1-3, Duration of Load
The table below depicts a condition in which no DOC is installed, or no individual output is above its trip setting.
NOTICE
:
Power Supply Load
Duration
918 and 918D
All Other Models
Permitted Duration of Load
>125%
>150%
30 seconds
113% to 125%
125% to 150%
10 minutes
108% to 113%
115% to 125%
30 minutes
<108%
<115%
Several months
