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transformerless inverter

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May 3, 2009
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Anyone can help me about transformer-less inverter???? i.e. electronic inverter

i am basically talking about electronic inverter not the inverter that is so used (power inverter).

Anyone have some sorts of material to share.. please send me i am in need very quickly.........

you can go to Refer to there seminars, mainly papers authored by lyod dixon. apart from that power electronics books by pressman and onother by Ned, Mohan. The term Transformerless dose implt hat there is no bulky 50 or 60 hz transformer in the inverter circuit, however there may be a feww high freq transformers and choke of much smaller dimensions in the circuit
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thank you tillu.

I am talking about it's efficiency & specification, wattage, los, why it's better than power inverter (inverter with transformer), are they really good... these type of specifications & who are manufacturing the transformerless inverter.

I heard that there is much less loss in transformer less inverter than power inverter. Any idea why???

And some other facts...

Can anyone help me about these??? any expert or expericed persons or anyone who knows something about it.

please i need help....

lots of interters are transformerless, it is no problem to design.
see here:

in addition to isolation advantage (i.e. this specification may be required by your customer...).

the transformer has losses, don't forget that. it also needs specific type of protection against saturation and other faults which costs you extra in design effort.

the transformer allows your PRIMARY side to be low voltage. this allows you to use low voltage rated mosfets (which is SOMETIMES more efficient than high voltage equivalents). MOSFETs can switching high frequency too, so the transformer is small. IXSY offers 75V 1500A mosfet module with 5mohm RDs_on (from memory). so this is very efficient and useful for higher power applications.


you cant make an inverter without transformer but can reduce the size of transformer by increasing the operating frequency. for high frequency you need a material who's (molecular) dipoles can respond to ur system frequency. if you double the frequency the size will be almost half.

You CAN design a transformerless inverter. Of course, you must use PWM control. The snag is, that the DC Voltage must be at least the peak voltage of the output voltage. So, for an output of 230V AC you need the peak, which is 325V. To that you have to add the on-state voltage of the Transistors (nothing else but IGBT's makes sense here). If you use a bridge circuit, you have 2 voltage drops that you must add, typically about 2 x 3V. That makes the minimum DC voltage 331V. Since you probably feed from a Battery (that is usually the reason for using an Inverter), you must still get 331V when the Battery is at it's lowest discharge voltage. For a lead-acid Battery that is normally about 1,7V per cell. So you need a nominal Battery voltage of 390V (or 33 x 12V Batteries in series) to give you 230V AC without a Transformer. But beware - there is no isolation between the battery and the AC output.

MR Cool stop spaming all forums especialy when you offer nothing much but a room filled with designs that do nothing and even have been shown on many sites that say they do nothing also most of them do not make sence.
this is the 3rd room i have seen him in doing that.

Added after 5 minutes:

i think he wants a DC to DC convertor.
12volt batt to some fets and coils and caps ect to make 110 or 240DC then to use more fets to switch the 240volt with a sinewave. but as mfarooq1 said you will need a high freq Transformer.
Yetisouth yes its best to have more voltage such as 300+ and then have a feed back circuit that goes to a comparator that will monitor the voltage state of the batt's so when voltage drops the invertor will still give the same voltage but also when you have a load on a invertor or any power you will get a voltage drop and because we are trying to make a source of voltage best to try to eliminate the load drop so when there is load its around 240 with max load.

Hey, thanks for your reply. I was ill for some days that's why I could not reply. I don't need how can they make. I need who are making these transformerless inverters. I need some name of manufacturers & their contacts.

I am mainly interested in inverters only, though including package (IPS) is my concern. My main concerns are transformerless inverters, because in our market in Bangladesh, in every applications, where inverters are used are all power inverters (i.e. with transformer), You know, in power inverter, the loss is much more than transformerless inverter because of only transformer, and transformerless inverter is more efficient, long lasting, much lighter & cheaper. These couple of things I heard only. I know you already know these things. I need some comparison statistics between power inverters (i.e. with transformer) & transformerless inverter, some technical data. I need these inquiries that I told so far. Because I need to study the market & also the feasibility here in Bangladesh.

blackice504, you don't know what you're talking about. let's see what you provided? oh.. i see. . nothing.

i uploaded quality designs that came with a lot of documentation and discussion on the link i provided above. how can you say they do nothing? show me the evidence. what parts of these projects do not make sense? i'll happily explain it to you. if you still feel the projects are no good, then explain yourself better than "some sites say they no good" but don't even link to the sites. if you can convince me that i'm wrong - that they are NOT projects worth sharing - then i'll stop refering to them.

but for now i think the links to the school projects are pretty good. they are nice designs. they are NOT PROFESSIONAL GRADE as they lack detailed analysis, practical implementation etc... that's true.. but on the net, you never find that sort of thing. at least what i posted were several examples of WORKING inverters and some that come with schematics. i have had a LOT of positive feedback from those links from people that have appreciated the upload.

from time to time this forumn gets some requests for inverters, how they work, and design examples. it is handy to have a thread where this info can be contained. that's why i refer to that thread.. to help with organization of the message board.


ok, Mr. Cool, I think you got angry with blackice504. That's nothing to do with me.

Now my question is. Is there any company who are manufacturing transformeless inverters for home appliances, not for solar or renewable energies. I found lots of manufacturers, but they are all for solar or renewable energies.

I want to use that type of inverter (transformerless) in IPS/UPS. Are this efficient enough?? Is it feasible??

ya.. you're right i was angry.. that's not usually like me.

the inverter itself is pretty benign. it has no idea what the source is, and what the load is.. its job is to turn DC into AC and that's it. so yes, the SAME topology works in many many applications.

the question of transformerless is odd. the transformer is really only there for any (or all) of the reasons below:
1) your design requires isolation from the AC load (could be safety, operational, system dependent whatever the reason)
2) your design has a large disparity between input DC voltage and output AC voltage so you use the step-up/down properties of the transformer

if your design has neither of the above requirements, then you don't need the transformer.

now.. if you start with the inverter building block and THEN decide to use it in UPS that is different .. slightly. because the UPS has an ADDED design requirement which is to be able to switch sources without interruption to the load. so you ADD this feature on top of the basic building blocks.

see what i mean?


Mr. Cool,

I guess you did a great job on this transmerless inverter, at least to me these are a good learning and reading about the HF conversion topologies.
Great contribution to the net or to this group. I am going to use your contribution as baseline information and expand to my real project soon.

big D

im making a 12V-240V,200W inverter. If i using a high frequency and the size of transformer will be smaller. But how can i tune back to 50HZ output?


how can i tune back to 50HZ output?
You'll most likely rectify the high frequency voltage to a secondary DC bus and operate a 50 Hz H-bridge converter,
with either square wave or sine modulated PWM output. If you read thoroughly, you'll see it mentioned in the previous posts.

But how can i tune back to 50HZ output?

this is the beauty of modulation theory. the switching frequency is high allowing the magnetics to be small(er) but the fundamental is a different frequency (low)


i need to produce an output of 500 watts at 230 volts....input = 12 V.

Which is better - using a transformer or boost circuit?? pls can you tell me the advantages or disadvantages of each.

hi guys i need a circuit diagram for 12vdc to 220Vac @ 50hz inverter with 300wattages with an automatic switch over if my 220Vac mains fails

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