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Modified sinewave to pretty good sinewave?

HANKMARS

Jul 28, 2019
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I have a decent 1100 watt modified sinewave invertor. 12 VDC to 120 VAC. Nice readout, input volts, Iout, couple warning prompts. If you have seen modified sinewave output then you are aware that it is mostly square wave with 4 shoulder levels per cycle. Pretty cheesy. Good for purely resistive load but hell on anything with windings. IF, I put a couple 25000 ufd 250 volt caps in parallel with inverter Vout, will I see something more closely resembling a sinewave? Say pulling about half capacity, around 500 W?
 

Bluejets

Oct 5, 2014
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All that does, assuming the correct type of capacitor, will be to slightly change the power factor.
AC does not follow any DC specs.
 

HANKMARS

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All that does, assuming the correct type of capacitor, will be to slightly change the power factor.
AC does not follow any DC specs.
How about if I put a cap on each side of neutral or ground, and store a sinewave pattern in ram memory and clock thru memory at the appropriate speed that will give me 60 Hz or rather clock thru memory at 0.0166 seconds then back to memory start address?
 

HANKMARS

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I am open to any suggestions as how to manipulate this corrupt waveform into something that won't fry motors, transformers and the like.
 

Bluejets

Oct 5, 2014
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Take an engineering degree and design and build to new outcome specs.
Make sure you have a few million bucks spare to cover research and development.

Or just buy the correct type, the latter would be the option most would go for.
 

HANKMARS

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Take an engineering degree and design and build to new outcome specs.
Make sure you have a few million bucks spare to cover research and development.

Or just buy the correct type, the latter would be the option most would go for.
Stuff's not getting any cheaper. It is nice to be able to modify salvage. Most always for my own use. Frivolous law suits and such. I think I'll go with the sinewave code in memory which feeds a D/A converter which drives the base of a power transistor. Knocking the efficiency even lower but if I can get 1100 watts for 40 dollar, so be it. Misread description on 2200 watt inverter that turned out to be 220 VAC. Ordered appropriate buck/boost tranny. Shipping tracking showed it made it to my town but then became "lost." Seems impossible in a little burg of less than 3000 people.
 

Harald Kapp

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I think I'll go with the sinewave code in memory which feeds a D/A converter which drives the base of a power transistor.
There's more to it than simply driving the power transistor(s) by a sinusoidal base drive. As it is, the "modified sine wave" is likely to be created by using the transistors as switches (which is why you see a mostly rectangular waveform). Power dissipation in a switch is very low.
When you use the transistor as an analog driver, power dissipation will increase considerably. Assuming the transistor supports this mode of operation at all, you will need to add a massive heat sink, possibly even cooling fans.

This is not how a "pure sine wave" inverter works.

A "pure sine wave" inverter, too, uses the transistors as switches. It approximates the sine wave by using modulated PWM (link). Thus power dissipation in the transistors is greatly reduced.
 

kellys_eye

Jun 25, 2010
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You can purchase a pure sinewave gasoline genset for a lot less trouble and cost of designing/modifying a modified sinewave device.

Since your inverter requires a battery input (supply) and gasoline is orders of magnitude better at energy storage than batteries, why bother? That said, I use a pure sinewave inverter for temporary (very) occasions and only for minimal loads. I also have two 750W and one 3kW pure sinewave inverter generators for when the power really goes out - as may well be happening across many countries this winter.

PS - I have a spare 3kW charger/controller/inverter (pure sinewave) you can have FOC for the cost of postage - weighs 55kg.
 

HANKMARS

Jul 28, 2019
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You can purchase a pure sinewave gasoline genset for a lot less trouble and cost of designing/modifying a modified sinewave device.

Since your inverter requires a battery input (supply) and gasoline is orders of magnitude better at energy storage than batteries, why bother? That said, I use a pure sinewave inverter for temporary (very) occasions and only for minimal loads. I also have two 750W and one 3kW pure sinewave inverter generators for when the power really goes out - as may well be happening across many countries this winter.

