Q

Powering modems with SMPS-based power supplies

Data center physical infrastructure expert Robert McFarlane discusses SMPS-based power.

I have to connect 22 modems in my data center with RAS. All these modems are equipped with transformer-based stepdown power supply 220V AC to 12V DC.

Should I use individual power supplies for all 22 modems or get SMPS-based consolidated power supplies? I hear that data center experts are recommending the SMPS-based supply.

We definitely need custom-made PDUs to connect these 22 adapters in rack.

There's a measure of reliability that comes with powering separately. But with your quantity of modems, as with other devices that use low-voltage transformer power, the wiring and receptacle requirements of this multiplicity can become overwhelming. If all these modems feed a single RAS, then the single SMPS modem supply and the single Remote Access Server are both potential single points of failure. If the modems are split to more than one RAS, I would suggest a commensurate number of modem power supplies.

I would also suggest that you pursue dual power cording for both the server and the modem power supplies if you are set up to provide dual power feeds to your equipment. Incidentally, there are Wiremold plug strips as well as more sophisticated cabinet power strips that are designed with transformer spacing. It should not be necessary to purchase custom devices if you choose to stay with transformers.

This was first published in October 2007

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