1000-Watt Inverter

You will probably get better answers as time goes on. But here is a start. To change from 1000 to 3000 watts, will require every one of the components to be able to handle three times the current. Starting with the wires going to the battery. Then the connections to the inverter. All the way through the circuitry. Every resistor, every capacitor, every transistor. they all need to be able to handle three times the current. I hope this helps.

Hello "Guest" (RAYMOND FROM NIGERIA)

Please don't use all CAPITALS in Forum Posts, it is regarded as shouting at the reader, and thus is bad manners.

You have made a 1KW Inverter, which works perfectly.

You cannot upgrade that Inverter for a larger Power Output.

The Inverter transformer, transistors, diodes and wiring would not permit increased Power output.

Retain your 1kW Inverter, which works well.

You need a full design for any increased power output, which will require many more parts, each of which will be more expensive.

Reply here, with

Kind Regards....

I'm not a hands on electrician, others may correct me. But I would have thought if the output voltage is unaltered then, you could connect three batteries and three inverters in parallel to give you the increased wattage. Need others to confirm this is correct.

Regards JD.

Hello jdretired

Because there are always variations in semiconductors, components and circuitry, running Inverters in parallel is generally not advisable.

What happens is that one Inverter delivers more output to the common load than the others, the semiconductors in that Inverter heat up, and thermal runaway of semiconductors in that overloaded Inverter often develops, while the lesser-loaded Inverters take a "holiday".

Kind Regards....

Sparkstation.

Thank you for that enlightenment, I suspected it might be the case. Was not sure whether they would hunt, and fault ratings would not cover the situation.

Regards JD.

Not to mention the problem of synchroising the output waveforms ....

There has to be a way to do this- after all if power stations can hook in together as needed to cover demand- or member failure- sometimes with load sharing- why can't inverters- I am talking here identical factory made units- if the demand is constant, the supply surely could cope- obviously close regulation is needed at all levels- or would an answer be switching at hi speed between parallel units, so the load sees an averaging supply?. Cheers, Neil.

Hello Neil Kwyrer

The complexity of trying to ensure both equal load to each parallel inverter, and the required phase synchronisation of the output voltage is far greater than the cost of a single large inverter, specially designed for the larger output.

In power stations or where AC alternators need to be run to supply a common load, initial synchronisation is not easy, but once synchronisation is achieved, the problem of ensuring that all connected alternators share the load properly still needs to be carefully managed.

Power Stations or parallel gensets AC, always use a single unit, generally the largest output alternator, as the Master, to which the other alternators are synchronised.

Refer: http://en.wikipedia.org/wiki/Alternator_synchronization

Download the Wiki .SWF animation here:http://msdaif.googlepages.com/Synchronization.swf

Complexity arrives if there are several Power Stations, far apart, with maintaining proper synchronisation, and in many cases this problem is overcome by the use of High Voltage DC (Direct Current) transmission links.

Trust that explains it for you.

Kind Regards....

G'day Spark emitter- thank you for your state of the art answer- the facts are: every inverter uses devices in parallel- usually mos-n-fets- in the primary to chop the dc- to the output- again power mos-n-fets of higher voltage in parallel- the number of mfs used & heatsinks etc are configured to the power- Now if instead of using xx to produce say 900W, using 3 x 300W, there has to be a simple way of hooking these units together to produce 900W, at a cheaper price. The simple fact is that a 300W inverter(modified sine wave) can be bought for $50- whereas a 900W msw costs say $500. Now there has to be a cheap easy way to interface these 3x 300W inverters so the output is in sync to produce 900W. Dang it!- I will probably have to do these experiments myself!. Regards,Neil.

Hello Neil Kwyrer

Please refer to my earlier Post on the subject: http://cr4.globalspec.com/comment/282114/Re-1000-Watt-Inverter

You seem also to forget that larger transformer + heatsinking + other factors for the greater capacity are also required.

These factors are exactly why larger Inverter units are more expensive.

I stand by what I wrote in the above Post, having done the cost/benefit analysis, and a good understanding of inverter technology to go with it.

Kind Regards.....

Hi Neil.

Sorry I missed your previous reply to one of my posts, I think our guest from Nigeria is probably a battler, and cost may be important, I respect the opinion of people such as Sparkstation and Del who seem to have the necessary practical experience, BUT, necessity being the mother of invention, I would like to think that people like yourself and other of the same ilk, might come up with an idea that might make it possible for people with limited resources to make social advancements with personal effect, such as our guest.

Regards JD.

Hello Neil,

This is not possible for this guy situation. They, I'm almost shure have a shortage of grid power and probably no much financial disponibility available to do what is needed to be done.

What topology do you use? Do you use voltage or current control?

B

I'm still working on bladder control.

HI Bob,

Work on that, my is half case capacity

Hello Raymond,

The upgrade you can make in the 1.0 KW inverter is very little compare to what you want, you can make adjustments to probable increase the power to 1.2 or may be 1.5 KW, to go as high as 3.0 KW that will the same as going to 4.0 KW a new equipment have to be made.

Running Three ,four or six 1.0 KW in parallel it is not recommended. Also take in consideration the more capacity the inverter is the more batteries Will be needed.

What it is going to be used for?

Just a word on synchronisation, on large units such as in a power stations or on a ship, severe damage can occur to the coupling between the prime mover and driven if the circuit breaker is closed out of synchronous. But my reference, ( Electrical Principals for the Electrical Trades by J.R. Jenneson), states that small unit can be closed out of synchronous, and they will pull into synchronous without damage. This refers to small rotary units, but others may advise this is not the case with solid state ( momentary loading). I also remember an auctioning system with regard to selecting output from different DC banks, can separate inverters be regulated? I agree that a larger unit would be the way to go, but for the benefit of the person asking the question and others, I labour the subject.

