Okay, group. Stupid question.
I have a couple of racks of specialized equipment that need to be
hooked up to UPSs. The UPSs are the simple off-line kind. The line
voltage is 120, 60 Hz. The load is about 6 amps each, on two 20 A
circuits.
The power supplies inside these specialized boxes produce unwanted
harmonics (3rd, 5th, ... 17th, 19th, etc). It's about 12% THD. The
UPSs that I have do not accept them as being a valid load and kick
over to battery power immediately... even placing the UPSs on separate
circuits within that room doesn't help. Once all of the load is on
UPS, then they will kick off, in any combination of load, circuit,
UPS, etc. Once you get everything plugged in, the harmonics build on
each other and the UPSskeel over and die. The power supplies inside
these specialized boxes are apparently pretty noisy.
We can't buy new UPSs. No budget.
The electrician took his $4000 power analyzer to get the above
readings.
We need to design a filter to be placed inline between the load and
the UPS.
It needs to be able to supply peak 20 A, 120 VAC, with a good
rejection filter above 60 Hz. In other words, pass 60 Hz and filter
everything above it. I would like to keep the parts count low, and
definitely not introduce any other artifacts, like over damping, under
damping, etc.
I know next to nothing about filter design except that it will
probably involve a large coil (L) and a capacitor (C).
Can anyone point me in the right direction? Pretty please?
Bob the Tomato
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