PS - I have a spare 3kW charger/controller/inverter (pure sinewave) you can have FOC for the cost of postage - weighs 55kg.
I am interested in 3 kW unit but also guess shipping cost may be prohibiting. Common carrier would be my choice. I would need pick up address (residential or business area), ( loading dock, yes or no ), I could then get quote from truck broker. I recently purchased an Onan gasoline/propane fuel generator, 3000 W, 1800 rpm.
 

HANKMARS

Jul 28, 2019
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You can purchase a pure sinewave gasoline genset for a lot less trouble and cost of designing/modifying a modified sinewave device.

Since your inverter requires a battery input (supply) and gasoline is orders of magnitude better at energy storage than batteries, why bother? That said, I use a pure sinewave inverter for temporary (very) occasions and only for minimal loads. I also have two 750W and one 3kW pure sinewave inverter generators for when the power really goes out - as may well be happening across many countries this winter.

PS - I have a spare 3kW charger/controller/inverter (pure sinewave) you can have FOC for the cost of postage - weighs 55kg.
I will soon be living off grid. Access to clean water is paramount. No water, no life, no need of electricity. Currently have solution to water needs. In a prior off grid living situation, I found it to be disturbing to run a gasoline powered generator to merely watch movies on a tv or monitor. A rather gross waste of resources. Hence, I thot it prudent to store energy by means of gravitational potential energy. An idea found laughable by most here and in the physic's forums. I believe that comes from their misunderstanding of grav-poten formulas. I can easily raise a 1 tonne mass 3 meters in less than 5 minutes with a meager gas powered generator. Extracting the potential energy by means of controlled decent, I can easily produce enough energy to power media players for hours. It is a necessity to develop a "don't give a rodent's posterior" attitude towards the nay sayers but that needs to be tempered with knowing when to listen.
 

HANKMARS

Jul 28, 2019
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There's more to it than simply driving the power transistor(s) by a sinusoidal base drive. As it is, the "modified sine wave" is likely to be created by using the transistors as switches (which is why you see a mostly rectangular waveform). Power dissipation in a switch is very low.
When you use the transistor as an analog driver, power dissipation will increase considerably. Assuming the transistor supports this mode of operation at all, you will need to add a massive heat sink, possibly even cooling fans.

This is not how a "pure sine wave" inverter works.

A "pure sine wave" inverter, too, uses the transistors as switches. It approximates the sine wave by using modulated PWM (link). Thus power dissipation in the transistors is greatly reduced.
I have downloaded the link from TI. Will spend some time with it, am sure. Thanks. The PWM to MOSFET switches used in high power situations is something I need to get my head around. It really is the preferred method, I must assume. You are correct about the power dissipation of a power transistor being operated as an A class or AB class high power device. It can literally become a red hot "smoking" idea. Push/Pull configurations are an improvement, but still.....
 

kellys_eye

Jun 25, 2010
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You never get more out than you put in so using a motor to lift something that drops to generate power is a pointless waste of time/resource although it's neither my time nor my resources so fill your boots!

The best situation for off grid would be anywhere you can utilise water flow - hydro (micro hydro in particular) - but obviously solar PV works for some and so does wind.

I've arranged my own home to be capable of running on 300W of electricity (max 500W) and that covers essential lighting, comms (internet) and entertainment (TV/lapdog). This is currently via the aforementioned inverter-generator that runs for 8+ hours at a 500W load on a 5 litre tank of petrol. We otherwise have a woodstove (I live in a forest) for all heating, a fresh water loch (with fish), private water and sewage facilities, hunting (if necessary), local farmers with livestock and facilities for growing food.

Personally I'd use solar except for the distinct lack of sunlight in Scotland! Oh, we get some, but not reliably and it certainly wouldn't pay for itself in its lifetime but when it's a case of some electricity or no electricity your options are decided for you!

There are many, many people I know looking for a lifestyle like mine (or yours) and we get loads of enquiries from customers asking if there are any properties for sale - short answer, no. Given the current situation I have no intention of letting what we've developed and created go to waste.
 

Bluejets

Oct 5, 2014
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Hence, I thot it prudent to store energy by means of gravitational potential energy. An idea found laughable by most here and in the physic's forums. I believe that comes from their misunderstanding of grav-poten formulas. I can easily raise a 1 tonne mass 3 meters in less than 5 minutes with a meager gas powered generator. Extracting the potential energy by means of controlled decent, I can easily produce enough energy to power media players for hours. It is a necessity to develop a "don't give a rodent's posterior" attitude towards the nay sayers but that needs to be tempered with knowing when to listen.

