PDU for high amp 48Vdc

For larger DC devices with ~50amps per side, does anyone have a software accessible way to turn off power?

I've looked into PDU's but the ones I find have a max of 10amps.

I've considered building something with solenoids or a rotary actuator that would turn the switches on or off, but that's a complete one-off and would need to be done for each device we manage (not to mention it involves janky wiring all over the place I've got to explain to the colo)

My use case is pretty infrequent so it needs to be remote-hands cheap.. it's for emergencies when you need to completely power cycle a redundantly powered DC device. The last time I needed this it was because a router was stuck in a boot loop due to a bad IOS upgrade and wouldn't break to rommon since it had been >60 seconds. It came up again tonight because we wanted to disable one power supply to troubleshoot something.

FWIW, I believe I've seen newer Cisco gear with high-end power supplies that have a console or ethernet port which would possibly let you shut them down remotely. That solves the problem nicely if you're dealing with only one bit of hardware, but I'd like a general solution that worked with any vendor. Possibly a fuse panel with solenoids that could add/remove fuses when needed.. or would that be considered dangerous in code-ways or in telco fire regulation ways?

We use ServerTech for -48Vdc switching, http://www.servertech.com/products/-48vdcpowermanagement/

Not quite remote-hands cheap, but worth every penny in a pinch.

The rotary actuators are an off-the-shelf item for transfer switches. No problem to get them paired with high-amperage switches. But a contactor, which is a solenoid-driven switch, is also an off-the-shelf item. The ones I use in EV applications are rated for 1000A, and cost about $300. You need to be careful to look at the trade-off between voltage, amperage, and the per-cycle probability of a weld, though. An over-rated contactor helps a lot if you're going to be cycling it a lot, whereas if it's for emergency use only, you can hew a lot closer to the max rating.


None of the stuff you'll make has UL or NEBS approval unless you pay
for that. I'd be inclined to suck it up and pay for remote hands to
turn a switch unless you own the colo or they're casual enough that
they don't care (your insurance company might though).

Should you decide to go ahead and build, be sure to check the DC
rating vs. AC rating for break under load - AC arcs are a lot more
self-extinguishing than DC arcs are. Consider a snubber (resistor and
capacitor in series across the contacts) in your design to minimize

More on AC vs DC here: http://www.temcoindustrialpower.com/product_selection.html?p=ac_vs_dc_contactor

For context, my Lincoln IM206 arc welder can be dialed down as low as
30 amps, and will have an open circuit voltage of way under 48 volts
when it's set that low (no, I don't feel motivated enough this early
in the morning to go fire it up and stick a voltmeter on it).


"Bill Woodcock" <woody@pch.net> writes: