| Help please we are being given a a 50kW generator that puts out 3 phase
| 277-480 volt 3 phase, just have to pick it up. How do we use this with our
| sinle phase building? This is a serious question, if it cost too much then
| we will pass on the generator, so please help.
Whether or not this is practical depends on the design of the alternator.
Many generators are of the "12 lead" variety, meaning they have 6 windings
in the alternator. Others are of the "6 lead" variety and have 3 windings
in the alternator. Many have adjustable voltage controls.
The "12 lead" type would have 2 windings in each of the 3 phases that
can be wired in series or in parallel. In series, you can get from 220
to 277 volts. In parallel, you can get from 110 to 139 volts.
If this generator can be reconfigured by rewiring the terminals in the
main control box, it would be possible to arrange the connection to the
3 windings into what is known as a "double delta" configuration. This
is done by taking 1 each of the 3 phases and wiring them into a delta
arrangement (with the proper phasing to avoid a "short"). The other
winding of each of the three phases would also be wired the same way.
Now these two deltas are wired so that the 2 windings of ONE of the 3
phases is wired end to end, just like in series. You end up with a
configuration that graphically looks like (use Courier fixed font if
this does not display well):
/ \ /
/ \ /
Arranged this way, one phase (the one in series) will supply about half
the capacity. The other two phases will team up to supply the other
half of the capacity. Those other two phases will be running at a low
power factor of 0.5, so they will have an equally high current, but only
supplying a low amount of real power. The total capacity of a 50 kW
generator will then only 33.33 kW (2/3 of the three phase capacity).
The voltage regulator would normally be set higher (138.5 volts per
winding) for the 277/480 setup. It will have to be lowered to 120
volts for the 120/240 double-delta setup. That may lower the total
capacity depending on the kVA and/or current rating.
An experience generator technician or engineer would know if this one
can be reconfigured or not, and probably know how to do it if it can.
If you can tell us the exact make and model (should be in the nameplate)
someone may be able to be more specific. Also tell us how much power
you need out of the generator short-term and long-term.
Other options exist, but are more expensive. They include transformers
and dividing your building wiring three ways. Since you are being given
the generator, it sounds like any big expenses are probably not an option
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
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