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MX28B1200/2400 MX28B1200/4800 –48 VDC User’s Manual Page 32
5 Operation
5.1. Technical Description
The MX28B-1200/2400 Power System is designed to supply safe –54 VDC primary power
through the use of up to 24 rectifier modules. One rectifier bay may be added to increase the
capacity to 48 rectifiers. The MX28B-1200/4800 Power System is designed to supply safe –54
VDC primary power through the use of up to 24 rectifier modules. Three rectifier bays may be
added to increase the capacity to 96 rectifiers. In conjunction with an external battery string, it
will supply backup power as well. The Power System Control Unit (PSCU) will monitor all
MX28B functions and provides battery management including controlled battery recharge with
temperature compensation and low voltage disconnect. Integrated DC output distribution
supports loads ranging from ¼ Amp all the way to 700 Amps. Battery recharging, temperature
compensation and low voltage disconnect are included. The controller can monitor up to 4
discrete external events with dry contact inputs.
5.2. Rectifier Management
AC Input Power
The basic component of the power system is the rectifier module, which rectifies utility AC into
nominal 48 Volts DC. Each rectifier module requires 208/220/240V AC (MRF28H54BV), or 277V
ac (MRF28H54BV50) single-phase, 50/60 Hz. A breaker installed in a remote panel should
individually protect each rectifier circuit.
DC Output Power
The DC outputs of all the rectifiers in the system are connected to a common bus that is rated to
carry the current of the entire system. The rectifier modules will equally share the entire load,
independent of the PSCU. The rectifiers will continue to provide DC power if the PSCU is
removed or fails.
Rectifier alarms reporting
The rectifier has numerous sensors inside the unit that monitor fan fail, high temperature,
high/low voltage, etc. These rectifier sensors trigger outputs that are monitored by the PSCU.
In addition rectifier current is measured inside each rectifier. The PSCU can trigger output
relays in the event of a rectifier alarm. Refer to Section 5.6 for PSCU control functions.