Aligning phases using PFC (was RE: Getting more input power)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ian McLean" <ianmm-at-optusnet-dot-com.au> 

This has been an interesting thread.    I never realised just how many
options and confusion that creates for folks in the US ...  I am glad I
started it even though my questions were answered awhile back.

It is however a little simpler in NSW Australia, partially because we do not
have the 110VAC to confuse the issue further.

Putting aside industrial application and rural distribution, which always
complicate the issue, suburban houses here get one, two, or three phases
from the 3 phase power lines (4 wires).  The 3-phase is 415VAC across
phases, and 240VAC between each phase and neutral.  The phases are 120
degrees apart from each other.  The mains frequency is 50Hz.

This is stepped down using 3 phase pigs either in big green boxes (no
telegraph poles in newer suburbs), or on the poles in older suburbs, from
various 3 phase outputs available depending on the local substation.  22kV
and 33kV 3-phase from the substation are common.  The pigs are usually big
ones (50-75kVA+) and power a number of houses.  I agree though, with someone
on this list, along time ago in a galaxy far, far away, that it would be
better to have a smaller pig, 5, 10 or 20kVA for each house.  This way,
power dips during the hottest parts of summer and peak hours would be
minimized.

If the suburb is an older one, 2 or 3 phases to a house is common, newer
houses generally have 1 phase unless more are needed.  We have all 3 to our
house, but we need it for the ducted air conditioning (3 phase motors),
which is 5 horses (fantastic in summer I must say ;) )  Power outlets and
power to house is balanced between phases, i.e. some outlets on each phase.

If I get a 3-phase 50A outlet, which for me is as simple as running a line
from my distribution box to my workshop with an RCB breaker in the box and a
3 phase (4 pin) outlet in my workshop, it would be a simple Wye connection
(3 actives (hots) and 1 common neutral).  I can take 1, 2 or, 3 50A single
phases using each hot with neutral common.  If I want single phase 415VAC I
can use 2 hots and omit the neutral.  I can use all 3 phases to run 3 phase
equipment, and I can do all of this in any combination.  Wow.

I take it from what I have read here that if I wish to combine phases
together to get a multiple of 50A current, i.e. 100 or 150A (highly unlikely
methinks, 12kW should do for now %-0 ), I need power factor correction to
align the phases which are 120 degrees apart.  That would mean putting a PFC
on 2 of the 3 phases (between each phase hot and common neutral).  Is this
correct ?  What is the PFC cap value for this application, or is it more
complicated than this ?

Rgs
Ian





 > -----Original Message-----
 > From: Tesla list [mailto:tesla-at-pupman-dot-com]
 > Sent: Wednesday, 7 January 2004 6:57 am
 > To: tesla-at-pupman-dot-com
 > Subject: Re: Getting more input power
 >
 >
 > Original poster: dave pierson <davep-at-quik-dot-com>
 >
 >
 > >3 Phase:  each phase 120 degrees apart from each other.
 >
 >     Sometimes.
 >
 > >2 Phase:  each phase 180 degrees apart from each other.
 >
 >     If you are/were Nikola Tesla inventing 2 phase
 >     it was two phases at 90 degrees.
 >     (he later switched to 3 phase/120 degree...)
 >
 >     Granted, this is obsolete, however this is the
 >     _tesla_ list.
 >     8)>>
 >     best
 >      dwp
 >
 >
 >