And the soothsayer hath spoken.........:rolleyes:
 

HANKMARS

Jul 28, 2019
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You never get more out than you put in so using a motor to lift something that drops to generate power is a pointless waste of time/resource although it's neither my time nor my resources so fill your boots!

The best situation for off grid would be anywhere you can utilise water flow - hydro (micro hydro in particular) - but obviously solar PV works for some and so does wind.

I've arranged my own home to be capable of running on 300W of electricity (max 500W) and that covers essential lighting, comms (internet) and entertainment (TV/lapdog). This is currently via the aforementioned inverter-generator that runs for 8+ hours at a 500W load on a 5 litre tank of petrol. We otherwise have a woodstove (I live in a forest) for all heating, a fresh water loch (with fish), private water and sewage facilities, hunting (if necessary), local farmers with livestock and facilities for growing food.

Personally I'd use solar except for the distinct lack of sunlight in Scotland! Oh, we get some, but not reliably and it certainly wouldn't pay for itself in its lifetime but when it's a case of some electricity or no electricity your options are decided for you!

There are many, many people I know looking for a lifestyle like mine (or yours) and we get loads of enquiries from customers asking if there are any properties for sale - short answer, no. Given the current situation I have no intention of letting what we've developed and created go to waste.
I do believe Scotland would be one of the few places I would thoroughly enjoy visiting. Should I ever have to tolerate a monetary windfall, I may request your assistance in recommended highlights to visit, when I am not in the pubs. Regarding conservation of energy: The values in the following text are mostly WAGs, or more so maybe SWAGs (Scientific Wild Ass Guesses). Let's assume I have a forklift capable of raising a 1 tonne mass, 3 meters, in 10 seconds. The forklift has, of course, governors (mechanical or electronic) that will adjust fuel intake according to the load upon it. Again, I'll guess that 80 horse power along with the mechanical advantage of a hydraulic system, will raise my mass, 3 meters in ten seconds. Assuming that these figures were correct and that the least power needed from the forklift engine is 80 hp, then the following formula (somewhat corrupted), apply. Convert 80 hp applied for a 10 s burst to joules. Convert that value to kWH. Divide that value by my continuously applied load of 250 W. Continuous load of 250 W will equal 0.25 kWH usage. With that value known, I can now calculate the time period for which my 250 W load will operate. Let's guess that my mechanical energy storage device has an efficiency of 50% (friction, REMF, whatnot). From previous calcs I have done, the potential energy of this rock battery (converted) should power my 250 W load for 16 hours. The one thing missing in this endevour before I start construction, is a mathelete. U (the change in potential energy) = m ( IN grams, { this is where the non-serious mathematician flounders }) times g ( gravitational force approx 9.8 ) times h ( height in meters to zero point { Earth surface }). U=mgh. Most will use the accepted international units of kilograms ( kg ) to do the calcs. Their results are then skewed by a factor of 1000. Generally the assumed result is 0.0087 kWH of potential energy available from a 1 tonne mass suspended 3 meters above the surface. So, if that figure were correct and considering what you brought up about conservation of energy, there is enough energy stored in 3 AA batteries to raise 1 tonne 3 meters. I can not accept that. I am willing to be proved wrong here, but have not yet encountered a believable argument.
 

kellys_eye

Jun 25, 2010
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So, if that figure were correct and considering what you brought up about conservation of energy, there is enough energy stored in 3 AA batteries to raise 1 tonne 3 meters. I can not accept that.
1hp is 736W and can lift 75kg 1 metre in 1 second (wikipedia).

Using maff - 1000kg would be raised 1 metre in 13.3 seconds (1000/75) using 736W and take 40 seconds to reach 3 metres.

A typical alkaline AA battery has a capacity of 3.9Whr so three of them would have 11.7Whr. Divide the 736W by 11.7 you get 63 and multiply by the 40 seconds = 2516 seconds or about 42 minutes to take 1 tonne 3 meters vertically.

