CommScope CMC-21 - Battery Voltage and Battery Supply Resistance

Material ID 860647713
Rev B, V.05, February 2022
Page 31
38 Pages
► Battery Voltage and Battery Supply Resistance
Nominal battery system circuit voltage, float (charging) voltage, and battery supply resistance is in
accordance with PS-E.1.6.100.1 where the:
■ Nominal battery system circuit voltage is -48 VDC
■ Nominal float (charging) voltage is -54.5 VDC
■ Total battery supply resistance of all battery strings is 5.33 Ohms
Use the information in this section to calculate the maximum short circuit current in the final installation.
Caution:
— The design of this equipment allows it to connect to a battery source of nominal 48 VDC based
on 2 V per cell with a minimum resistance of 0.5 mΩ.
— This resistance calculation includes the minimum battery system equivalent parallel resistance
and the interconnecting conductors to the input termination point of this equipment.
— Use these values to verify you do not exceed the DC short circuit current withstand rating of the
equipment and that the overcurrent protection devices have the required interrupting capability.
— Field installed or replaceable components that intentionally interrupt output short circuit current
shall have a specified interrupt rating of 10 kA.
► Battery System Resistance and Short Circuit Current Calculation
To calculate the battery system resistance and short circuit current for this cabinet as given in
PS-E.1.6.100.1 of IEC61204-7 use the following:
■ Battery String Resistance Calculation (per string)
R
Str1
= (4 x R
b
) + (3 X R
bc
) + R
sc-
+ R
sc+
Where:
R
b
- Battery resistance
R
bc
- Resistance of battery links
R
sc-
- Negative string cable
R
sc+
- Positive string cable
■ Total Resistance of All Strings
R
Tstr
=
1
(R/R
str1
) + (R/R
str2
) + (R/R
str3
)
And:
SCCR =
V
Batt Supply
R
Tstr