Modified-Sinewave versus Sinewave Inverter

Hi All,


Lately there was a demand for inverters in my local market. So, I designed and produced updated versions and naturally I made them of the modified-sinewave type to lower their cost; 12V/220Vac/500W, 24V/220Vac/1000W and 24V/220Vac/2000W.

The majority of my buyers, who are house owners in my city, prefer installing a modified-sinewave inverter instead of a true sinewave one. And if they have already installed a good one of the latter, they remove it to install the former (modified-sinewave). So it is not a question of price or reliability.

Could anyone guess why? :-D

Wishing you all a Happy New Year... full of new learning's ;-)

Kerim

Dear Mr Karim
Happy New Year and good wishes to you. Before coming to your question, I would like to ask you one question:- Being a business man you suppose to have good depth of knowledge about three things 1. Market demand 2.Reason of it and 3.source of that. If I was in your position I would not depend upon some body’s guess. My guess
Is sine wave inverter that you can find in your market is not sustainable designed.

Best regards
M Rahman.

Hi Rahman,

Your remark is good and that is why I pointed out in my OP:

And if they have already installed a good one of the latter...

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I meant they had a reliable sustainable sinewave inverter likely a costly one... and perhaps theirs is better than mine in this respect ;-)

That is why the answer of my OP question is not easy to find out till it will be heard :smile:

In fact, I doubt that someone will find it though it is technical and practically very important.

Good luck.

Kerim

Hi All,

I think it may be rather impossible to get the right answer without giving you some hints first, since most probably it cannot be found by searching. ;-)

So here is hint_1:

Most houses are content to have low power inverters (500 to 2000W) for temporary mains cutoffs.
Their appliances usually require a higher power and are grouped on a few power lines (sometimes just one line) from the general board.
Only some of them could be supplied by the installed inverter and they might be anywhere in the house.

If this hint_1 will fail, I hope hint_2 will not ;-)

Kerim

Are u an engineer ?

pankajs said:

Are u an engineer ?

Click to expand...

Did I look otherwise? :???:

From post #1... So, I designed and produced updated versions...

Click to expand...

:smile:

Hi all again,

Naturally, when someone didn't face a kind of problem yet, he likely doesn't know about its solution too.
Also, technical requests needed by local consumers (local market) could differ greatly from one region to another in the world.

So here is the problem related to this thread:

Suppose you have a house (if not, you may skip reading this post ;-) ). And it happens that its AC mains voltage could be off anytime. You don't see necessary installing an emergency AC power unit to keep supplying the whole house. Perhaps a 500W inverter is enough since it can supply a TV set and some lights. So a question may show up in this situation:
What is the best solution in term of simplicity and reliability to isolate automatically the rest of electrical apparatus in the house which may be connected on the same power line (this is likely not the case in deluxe apartments :smile: ) when it (the copmmon power line) is flipped from the mains to the inverter AC output?

The answer of the question mentioned on post #1 is somehow very clear now. I hope :roll:

Kerim

I don't know the answer but it is a topic of interest. I looked into inverters to find out which to get for Y2K.

Sinewave is preferable but also most expensive for a given watt rating. Modified-sinewave is slightly more efficient and less cost.

However I purchased a sinewave inverter because I read that motorized appliances run 10 percent more efficiently on sinewave. This alone brings it about even with modified sinewave. Furthermore, motors start up easier on sinewave. All devices are quieter with sinewave, whereas the square waveforms cause some buzzing.

I ran our refrigerator during blackouts. (Powering it from a running car is just the ticket.) I have run it from all 3 types of waveforms that inverters put out. To supply startup surge, and keep it running, seems to require 1500 W capability from the inverter. (Maybe 1000 W.)

What is the best solution in term of simplicity and reliability to isolate automatically the rest of electrical apparatus in the house which may be connected on the same power line (this is likely not the case in deluxe apartments ) when it (the copmmon power line) is flipped from the mains to the inverter AC output?

Click to expand...

I would suppose a few extra contacts in the changeover switch. The changeover switch can be manual or automatic. But you are talking about *automatic* isolation of one half of circuit branches inside the house from the other half.

If there is a deciding factor that makes sinewave inferior to modified-sine or squarewave, then I find I'm unable to figure out the reason.

--------

In the US we use 2-phase 120VAC. Each house has two independent branches carrying mains power. Hence it is easy to attach certain circuit-breakers to one branch of mains, and the rest to the other branch. (This may not be possible in other parts of the world.) However it doesn't appear to solve your specification that the appliances we wish to power may be anywhere in the house, on any circuit breaker.

---------- Post added at 15:44 ---------- Previous post was at 15:25 ----------

Is it that sinewaves are hampered by something going on in the house? Resulting in great loss of efficiency and heavier battery use?

Or do sinewaves cause something to go wrong?

What about motors causing current lag, etc.? Causing changes of phase in the AC voltage? Resulting in shorts between appliances, or some other bad thing to happen elsewhere in the house?

Whereas square shaped waves do not create current lag, so no trouble in that regard.

If appliances really have been ruined by a sinewave inverter in such scenarios, then that is something that would convince me to install a modified sine (squarish waves) inverter.

Hi Brad... Since you took time in analysing what could be the answer, I guess it is time I give it... tataaaaa... :-D

The big difference between the sinewave and modified sinewave shapes makes possible to build a very simple relay controller (hence low cost) that activates a relay when the supply voltage is sinusoidal and keep it off if rectangular.

Therefore, if the emergency power is also sinusoidal, the solution should be professional. For example, a pilot signal could be added to the inverter output, so that the relay controller will connect the power line only if it doesn't detect the presence of this pilot. Naturally, if I own a big company (not my actual small one :roll: ) producing high quality inverters (hence of sinewave type), I certainly add this feature (likely as an option) and provide controllers with different powers that are compatible to my products.

Back to reality, by providing a simple low cost solution to isolate automatically any appliance (or a group of appliances), many houses don't mind installing the less professional inverter as the modified sinewave type. Otherwise their whole power installation should be revised if things need to be automatic and reliable.

Kerim

I get it. Very ingenious. I would never have thought of it. It gives you a price advantage over your competitors.

The shape of the incoming power is able to tell this or that appliance to stay off.

You do not need to inject a 'stay-on' signal into the power lines. Your sense modules do not need special circuitry to interpret those command signals.

The sense modules are low cost so it is economical to put one on every appliance that you want to keep turned off during blackout.

Hi again,

Here is the rest of the story :wink:

First, where it happens I live and work, I cannot get all components to produce (and the tools to design) what I may have in mind. So making reliable sinewave inverters is out of question on my side.

Second, many around me were proud with their sinewave inverters bought from abroad telling me that modified sinewave inverters cannot be considered by serious people anymore.

So, providing the simple low cost controller (RC and transistors) helped me defend my position... so far :smile:

Kerim