Notably the 42 minutes is within the 1 hour rating of the batteries and, as ever, this all assumes 100% efficiency in all moving parts AND the required torque/gear reduction system (loss-less).

Clearly the 100% efficiency (or loss-less) aspect is the killer and makes the difference between believable and 'impossible' - but, in THEORY, yes you can use 3 AA batteries to lift 1 tonne 3 metres.

Give this 'truth' your raised weight can only return the same energy when it falls (less given the system losses in falling) so the maff holds up as does the impracticality of it all.
 

HANKMARS

Jul 28, 2019
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1hp is 736W and can lift 75kg 1 metre in 1 second (wikipedia).

Using maff - 1000kg would be raised 1 metre in 13.3 seconds (1000/75) using 736W and take 40 seconds to reach 3 metres.

A typical alkaline AA battery has a capacity of 3.9Whr so three of them would have 11.7Whr. Divide the 736W by 11.7 you get 63 and multiply by the 40 seconds = 2516 seconds or about 42 minutes to take 1 tonne 3 meters vertically.

Notably the 42 minutes is within the 1 hour rating of the batteries and, as ever, this all assumes 100% efficiency in all moving parts AND the required torque/gear reduction system (loss-less).

Clearly the 100% efficiency (or loss-less) aspect is the killer and makes the difference between believable and 'impossible' - but, in THEORY, yes you can use 3 AA batteries to lift 1 tonne 3 metres.

Give this 'truth' your raised weight can only return the same energy when it falls (less given the system losses in falling) so the maff holds up as does the impracticality of it all.
Let me think out loud here so that my errors can be rubutted. 75 kg = 0.075 tonne. 1 hps can raise 0.075 tonne 1 meter. 1000/75. 1 hp will require 13.3 seconds to raise tonne one meter or put 13.3 hps. So right, 40 hps will raise 1000 kg 3 meters. Or 736 watts applied for 40 seconds equals 736 Ws or 736/3600 = 0.20 WH. 0.20/ 1000 = 0.00020 kWH. Seems ballpark. A 7 A, 110 V motor raising a tonne 3 meters in 40 seconds. I can visualize that. My favorite rechargeable cells deliver 2.8 AH. It can deliver 1.2 V times 2.8 A = 3.36 watts for an hour. That is 0.00336 kWH. Times 3 equals around 0.010000 kWH. 0.01000/0.00020 = 50. In theory, I can raise a tonne 150 meters, about 500 ft, straight up with 3 AA batteries. Impressive. The trouble with modified sinewave ( a totally bogus term IMO ) is the long duration at full voltage tends to over heat windings, burning of the lacquer insulation resulting in shorted coils. I quite possibly made a mistake in the above calcs and appreciate an explanation of my errors.
 

HANKMARS

Jul 28, 2019
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Let me think out loud here so that my errors can be rubutted. 75 kg = 0.075 tonne. 1 hps can raise 0.075 tonne 1 meter. 1000/75. 1 hp will require 13.3 seconds to raise tonne one meter or put 13.3 hps. So right, 40 hps will raise 1000 kg 3 meters. Or 736 watts applied for 40 seconds equals 736 Ws or 736/3600 = 0.20 WH. 0.20/ 1000 = 0.00020 kWH. Seems ballpark. A 7 A, 110 V motor raising a tonne 3 meters in 40 seconds. I can visualize that. My favorite rechargeable cells deliver 2.8 AH. It can deliver 1.2 V times 2.8 A = 3.36 watts for an hour. That is 0.00336 kWH. Times 3 equals around 0.010000 kWH. 0.01000/0.00020 = 50. In theory, I can raise a tonne 150 meters, about 500 ft, straight up with 3 AA batteries. Impressive. The trouble with modified sinewave ( a totally bogus term IMO ) is the long duration at full voltage tends to over heat windings, burning of the lacquer insulation resulting in shorted coils. I quite possibly made a mistake in the above calcs and appreciate an explanation of my errors.
Wait. That should be 736 watts delivered for 40 seconds = ? kWH
 

HANKMARS

Jul 28, 2019
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0.01000/0.00736 = 1.3 x 3 = 3.9 meters. Looks like it proves out.
 
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