Inverters Switching or Transformer type?

adas

Aloha, Which is more effecient. Switching (solid state) or the heavy transformer type? Both modified sine. The obvious answer should be Solid state, but I understand that the better the wave form is the more effeciency, not so much the power-hog transformer. comments?? (the techie that is selling me the heavy transformer type, says he had it on the scope and the wave is very very close to a sine wave.

Frank

mike95490

Re: Inverters Switching or Transformer type?

if it has an output transformer, it WILL be close to a clean sine wave. A mod-sine does not play well with transformers.

BB.

Re: Inverters Switching or Transformer type?

Go by what the technical description of the inverter is... Typcially, a sine wave inverter is heavier because of the extra transformer+windings required for it to be a true sine.

A modified square/sine wave inverter can use a smaller transformer--so is cheaper and lighter.

The problem with the square wave is a transformer (or motor) can overheat because of all the higher frequency components above the 50/60 Hz fundamental... That extra energy can be as high as 20-25% in those upper harmonics (if I recall correctly).

But when you are working with older and non-consumer equipment--it is sometimes difficult to know what that extra heavy transformer is for... It, for example, could be part of a ferro-resonant circuit intended to clean up line noise. Or have multiple taps to adjust input to output line voltage on a UPS--without the need to turn on the inverter section of the device.

-Bill

adas

Re: Inverters Switching or Transformer type?

mike90045 wrote: »

if it has an output transformer, it WILL be close to a clean sine wave. A mod-sine does not play well with transformers.

So I understand what you are saying... Since it has the heavy transformer...this is the output transformer?

And the solid state one has transistors for regulating output?

a mod-sine does not play well with transformers.......what do you mean?

So the transformer type inverter will be a closer to sine wave?

How about effeciency?

thanks
Frank

BB.

Re: Inverters Switching or Transformer type?

All inverters have some sort of "switches" (transistors, FETs, etc.)... On or off. How they are wired and what they are connected to (type of transformer) all goes into whether or not they are Modified square/sine wave or true sine wave...

Just looking at the outside of the box and its weight will not always tell you enough to determine what it is you are dealing with.

If you have a manufacturer's name and model number--might find out more about it on the web.

As to whether or not you can use a mod sine or need a true sine, it depends (a lot) on your loads and your needs... A true sine wave inverter will drive inductive loads more efficiently--a modified square wave will put a lot of energy into the windings/cores of inductive loads because of the square wave (upwards of 25% of the output of the square wave inverter will be lost as heat)...

In general, it is not possible to efficiently or effectively "filter" a modified square wave output inverter into a clean sine wave output using transformers/inductors/capacitors (that I am aware of--I am certainly not an expert here).

Perhaps, if the vendor is willing to work with you--try one or both units at your site and see how everything runs and how much power you use--that may give you an answer right there.

-Bill

adas

Re: Inverters Switching or Transformer type?

Aloha, here is the site of the inverter I am interested in.
frank

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110268499244

BB.

Re: Inverters Switching or Transformer type?

Frank,

Cannot tell much from the manual--probably an OK piece of equipment within its limitations...

Just general observations--many (most? all?) modified square/sine wave inverters have to have floating AC outputs if the DC input is ground referenced.

So, if you need ground reference neutral (usually required by NEC)--you may have an issue with these guys (I don't know for sure--either way).

This may become an issue if you need to use GFI protected outlets... A GFI outlet should work, and should test normally--but I am not sure. Normally a GFI is tested by placing a small load on the "hot" side of the outlet--depending on the exact ground reference (if there is one), the self test may not work reliably...

And, as you know, 3.6 kWatts of power is a lot--if you don't need this much power, the idling/low power efficiency may not be very good with such a large unit. And if you need this much power--you got enough solar backing you up?

I guess--if the price is really good and you need the Mod Sine power--I don't see anything that screams no--But I would also look at the other inverters out there too--ones you can repair/replace if something goes bad. This one, you may be out of luck if it fails.

-Bill

I guess I should also add that the DC Vmax input voltage of 29 VDC is a bit low--Should be over 31+ VDC to allow fast charging and equalization (perhaps, this is not a real issue--just don't know)... Sort of seems like this is designed for going in a vehicle.

Solar Guppy

Re: Inverters Switching or Transformer type?

Just buy either an Outback FX or Xantrex XW inverter. I have seen 3kw FX inverters for under 1500.00. Pure sinewave and you get a warranty

The eBay thing can be DOA, or work once then die, then your out 500+ shipping on a big piece of junk

Your system is so big, it makes no sense to not have real sine wave inverters

adas

Re: Inverters Switching or Transformer type?

