Inverter i/p's vs o/p's

[Grant MacLeod]

Hi all

I'm just rigging up to build a Hugh P. axial flux windmill and I need to make the voltage output decision.  i.e. What DC volts do I want out of this?

Thinking out loud here:

Windmill produces AC

It is rectified to DC to store in batteries

Batteries fed to inverter to convert to AC.

Very commonly we see in North America 12 VDC to 120 VAC inverters?

.... sorry if these questions are answered in the archives but I haven't seen them.

What DC voltage do I need to feed to a 220 VAC output inverter to get the 220 I need for my well pump?  24 VDC maybe?

Is this the reason the windmill plans often specify 24 VDC output options?

Is it possible to buy a 12 VDC to 220 VAC inverter?

I'm going to be in Scotland in a couple of weeks?  Would there be a price/availability advantage to me buying an inverter there since 220 VAC is line voltage and more commonly used?

Thanks

Grant MacLeod

[AbyssUnderground]

Is it possible to buy a 12 VDC to 220 VAC inverter?

Yes it is. I have a 600watts (1500watts surge) 12VDC to 220VAC inverter. It cost me £20 ($40) but it was on offer. It will cost around £50 ($100) at normal price.

[dinges]

Your answer could be answered by searching this board: searching for 'inverter' you'd find a lot about them. 'voltage' or 'what voltage to choose' will tell you more than you ever wanted to know about the pro's and cons of various voltage systems:

Hmm, just searched myself and none of the threads I had in mind came up (the ones that discuss 12, 24 and 48V systems)...

As far as the well pump goes, have you thought about replacing it with a 120VAC pump? That may be an option too, perhaps easier and cheaper (in the long run) than a 220VAC inverter.

Because, if that inverter goes defect, will you return to Scotland for a new one? Or can get it locally repaired?

If your plain vanilla 12V-120V inverter goes defect, you'll have much more options for replacement or repair.

Or, even more efficient and simple, replace that well pump with a 12 or 24VDC one? You'd need much bigger cables ofcourse (how long is the run?), but your setup would be simpler and more reliable, I think.

Just some of my thoughts on the issue.

Peter.

[Grant MacLeod]

Yes, my first search through the archives found lots of discussion on inverters but not these particular questions.

Interesting points.  I'm not sure that a 120 VAC or espacially a DC Voltage deep well pump is readily avaliable in our area.  I should investigate though and of course there is always mail order.  

This would be a backup system if the mains go off-line like what happened to us a couple of years ago.  After hurricane Juan hit here in Nova Scotia we lost power for 6 days.  If I was to boot up the backup and the inverter suddenly decided to die after a couple of days then I guess we'd be back to walking down to the local lake for water again   In those kind of dire straights it's unlikely that any replacements or repair facilities would be immediately available anyway.  For the common 12VDC to 120 VAC or the more exotic 12 VDC to 220 VAC.

Thanks

Grant

[Grant MacLeod]

Is there any disadvantage to using a 12VDC to 220VAC inverter (compared to 24VDC to 220VAC) other then the higher current at the input and so bigger wires into the inverter?

Thanks

Grant

[jimjjnn]

You need 50 Hz or 60?

[dinges]

That could be an issue too, but not in this case, I think, where the purpose is to drive a motor.

However. Another thing to consider. I have heard that 'some' inverters have problems driving capacitive or inductive loads, like motors. Meaning that, to drive a 100W motor, one would need a 400W inverter. A 100W inverter might not be able to properly operate that 100W motor. And there's the initial current surge too, that the inverter should be able to handle.

To the original poster: what is the current rating (voltage, ampere, power (W and/or VA), cos phi, etc. of your well pump?

And, do you intend to drive other loads with the inverter too?

Finally, a simple (but not so good solution, I think) would be to add a transformer to step up from 120V to 220/240VAC. Any transformer could be used as an autotransformer for this purpose. But, transformers behave like inductive loads, which inverters don't like too much. And there's an extra conversion loss: I usually assume transformers are only 80% efficient. Add another 80%-90% for the inverter. But you would be able to use standard inverters (12VDC->120VAC). The efficiency of switching to a 12VDC motor is 100%, but then you've got cable losses to take into account. Plus, efficiency isn't your biggest worry, if you'll only use it in emergency situations (which usually last not that long). Reliability would be much higher on my list, in those cases.

Decisions decisions....

Peter.

[kenputer]

Grant,I'm also in Nova Scotia and have put in quite a few submersible pumps and yes you can get 115 volt pumps,how deep is your well? knowing that I can make a better recomendation.

