Autotransformer to run Well Pump?

 Anyone using an autotransformer with a single inverter to run a 240 VAC well
pump?  I'm trying to put together a solar system on a limited budget and my
main goals are to run my well pump for about 15-20 minutes a day and my
refrigerator plus a few minor loads such as a few CF lights, alarm clocks,
AA battery charger, and DVD recorder/satellite receiver.  I figure I need
about 5 kWh/day minimum.  My well pump runs fine from a 4200/5000 peak
generator but the autotransformers I've seen (Xantrex and Outback) only go
up to 4000 VA.  Well, I've tried to understand the difference between VA and
watts but it's not sinking in.  My well pump is rated at 2 HP and about 11
amps while running.  I don't know the surge rating other than what my
generator is rated at.  Xantrex is selling their T-240 autotransformer for
the purpose of running "deep well pumps" so that leaves me wondering if it
will work or not.  One SW5548 should easily be able to start and run my well
pump but will the autotransformer be able to keep up?  I only need about 2
seconds or so of additional surge power and then it should be using about
2600 watts while running.

I'm planning on getting about 2000 watts of PV panels to start out and 24 X
220 Ah 6 volt batteries.  If one inverter will do the trick I'll have to go
with a 48 volt system but if I need to get two smaller inverters then 24
volts might be a consideration.

Lots of people here seem to prefer the Outback over the Xantrex/Trace
inverters etc. but the Outback system seems to be overly complicated and
needs a bunch of external units for control and programming such as the Hub
and Mate etc.  Xantrex appears, from what I've read, to have that included
in the inverters.  Is this correct?  I don't forsee ever needing more that
two 5500 watt inverters so the option of having four or more doesn't really
appeal to me.  I can always add the second inverter later but for now I
think I'd be better off spending the money on a couple more PV panels if one
inverter will work.

Thanks.

 

VA is Volt per Amp so using the 4000 VA rating, at 4000 volt you get 1 amp
and using ohms law to get its power capability you multiply the volts times
the amps which is 4000 watts that transformer can handle.
That ratio can vary in the real transformer as you will not be running at
4000 volts so using 240 volt, you divide 4000 by 240 = 16.6 so it can carry
16.6 amps at 240 volt out. The 240v times 16.6 amp = 3984 watts.
Hope it clears that for you. Jtt

 

Ignorance is curable :-)

Nick

 

 VA generally stands for Volt-Amperes.  The product of the rms voltage times the
rms amperage.



On 22 Mar 2007 14:39:29 -0500, nicksanspam@ece.villanova.edu wrote:


Bill Kaszeta
Photovoltaic Resources Int'l
Tempe  Arizona  USA
bill@pvri-removethis.biz