Battery Calculation; Topology; Operating Conditions - Bosch PRAESENSA Installation Manual

PRAESENSA
The peaks are at -1.3 dBFS (= 0.86 of full scale) and the RMS level is at -9.4 dBFS (= 0.34 of
full scale). Both these levels are also visible in the level bar at the top.
5.4

Battery calculation

The PRAESENSA system includes multifunction power supplies, like the PRA-MPS3, to power
other PRAESENSA devices from the mains, but also from a battery in case of mains failures.
PRAESENSA encourages to use a distributed system approach, in order to minimize expensive
(fire resistant) loudspeaker cabling, therefore each multifunction power supply uses its own
battery. There is no large battery set that supplies power to a centralized system on one
location.
5.4.1

Topology

Each PRA-MPS3 multifunction power supply has the capability to power up to three amplifiers
via 48 VDC, one system controller (or other device) via 24 VDC and one Call station via PoE. A
single 12 V battery is charged by the multifunction power supply to which it is connected. This
battery serves as a backup power source during mains failures. A large system with dozens of
amplifiers will contain many PRA-MPS3 devices, each having its own battery. This means that
the required capacity of each battery must be calculated separately for the PRA-MPS3 it is
connected to, taking the load into account that is served by this specific PRA-MPS3.
For the devices that are powered from a PRA-MPS3, it is important to notice that the power
consumption of each device may vary depending on operation modes and how it is connected.
When the power consumption has been calculated or measured, the corresponding battery
current draw (in case of a mains failure) can be calculated or measured. The power taken from
the battery will always be slightly higher than the power that is consumed by the device,
because of additional losses in the DC/DC converters inside the PRA-MPS3 that convert the
battery voltage to 48 VDC and 24 VDC.
5.4.2

Operating conditions

PRA-SCL
The power consumption of the PRA-SCL is relatively small, stable and hardly affected by
system activities. It is powered from the 24 VDC output of the PRA-MPS3. Only the number of
active Ethernet ports increases the power consumption. At least one port will be in use, but
often more ports are active. In case of a connection to a PC for logging and to two
independent loops for linking to other PRAESENSA devices, all five ports will be in use.
Bosch Security Systems B.V. Installation manual
System composition | en
2019.11 | V1.00 |
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