American Power Conversion MX28B400 Operation, Technical Description, Rectifier Management

4 Operation

4.1. Technical Description

The MX28B-400 Power System is designed to supply safe +24 Vdc primary power through the use of up to four rectifier modules. 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 1 A all the way to 100 A. Battery recharging, temperature compensation and low voltage disconnect are included. The controller can monitor up to 4 discrete external events with dry contact inputs.

4.2. Rectifier Management

AC Input Power

The basic component of the power system is the rectifier module, which rectifies utility ac into nominal +24 Vdc. Each rectifier module requires 176-264 Vac 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 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 4.6 for PSCU control functions.

MX28B400 +24 VDC User’s Manual Page 20