Overview
A telecom or a datacom rack runs continuously for years, so its power system must be efficient, reliable and compliant, and it must derive several board rails from a common feed. COSEL provides higher-power 1U supplies, isolated DC-DC converters and EMI filters for the rack, and BeiLuo supplies them with genuine traceability and FAE support. This page shows how the parts fit together in a telecom and datacom power design.
The Rack Feed
The rack feed converts the mains into a bus, usually 24 V or 48 V, that the boards share. A COSEL PBA series supply such as the PBA600F-24 gives a 600 W 24 V output with active power-factor correction in a 1U chassis, and its efficiency and the active PFC keep the input current within the harmonic limit. The unit cools by a built-in fan, so the rack provides an airflow path and a filter, and the derating is confirmed at the highest ambient. A higher-power supply reduces the number of units and simplifies the rack wiring.
Active PFC and the Harmonics
A rack that draws a large current from the mains must meet the harmonic limit, so the active power-factor correction in a COSEL supply keeps the input current close to a sine wave and within the standard. This avoids a bulky external PFC stage and keeps the rack compact.
The Board Rails
Each board derives its own rails from the bus with an isolated DC-DC converter, so the board is protected from the bus and the ground loop is broken. A COSEL CBS series open-frame converter such as the CBS1002405 gives an isolated 5 V rail at about 100 W, and a small ZUS series converter gives a lower-power isolated rail for an interface or a sensor. Because the converters are compact and board-mount, several fit on one board, so a single 24 V feed serves the whole card.
Distributed Power Architecture
The distributed approach, one bus and a converter per rail, is common in a telecom rack because it keeps the current low on the bus, isolates the boards from each other and lets each board be tested on its own. The converter is the building block, and the isolation and the layout decide the noise and the reliability.
The EMI Filter
The rack input must meet the conducted-emissions limit, so a COSEL EMI filter sits between the mains and the supply. For a higher-current rack the NAC-30-472 gives a 30 A single-phase filter with screw terminals and a DIN-rail option, and the capacitor code sets the leakage. Choose the current above the load, mount the filter close to the input connector and bond the case to the chassis.
Installation and Grounding
A filter is only as good as its grounding, so bond the case to the chassis, keep the input and output wiring separated and keep the filter close to the connector. In a rack, plan the input wiring and the filter placement as part of the power design, not as an afterthought.
Reliability and Verification
A rack that runs continuously for years needs a good thermal margin and quality parts, so the supply is chosen with the derating and the airflow in mind and the converters are chosen for their isolation and their life. Validate the design on the bench by measuring the efficiency and the derating at the worst case, the ripple on each rail and the conducted emissions with the real load. Our FAE team can review the measurements and the layout.
Getting Help
Send your bus voltage, the current on each rail, the input and the environment to our FAE team, and we will propose a supply, the converters and a filter, help size the feed and the rails and review the cooling and the EMC. BeiLuo holds mainstream COSEL parts in regional stock and ships them with an import declaration, a certificate of origin and a RoHS compliance file, so a telecom power design can move from prototype to production without a supply gap.