Aloha, I am getting spanked by trying to go to cheap on the inverters and save money. I am adding some more panels and going up to 6840W from 4560W, adding another FM80 for a total of three. I am going to trying out the 3.6K inverter I talked about and if it does not work for me, sell it here in Hawaii. But probably bite the bullet and get a 3.5k? outback sine wave.
FWIW I tried the Aimes "generic one brand many labels 5k 24v inverter" that costs $500.00 from here and they are only so-so.

http://theinverterstore.com/the-inverter-store-product.php?model=pwrinv5k-front-rgb

Frank

BB.

Re: Inverters Switching or Transformer type?

Frank,

Out of curiosity, what did you find that was "so-so" about the generic inverter?

-Bill

Solar Guppy

Re: Inverters Switching or Transformer type?

Just alittle hard to understand your thinking, you bought 6kw of PV ( 25k+ ) and you trying to save 750 on the inverter? , thats what I'm trying to point out. Get a real inverter as your WAY beyond some cheap cabin system and the use of junk mod-sine inverter. Anything of the power class will smoke and die using mod-sine ( your loads ) .. you need real sine, and based on the system more like a XW-6048 from a load stand point

nigtomdaw

Re: Inverters Switching or Transformer type?

Have to agree with SG on this one pennywise (centwise) pound foolish (dollar foolish) comes to mind

Looks like you spend a fortune on a blue printed engine and want to drop it in a Pram

I guess that sounded a bit waspy

adas

Re: Inverters Switching or Transformer type?

nigtomdaw wrote: »

Have to agree with SG on this one pennywise (centwise) pound foolish (dollar foolish) comes to mind

Looks like you spend a fortune on a blue printed engine and want to drop it in a Pram

I guess that sounded a bit waspy

Aloha, nahhh, I'm thick skinned. The only thing I can say that although I am beyond running a cabin, I also am not trying to run a household with sophisticated electronics. I am just trying to run a machine fabricating shop with grinders, fans, saws, mig welder, etc. I was not about to risk a $2500.00 Outback and have it pop with the welder turning on with the other tools. I would rather pop a cheap unit. I will be buying the Outback 2436 or (3624) for the office.

The Aimes unit tends to overheat, even though it may be 90 degrees in the room, I have to keep an fan outside blowing on the unit, even though to the touch the inverter is cool.
The Aimes unit does not run a microwave very well. Otherwise it is OK for $500.00 @5000W.


My first inverter was a prosine 1750 @ 12v but I moved to 24v and now will sell it for $550.00 or so

My second inverter was a tripplite 2400 off ebay for $400.00 (heavy transformer) and this ran appliances nicer, but was old and died on me.

I will keep the Aimes unit as a backup for the shop and buy something better for the office system.

frank

niel

Re: Inverters Switching or Transformer type?

if you are concerned of the welder doing harm then just run the welder on the aimes and run motors and such with something better like the prosine.

BB.

Re: Inverters Switching or Transformer type?

Thinking outside the box here---What about DC welding just using your battery bank?

Here is a 24 VDC nominal 200 amp MIG welder intended to connect to storage batteries.

From the company's website--I do not see any current regulation--so I am not sure you can connect it you your "forklift" batteries or not (safely). Intended for 5 minutes on, 5 minutes rest duty cycle.

Here is another company that is "The Industry Leader in D.C. Welding Technology". Website is terrible--you probably would have to call them to see if anything of theirs would work for you.

And yet another battery powered DC MIG welder.

If you had a good way of getting a couple Horse Power from your batteries into a spinning motor--using an alternator can make an OK welder too. This is a commercial version (I think).

Hobart may be coming out with a "battery powered" welder soon.

Hmmmm... Don't know that any of these are practical for your needs.

I know in the "old days"--the really old timers would just pull out a car battery or two and hook up their stick holders to them and start welding.

-Bill

Telco

Re: Inverters Switching or Transformer type?

That setting up a motor to spin a generator for the welder sounds like a pretty good solution to me. While it would be less efficient, it would also isolate the welder COMPLETELY from the electrical system. Would suck for some freak backfeed to pump back through the whole system. I imagine the savings in not having to buy and install multiple inverters as you are planning to do would more than cover a few extra panels to cover the power used by the motor since that motor would not put the load on that is currently blowing inverters for you. Be worth some thought.

solarix

Re: Inverters Switching or Transformer type?

I don't have that much experiance with the new inverters, but I have a long history of repairing power supplies - both transformer and switchers. The big difference is that the switchers are much more complex, therefore more difficult to repair and they are much lighter with little "inertia" therefore any transient spikes and surges just rip through them and will blow up the control electronics much easier. For reliability and maintainability, give me the heaviest one every time. Ya, the manufacturers like the switchers because they are easier to build and installers like lifting them on the walls, but as a user, I'll pay for the heavy copper.

Efficiency wise, there isn't much difference and either one can produce a fine sinewave. The low frequency switching of the transformer types lose most of their losses in the "on" resistance of the transistors whereas the high frequency switchers lose it in the switching time losses.