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Page 24 MX28B200/400 –48 VDC User’s Manual (990-9133)
4.3. System Management
System Output Capacity
The power plant has two basic configurations:
The MX28B-200 supplies a maximum of 200 amps or 150 amps with N+1 redundancy.
The housing for this configuration provides space for one rectifier shelf that can hold up
to four rectifiers, a control unit, and one tier of up to 24 distribution circuit breakers.
The MX28B-400 supplies a maximum of 400 amps or 350 amps with N+1 redundancy.
The housing for this configuration provides space for two rectifier shelves that can hold
up to four rectifiers each, a control unit, and one tier of up to 24 distribution circuit
breakers. The differences between the 200 and 400 amp units are the exterior housing,
50-conductor ribbon cable and an additional rectifier shelf; all other parts are the same for
both configurations.
System Voltage Control
The PSCU monitors and adjusts the system voltage. It uses a voltage trim input to the
rectifier to precisely control the DC output voltage. In the event of PSCU removal or
failure, the shelf rectifier controller card will control the voltage at a programmed default
level. In the event of shelf rectifier controller card failure, the individual rectifiers will
default to the analog voltage level preset with the front panel “float’ adjustment pots.
System Current
The PSCU monitors individual rectifier currents and displays total system current as a
sum of rectifier currents. Load current can be found by adding battery current to system
current. Battery Current is positive when the battery is discharging.
Sys Current + Batt current = Load Current
For example, if the battery is charging the Batt Current reading could be (–) 40 A, Sys
Current reading could be 120 A. Load Current would be:
Sys Current + Batt current = Load Current
120A + (-) 40 A = 80 Amps.
If the battery is discharging the Batt Current reading would be 40 A, Sys Current would
reading would be 40 A. Load voltage would be:
Sys Current + Batt current = Load Current
40A + 40 A = 80 Amps.