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POWERING TECHNOLOGY

Manual No. MS0027-MAN rev. 4

guardian_access_3u_ms27-man-rev4-0817.indd

The Guardian Access 3U is capable of delivering up to 14.7kW steady state power to the

combined load and batteries. The maximum power available to the load is 10.7kW. The

system is based on hot-swappable 48V rectier modules which are working in parallel with

automatic load sharing.

The power system is normally congured with N+1 redundancy, with N as the number

of rectier modules necessary for feeding the load and charging the battery and 1 as the

redundant rectier module. In normal operation the rectier modules are used to feed the

load and simultaneously maintain the batteries in a fully charged state.

Once the mains input power is failed, the rectiers are shut down and the batteries feed

the load immediately. If the battery voltage drops below a preset level, the Low Voltage

Disconnection (LVD) circuit disconnects the batteries automatically to prevent over-discharge

of the battery to prolong battery life. When the mains input power is restored, the rectiers

will start up automatically to feed the load, close LVD circuit and recharge the batteries.

System performance is supervised and controlled by the controller, PCC or ACC Extended.

The DC output voltage, alarm thresholds, LVD circuit operation, temperature compensated

battery charging can be set by the controller. Any malfunction will be indicated by LED, text

in the display and operation of dry contacts.

However, the system controller is not a single point of failure. In the event of controller

malfunction, basic tasks like feeding the load and charging batteries will be maintained by

the rectier modules directly at preset default values.

The alarm and threshold setting of the power system can be set either through the buttons

and operation menu on the local controller, or remotely through the PowCom™ supervision

software.

Battery Breaker

Battery

LVBD

Load Breakers

DC Distribution

Rectifier

Controller

Figure 2-2 Principal of Operation

Unipower Guardian Access 3U User Manual

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