Regards JD

Had not consider phase angle, thank you, good answer.

Regards JD.

I have seen trucks without generators that relied on motor driven inverters. They used three separate inverters. But all were attached to separate power users.

Hello Sparkperson- the simple answer I just thought of is to thermally link the heatsinks of each unit- thus each system would perform over temp shutdown in case of thermal runaway- I have not explored this further, as my hands are full at the moment with a RPTV- the ONLY way to fix this #@*&() is to get a working set & swap parts- 10 years old so no maker support! Cheers, Neil.

Hello Neil Kwyrer

Please take the problem back to basics. (It is always best to reason from basic principles first).

There are 6 x 1000 Watt Inverters in parallel, supplying AC into a common load.

So...somehow you have managed to ensure proper AC synchronisation.

But there is still the problem you address above: How to insure against overloading and allow proper power-sharing among the connected Inverters.

So, the system is overloaded slightly, one Inverter goes off-line, using the heatsink sensor system you mention.

This leaves the 5 X 1000 watt inverters supplying a 6,000 Watt load.

The next inverter heatsink sensors trip that inverter unit much faster.....

And likewise thermal sensors trip out the next inverter....faster still....

And likewise thermal sensors trip out the next inverter....ever faster....

And likewise thermal sensors trip out the next inverter....even more faster....

And likewise thermal sensors trip out the next inverter....exponentially faster....

and so the process has continued, faster and faster, until there is just the one inverter left...a 1,000 Watt Inverter, supplying a 6,000 Watt load.....

That one trips out = Goodnight, because we are now in the dark, the lights having gone out.

It is what is called Cascading faults, due to thermal overload.

End of story.

Trust you understand now.

Kind Regards....

With larger generators being linked accidentally out of phase, one or both could leave their mountings in a big, heavy and dangerous manner!!!

Is the inverter a utility interactive type, like the ones used in PV system? If so, it will sync with the utility hz when paralleled or connected to the utility grid. Build three units of 1000 watts capacity and tie it to the utility grid. You'll get your 3 kw that you need. can someone correct me if I'm missing something here. thanks

Hello Bill H.

<"....I disagree with other posters which say this is too complex.

You are entitled to disagree with other Posters, including myself.

You could:

1. Replace the Output stage (and most likely the drivers for it) with components large enough for the power you want; or:

2. Duplicate the Output stage (and driver) and add current limiting resistors so you don't overload the circuit(s).

Somewhere you seem to have forgotten about a very large and extremely expensive transformer.

If you have built this much, you can increase the output without a lot of difficultly. It just takes picking off the signal before the amplification stage and making sure you have enough drive power to drive the larger output stages and limit the current in each output device.

Older ARRL Handbooks (for ham radio) have circuits which will help you understand the concept you have in mind.

I would, however, build a second unit with the modified circuits.

And how are you going to synchronise these units, and ensure proper load-sharing?

I admire your success in having actually built the project and encourage you to keep on experimenting, it is the best way to learn!

I also admire his success, and encourage him to keep on experimenting, it is the best way to learn.

There is no point in making something which cannot actually work, without greatly increased costs, costs which the experimenter cannot actually afford.

At different times in my life, I was sure I did know best, but asked for advice, received good advice and disregarded it, to my own personal cost.

Good luck!....">

I say the above comments, not to "show you up", but in the best interests of the Topic Poster, plus other readers of

It is best that "blind alleys" not be followed, irreplaceable lifespan portions not wasted, materials and other costs not wasted, don't you think so?

Kind Regards....

Who is this Spark espouser?- seems to know everything- perhaps said person could answer most important question of all- is this physical life all there is or is there an afterlife as in religion?. Or does said person not know or care either way?- KIND REGARDS Neil.

I understand from your part of the world you are blessed with voodoo

have you tried this yet?

funny ah..

They got oil but not electrical energy, I don't understand. Cannot lite the voodoo no even with the 6000 watt inverter he wants to build.

I think I know what you are looking for but I can only give the the how to, approach and not the exact part by part, as long as you know your load will never exceed the total output of the inverters the sinking of the wave forms is all that is needed! You said you built this unit and I am guessing that the others will be to (although if you can find the sections in the circuit in the ones you buy so you can modify them to match it should work with them as well). Down to the details, in order for an inverter to generate the wave form it has to have an oscillator circuit to create the 50 or 60 hertz output this may or may not have a timing trigger to maintain the frequency but you will need to stop the the oscillation and set up an external trigger circuit to inject the timing signal to begin each oscillation so all the inverters will have the same clock speed and sync! Also make sure each inverters clock pulse is injected on the same starting point in the oscillation cycle IE: starting at 0 reference and starting the positive cycle of the wave form, if all the inverters have to wait for the external sync pulse they should produce the same or close enough wave form to live together. Different inverters may not have the very same waveform so they may have some Resistance to doing this but if you build each one your self with the same identical parts and specs and incorporate the same mods there really should be no reason this wont work, also make sure your wires used to connect the sync signal are all the same type, gauge, length. You might also link the shut down triggers between the units together so if anyone of them trips a safety shutdown the all will at the same time, you could again isolate the trigger points and make 1 external shutdown controller so that if there is a problem with any one it will release a relay on you battery source immediately braking the connection to the inverters protecting everything.

Hope this might be of help, Have a great Day!

Welcome. Nice answer. Informative, and concise.

Thank you!

For years I taught my self electronics to repair old tvs, vcrs, and microwaves and in tvs the oscillators were the thing to understand if you were trying to service the horizontal or vertical circuit problems!