TB9300 Installation and Operation Manual Installation 81
© Tait International Limited April 2024
4.6.3 Connecting DC Power
The PMU is designed to accept a nominal 12VDC, 24VDC or 48VDC
input (depending on the model) with negative or positive ground. There is
a minimum DC startup threshold to prevent damaging a battery which has
little capacity left.
You must connect the DC supply from the battery to the PMU via a fuse or
DC-rated circuit breaker with the appropriate rating, as shown in the table
below. Select a D curve circuit breaker with an interrupt capacity of 1000A
or more, and an inrush current capability of at least 500A for a minimum
of 3.5ms.
Notice The inrush current is not affected by the state of the DC mod-
ule on/off switch on the PMU. This switch does not disconnect power
from the DC converter itself. It disables the converter by switching off
its control circuitry. Even when the DC converter is off, the DC input is
still connected to its power circuitry.
The DC input leads should be of a suitable gauge to ensure less than 3%
voltage drop at maximum load over the required length of lead.
Terminate and insulate the DC input leads to protect them from
accidentally shorting to the subrack if the PMU is removed before the leads
are disconnected. Protective covers for the DC terminals are supplied with
each PMU. We recommend a screw torque of 18–20lbf·in (2–2.25N·m).
Nominal Supply
Voltage
Input Voltage
Range
Circuit Breaker/
Fuse Rating
a
a. The actual current consumption of the base station will be lower than these re-
quirements (refer to the Specifications Manual for more information).
Recommended
Wire Gauge
b
b. For a 3% voltage drop over 4.6m (15ft) at the expected maximum current.
12VDC 10VDC to 16.8VDC 60A 8AWG / 10mm
2
24VDC 20VDC to 33.6VDC 30A 10AWG / 6mm
2
48VDC 40VDC to 60VDC 15A 12AWG / 4mm
2
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