Ken

[Grant MacLeod]

Hi Ken

My well is just 60 feet.  I'm surrounded by 300-400 foot poorly producing wells in the neighborhood so I consider myself lucky  

Grant

[Grant MacLeod]

60 Hz Jim

Grant

[Grant MacLeod]

Let's see.  The only pump spec I have is that it is 1/2 hp 220 volts.  ~378 Watts.  The pump is in the well itself.  I do envision a multi-use back-up system.  Right now I have a drainage problem in the basement and if the rains are heavy and the power goes out, my sump pump stops and I get flooding.  I've seen 12 VDC sump pump systems so that is less of an issue.

Grant

[K3CZ]

Grant:

Your questions are valid and appropriate, but there are an number of alternatives available, all of which will work effectively.  Keep in mind that any 220 volt inverter you buy in Europe will have 50 hz output, while such models available from US mfrs. are designated for "export", 60 hz output assumed for all models destined for the US mkt.

To keep the whole system at 120volt output and use a 120/220 transformer for the sole 220volt load is an allowed use on the Xantrex SW models at least, according to the manual. In general, sytems up to 2500w. can be comfortable with a 12volt battery bank, but 3000-4000 will work better on 24volts, and by the time you get to 5500watts, you will need a 48volt bank to hold all electrical parameters within acceptable limits.

An addtional option is a seriesd-output inverter pair (of any input voltage) that will get you a US-normal 120-0-120 vac distribution from two identical inverters. This is an option offerred by most inverter manufacturers.

No need to arbitrarily changeout your water pump - a 1/2hp 220volt unit will work on a 4kw inverter, and mostlikely as well on a 2.5 kw unit.

Some more detailed system layout plans from you would allow a more accurate reccomendation.(Where are you in the world?)

                                      Good luck,   VAN    K3CZ & PE

[Ungrounded Lightning Rod]

Does your pump have a "soft-start" or a variable-flow controller (such as the "Balanced Flow" from Goulds Pumps) or is it just an AC motor feeding a pressure tank or a raised tank and driven directly by an on-off pressure or water level switch?

If you have one of the fancy controllers you have a phase/frequency converter that may be much more (or maybe even much less) picky about the power supply, and you should consult the manufacturer for their recommendations for running it off-grid.

[Grant MacLeod]

East coast Canada Van

Thanks

Grant

[Grant MacLeod]

I'd have to say the second option.  Pump fills a pressure tank.  A pressure switch turns the controller at least on and off.  I don't believe there is anything fancy in the controller.

Thanks

Grant

[SparWeb]

Grant,

I have a similar situation to yours, and have found myself thinking along those lines, myself.  When the power goes out for over a day (happens once every 2 years or so), it's to get water that I'm forced to leave the house.  So far this hasn't happened in winter, but it's only a matter of time...  (I live 1/2 hour away from Calgary, by the way.  My grandparents, in Halifax, lost several trees to Juan, themselves.)

I like building windmills, but I don't see that as a reliable way to backup my power.  Now when I'm just starting out, that is.

The simplest solution I can think of is an "uninterruptible power supply".  It charges a battery and keeps it topped up.  When the power goes out, it goes into inverter mode and powers AC devices off of the battery until main power is restored.  Simple consumer devices are designed to keep your computer going - you plug directly into them.  Other types can be wired into your well pump's wires.  This could be expensive, as I'm talking about an "industrial" type of power supply that businesses use to keep computers, refrigerators, security systems, etc. running.

The next simplest solution, and just as expensive, is a portable generator.  My in-laws, who live near Montreal, installed one after the Ice Storm.  They wired it into the house, on lines rated for 40 Amps or so, to a separate bank of outlets.  When the power went off, they shut off the house's main breaker, fired up the gen, and plugged the fridge and some lights into the bank of outlets.  If they'd been more ambitious, they could have patched this into the house's main circuitry, but that would require some serious interlocks on the ON switches to prevent things from blowing each other up.

Since you want "just one", you might look around town for businesses, fire stations, hospitals, etc. that are changing out their back-up power equipment.

[Grant MacLeod]

Good points Steven

I'd say there are now 50 times as many generators in the area as compared to before the big hurricane.  It is definatly the convenient power out solution.  But a windmill will be the fun solution!  

My friend brought a couple of batteries by yesterday.  He works at a boatyard and can scrounge pretty decent batteries the boat owners routinely discard.  We'll be scrounging at the junkyard for hubs soon.  Pulling apart old motors for magnet wire as well.

Seems like magnets are the only part that a couple of junkyard scroungers can't find!

Grant