American Power Conversion MX28B2400, MX28B4800 manual DC Distribution, Battery Management

System Status and Alarm Reporting

The PSCU monitors system voltage using a high accuracy digital voltmeter attached to the system bus. The PSCU monitors system temperature using a temperature IC mounted in the PSCU. The PSCU monitors system current by summing the current reported by individual rectifiers. The PSCU reports a number of system alarms including system high/low voltage and high/low temperature. Refer to Section 5.6 for PSCU control functions.

5.4. DC Distribution

Distribution is included in each bay for up to 48 plug-in circuit breakers, a variety of bolt in breaker sizes or four telecom fuses. Circuit breaker bays with three rows of bolt in circuit breakers or fuse bays are also available. The plug-in circuit breakers can be 1 to 100 amps, with 60-100 amp breakers requiring two positions and a circuit breaker adapter kit. When a plug-in circuit breaker trips, a normally open switch closes and a CB alarm is reported by the PSCU. To disconnect a load attached to a circuit breaker, move the lever to the down “OFF” position. To disconnect a load attached to a telecom fuse pull the fuse holder straight out of the fuse holder base.

NOTE: Plug-in Circuit breaker alarm contacts close when the circuit breaker is tripped but not when it is turned OFF. Bolt-in Circuit breaker alarm contacts close when the circuit breaker is tripped or turned OFF.

5.5. Battery Management

Battery Charging and Protection

Battery charging and protection are integrated into the MX28B DC power system to support the primary function of providing power to the load. Accurate measurement of battery parameters like voltage, current and temperature are used to maintain and protect the batteries attached to the power plant.

Charging the battery at the correct rate reduces battery heating, increases the charge returned to the battery and prevents excess hydrogen generation or, in the case of VRLA batteries, possible thermal runaway. Battery Maximum Recharge Current is set to the appropriate rate, which is usually based on the size of the battery plant in Ampere-hours.

A typical recharge current setting is battery capacity (abbreviated as “C”) divided by number of charging hours. As an example, a “C/10” rate will basically return the battery to full charge in 10 hours. A C/8 rate is probably the highest current, which should be considered for charging under normal circumstances.

MX28B1200/2400 MX28B1200/4800 –48 VDC User’s Manual Page 34