On 05/04/2017 09:36 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.
Line current times voltage give you KVA per line. Then,
multiply by 1.732 to get total KVA. KW / .7457 give HP, not
counting losses or power factor. You don't actually need a
3-phase source, you only need to generate one new phase
(although if the 4331, etc. want 208, you probably don't
want to feed it 240 V). But, you DO need a true sine wave
source, and VFDs do not produce sine waves, they put out 400
V PWM waveforms that look fine to a motor, but not good at
all to electronic loads.
It is possible that a hefty used VFD with an appropriate
filter would turn it into a nice sine wave at lower cost.
For multiple KVA loads, that might be a more economical way
to go, if you don't mind creating such a filter. (Probably
be good to put a transformer between the VFD/filter and the
computers, so the line could be balanced around neutral, too.)
Jon
