Auto Transformer question?

Re: Auto Transformer question?

verdigo wrote: »

Looking at split leg balancing are all these units the same as long as they are 240v to 120v at 60hz? Lots of these units on ebay but the descriptions don't specifically state they can be used for leg balancing. This is such a unit http://www.ebay.com/itm/Auto-transformer-4kVa-120-vac-lv-240-vac-hv-express-/390603719078?pt=BI_Circuit_Breakers_Transformers&hash=item5af1cbc1a6

Thanks

Dennis

Would be good for a 50Hz system, might run OK for 60Hz

Re: Auto Transformer question?

If it's a 50 Hz transformer it should work fine on 60 Hz.
However a 60 Hz transformer would probably not work well on 50Hz, it would tend to draw excess power and overheat due to insufficient impedance for 50 Hz operation at it's rated voltage.

Re: Auto Transformer question?

I looked at that one, but decided to go ahead and spend the extra money for the PSX-240 when they had the earth day sale and it works great for running the 220 VAC heat pump. Thanks NAWS!!!

Re: Auto Transformer question?

WisJim wrote: »

If I am in need of an auto transformer to get 240 volt output from my 120 volt Inverter, and don't want to spend $300 to $500 on an Outback or Xantrex/Trace unit, what criteria should I be looking at? For example, what should I search for on eBay or what specifications are critical if I look on surplus electronics sites? Thanks!!

Jim in Western Wisconsin

What load is planned for it WisJom? And what do you have for an inverter?
That info will help.

Re: Auto Transformer question?

waynefromnscanada wrote: »

What load is planned for it WisJom? And what do you have for an inverter?
That info will help.

Don't forget that the windings of the autotransformer only need to be sized to handle the power of the 240 volt load itself. Any additional 120V load you add connected directly to the inverter output does not put any load at all on the autotransformer. And the thermal mass of the transformer is large enough that, except for voltage drop considerations, you do not really have to worry about sizing it for surge current, even on the 240V load.

If you are also using it for leg balancing of a 240V generator, or to provide for 120 volt loads on the synthetic phase, then you have a more complicated calculation to do.

Re: Auto Transformer question?

cheaper, No Kidding! $200 just or the box and some wire etc...

Re: Auto Transformer question?

You can also look for isolation transformer. The most flexible is one that has two primary and two secondary windings so you have the options of 120v to 240v either way with or without isolation or autotransformer connection.

One important difference between an autotransformer and isolation transformer is an isolation transformer wired as a autotransformer can deliver twice the VA rating. I have some 2 KVA rated Thordarson 23V615. Wired as autotransformer they can run 4 KVA.

OutBack FWX-240, 3 kVA 120/240 Auto Transformer weighs about 25 lbs.
Xantrex T240 Autotransformer 4kVA Auto transformer weighs 39 lbs - 7 to 9 lbs of the metal cabinet.
Thordarson 23V615 2kVA isolation transformer weighs 52.5 lbs.

Generally, more 'iron' (weight) is better. It depends on losses across load range. Again generally, lower lbs./VA means more losses at either lower load or higher load end of VA range. (Outback sells an X-fan option kit) A low weight per kVA is usually wound with fewer turns per volt (to prevent core saturation) resulting in poorer power factor and more losses at low end loads. Leakage inductance is also a factor, generally worse on low weight per kVA. Allowing higher leakage inductance allows higher KVA loading without saturating an undersized core, with down side of more losses and more voltage fluxuations versus load level.

Another thing, being it either isolation or autotransformer, they almost always wind their secondaries with about 1.02 to 1.05 times their primary winding turns per volt ratio. This is to make up some of the losses through the transformer, preventing lower then target voltage on secondary. This has ramifications if you are using them to balance 120 v loads with an autotransformer.

Re: Auto Transformer question?

KozmoK wrote: »

I am going to take two 327w panels in series to a midnight classic 150 to a bank of 12v 540 ahrs to a xantrex pure sine 1800 to a step up transformer. Nothing else will be on this circuit.

I guess I am going to go for the Outback PSX-240 Auto transformer 120/240VAC big price tag

Rethink. How about putting those batteries in a 24 volt configuration? You can use thinner cables and have fewer parallel batteries (more stable).

Your classic will be more efficient down converting the Vmp to 24 volts than to 12 volts, and if you haven't bought it yet, you could get by with a smaller (cheaper) controller such as the Midnite Kid.

Look at the Victron Phoenix inverters... some of them make 230 volt AC at 60 hz. They are efficient and have very low tare losses. You would not need the autotransformer which also consumes a few watts.

--vtMaps

Re: Auto Transformer question?

The Victron Inverters are interesting - looking at the data sheet here: http://www.victronenergy.com/upload/documents/Datasheet-Phoenix-Inverter-180VA-1200VA-EN.pdf

I see there is only one model with a dip switch to set the hz. And that model is lower in w's 48/350

The reason I am going down this road with my idea is I already have all the equipment I listed. I'm not against getting another inverter if its in the $600-800 range.

The pool pump I have is controlled by a Jandy Aqualink pool system - (iphone app controlled, etc) so its already paired with the motor. It has a control box with big relays feeding to components of it, so I could easily feed in my own 230v source to the relay.

vtmaps wrote: »

Rethink. How about putting those batteries in a 24 volt configuration? You can use thinner cables and have fewer parallel batteries (more stable).

Your classic will be more efficient down converting the Vmp to 24 volts than to 12 volts, and if you haven't bought it yet, you could get by with a smaller (cheaper) controller such as the Midnite Kid.

Look at the Victron Phoenix inverters... some of them make 230 volt AC at 60 hz. They are efficient and have very low tare losses. You would not need the autotransformer which also consumes a few watts.

--vtMaps