TB9400 Installation and Operation Manual Installation 73© Tait Limited March 20174.6.3 Connecting DC PowerThe PMU is designed to accept a nominal 12VDC, 24VDC or 48VDCinput (depending on the model) with negative or positive ground. There isa minimum DC startup threshold to prevent damaging a battery which haslittle capacity left.You must connect the DC supply from the battery to the PMU via a fuse orDC-rated circuit breaker with the appropriate rating, as shown in the tablebelow. The circuit breaker must have a contact separation of 3mm, aninterrupt capacity of 1000A or more, and an inrush current capability of atleast 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 powerfrom the DC converter itself. It disables the converter by switching offits control circuitry. Even when the DC converter is off, the DC input isstill connected to its power circuitry.The DC input leads should be of a suitable gauge to ensure less than 0.2Vdrop at maximum load over the required length of lead.Terminate and insulate the DC input leads to protect them fromaccidentally shorting to the subrack if the PMU is removed before the leadsare disconnected. Protective covers for the DC terminals are supplied witheach PMU. We recommend a screw torque of 18–20lbf·in (2–2.25N·m).Nominal SupplyVoltageInput VoltageRangeCircuit Breaker/Fuse Ratingaa. The actual current consumption of the base station will be lower than these re-quirements (refer to the Specifications Manual for more information).RecommendedWire Gaugebb. For a length of 5ft to 6.5ft (1.5m to 2m) (typical).12VDC 10VDC to 16.8VDC 60A 2AWG / 35mm224VDC 20VDC to 33.6VDC 30A 5AWG / 16mm248VDC 40VDC to 60VDC 15A 8AWG / 8mm2
