On 05/04/2017 10:36 AM, Guy Sotomayor Jr via cctalk wrote:
On May 4, 2017, at 8:04 AM, jim stephens via cctalk <cctalk@classiccmp.org>
wrote:
On 5/4/2017 7:36 AM, Guy Sotomayor Jr via cctalk wrote:
Does anyone know how to convert KVa to 208v 3-phase currents and/or HP? IBM’s
docs all specify power in KVa and most of the 3 phase converters (other than
what Bob posted) seem to specify HP. If I’m going to spend serious coin on a
phase converter (I think I found it online for ~$3k…ouch!), I want to make sure
it’s sized properly.
Thanks.
TTFN - Guy
You will also need to get the motor start information, or you will vaporize a
phase converter.
Another possible approach that a friend is taking is to take three single phase
identical UPS system and synch the phases of the three converter output
circuits to proper three phase.
He's made up one from three junk APC units I've got. I can forward info if you
would like on this approach from him. One thing that helps is he snagged and
maintained the drawings of all of the APC and other output circuits over the
years and has good info on how to pull this off.
The quadrature power will be something to deal with on your three phase loads,
but you may be able to run quite a bit of single phase hardware directly off of
the mains.
OK, that’s not helping. Here’s what I have (from IBM site planning docs
GC22-7064-10 and GC22-7069-2):
3340-A2 DASD: 2.2 kVA 3-phase
3340-B2 DASD: 1.7 kVA 3-phase (powered from 3340-A2)
3803 Tape Control unit: 1.8 kVA 3-phase
3420 Tape drive: 2.9 kVA 3-phase (powered from 3803) (x2)
2821 control unit: 1.4 kVA 3-phase
1403N1 Printer: 1.5 kVA 3-phase (powered from 2821)
2540 card reader/punch: 1.2 kVA 3-phase (powered from 2821)
So I have 3 potential power feeds:
DASD: 3.9 kVA
Tape: 10.5 kVA
I/O: 4.1 kVA
For a total of 18.5 kVA
So the several $1000 question is how do the kVA’s map into 208v 3-phase amps?
18.5 KVA /208 = 88.94
88.94 / 1.732 = 51 A
Since this is given as KVA, it should include the power factor.
Depending upon how that works out I need to figure out if 2/3 converters
make sense or just one big one.
My simple minded conversion is to take the 18.5kVA, multiply by 1000 and divide
by 208. That gives me just shy of 90A. Do I then divide by 3 to get A/phase?
If so, then it’s 30A per phase which seems reasonable. But I don’t know if
that’s the correct formulation.
It isn't. See above. A lot of this is circulating current,
so the real power draw from the mains will be less. Still,
most likely over 10 real-power KW from your 240 V
single-phase mains.
Jon
Jon
