Looking for Parallel UPS Solution - HELP!

[Aaron407]

Hopefully someone can help me, I've spent hours searching the internet
for a solution to no avail. I'm looking for Uninterruptible Power
Supplies that can be connected in parallel for best redundancy to
protect a DCS panel. I'm aware that there are many UPSs that support
the N+1 or N+X systems for the power cells, but still use only a single
controller. However, we've seen problems in the past where the
controllers malfunction on a UPS and, as a result, it failed to back up
the systems regardless of any redundant power cells. Therefore, two
distinct systems (with separate controllers) with the ability to be
connected in parallel (ie. 1+1 setup) is definitely the setup I'm
looking for, but, as expected, their outputs need to be phase locked.
Specifics of what I'm looking for are as follows:

Input: 120V AC or 208V AC, 60Hz (common supply to both units)
Output: 120V AC, 60Hz
Power: 2300W < Output Power < 3300W (for each unit)
Mount: preferably tower/floor standing, but 19" rack mount if nothing
else is ok.
Electrical bypass: preferable for maintenance and replacement of UPSs

If there are no UPS systems specifically designed for this setup, is
there any kind of interface that can be used to phase lock the
individual outputs of two identical UPS units?

I'm hoping someone can help me in my search. Any help at all would be
greatly, greatly appreciated.

-407

 

[[email protected]]

Input: 120V AC or 208V AC, 60Hz (common supply to both units)

Output: 120V AC, 60Hz
Power: 2300W < Output Power < 3300W (for each unit)
Mount: preferably tower/floor standing, but 19" rack mount if nothing
else is ok.
Electrical bypass: preferable for maintenance and replacement of UPSs

If there are no UPS systems specifically designed for this setup, is
there any kind of interface that can be used to phase lock the
individual outputs of two identical UPS units?

For this to work. The ups's got to have phase synchronisation interface
implemented. Or be modified to have it. I suspect you will have to ask some
specialised ups reseller for this option.

On the lowlevel the output stage(s) got to accept external clock.
There's another more sinister option. Have common clock "bus" that makes the
upses converge on a common frequency.
Wonder how the power companys do this..

Another option is to skip the AC alltogether and do like telco operators do.
Use 48V DC for distribution. And switched powersupplies to supply power to
any equipment. 48V = 4 pieces of 12V Battery. And just below the highvoltage
legalities. With DC backup solutions become so much easier.

120V AC -- AC/DC -- Batteries --------48V rail-----------------------
DC/DC DC/DC DC/DC DC/DC
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