SINUS INVERTER PROJECT

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Albert H
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Re: SINUS INVERTER PROJECT

Post by Albert H » Tue Jun 28, 2022 2:00 am

MIND YOUR FINGERS! 240V AC really bites hard!
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Tue Jun 28, 2022 11:48 pm

Albert H wrote:
Tue Jun 28, 2022 2:00 am
MIND YOUR FINGERS! 240V AC really bites hard!
Haha! It certainly is a mistake that you never forget!! :lol:

The trailing socket makes connecting appliances much safer with the top cap fitted, Less fiddling with Live cables!

Also your comment Albert raises some good points when dealing with this type of Inverter?

The transformer isolates the output from "Earth" or any other common Ground? So in theory? I would need to be in contact with both the Live and Neutral to receive a shock? (I will not be testing this theory in any case :lol: ) Which is not true of the Domestic Mains!

Anyways the system will need to be "Earthed" one way or another? In the case of Batteries, Solar or other forms of power generation, There is not really provision for "Earth" available?

The only sure way i know of is a Rod driven into the physical Ground! (Beneath our feet) Or connection to an existing "Earth" installation?
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Wed Jun 29, 2022 12:02 am

Anyways, Here is the actual Output of the Inverter!
Inverter Output.PNG
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Wed Jun 29, 2022 12:07 am

The above is the Waveform unloaded and attenuated to read on the Scope!

The Output filter is far from perfect? But seems to be cleaning up some of the spikes and ringing that was previously present?

Frequency remains stable @ 48.84 Hz!
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Wed Jun 29, 2022 12:26 am

So far so good! :)

I now need to focus on a feedback system to keep the output voltage in check!

I see 3 possible ways of doing this?

An Opto Coupler from the Live side to retrieve a DC signal?

A miniature transformer from the Live side to retrieve the same?

Or an Auxillary winding wrapped on the Toroidal transformer to sense changes in voltage?

The third option seems to be the simplest? So i may experiment with that first?
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Re: SINUS INVERTER PROJECT

Post by radium98 » Wed Jun 29, 2022 5:32 pm

Opto Coupler from the Live side to retrieve a DC signal?

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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Sat Jul 02, 2022 11:01 pm

Back again! :)

I decided to put the Inverter into LTSpice to perform some simulations? However, I have been having trouble getting the transformer to function correctly? But i will work it out!

Here is the schematic below!
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Sat Jul 02, 2022 11:02 pm

Schematic.PNG
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Sat Jul 02, 2022 11:21 pm

As you may notice? The crystal time base has been omitted!

This is because LTSpice does not have the 4060 and 4013 in the library of components!

V1 and V2 represent the time base and deliver pulses to the Mosfets (M1 and M2) which drives the transformer @ 50 cycles per second!

I also added two additional Mosfets (M3 and M4) which will be controlled by the Feedback circuit!

M3 and M4 will be in a fully ON state by default and react to Feedback changes if everything works as planned?
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Sun Jul 03, 2022 11:09 pm

So! I managed to get the Transformer issues sorted!

It turns out i had messed up the inductance values! :lol: Also due to the heavy currents involved, The Fets needed a bit more Gate drive!

The circuit fired up as expected! :)

Tests below!
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Sun Jul 03, 2022 11:11 pm

Inverter 1.PNG
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Sun Jul 03, 2022 11:30 pm

Now that it is working as it should, I will add the Feedback control and see how it performs! :)
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Mon Jul 04, 2022 11:12 pm

So here is quick example of Feedback using an Opto coupler!

The high voltage side is isolated from the low voltage side which is good!

The Feedback voltage also tracks the output but only by a small amount? I believe this is due to the Opto coupler being saturated?

More adjustments need to be done? Heres the schematic below! :)
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Mon Jul 04, 2022 11:18 pm

Inverter Feedback.PNG
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Mon Jul 04, 2022 11:43 pm

As can be seen, It is very basic for now!

The Opto coupler is currently using only Half Wave rectification which will cause inbalances on the output!

This also effects the DC to the Fets which is smoothed to a certain extent by C2!
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Tue Jul 05, 2022 12:12 am

Also just to explain briefly how it works for those who are a bit confused?

When the circuit starts up, There is no output voltage! This means that the Opto coupler is off and the Fets M3, M4 are switched fully on!

As the output voltage starts up? The Opto coupler will begin to activate bringing M3, M4 into a perpetual conduction!

Which basically means that when the output voltage tries to rise? It will be pulled down and Vice Versa!

I hope that makes sense? :lol:
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Re: SINUS INVERTER PROJECT

Post by Albert H » Tue Jul 05, 2022 1:36 am

Sinus - your feedback scheme isn't likely to work too well - the opto-coupler isn't a "linear" type, it's either on or off (though it does have a very small, almost linear "transition" curve in part of its conduction characteristic). If you want analogue control of the output voltage, you need to use some kind of linear feedback. I used a component called an LCR0202 which is a linear opto. The output side of it is a photoresistor, and the input is an LED. The linear range is fairly big, and if you use a bridge rectifier feeding the LED side, you can monitor the whole waveform.

Modern inverters are usually based on PWM generation - the mark / space ratio of the switching signals is used to vary the power delivered. This can also allow very high conversion efficiency.
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Tue Jul 05, 2022 11:21 pm

Albert H wrote:
Tue Jul 05, 2022 1:36 am
Sinus - your feedback scheme isn't likely to work too well - the opto-coupler isn't a "linear" type, it's either on or off (though it does have a very small, almost linear "transition" curve in part of its conduction characteristic). If you want analogue control of the output voltage, you need to use some kind of linear feedback. I used a component called an LCR0202 which is a linear opto. The output side of it is a photoresistor, and the input is an LED. The linear range is fairly big, and if you use a bridge rectifier feeding the LED side, you can monitor the whole waveform.
Cheers Albert! :)

My experience with Opto Couplers is limited! And what you said would explain why the response of the feedback is lacking!

The LCR0202 is not included in the library? But there may be something similar i can experiment with?

Also the Opto Coupler is not the only option i plan to try? :)
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Re: SINUS INVERTER PROJECT

Post by sinus trouble » Tue Jul 05, 2022 11:51 pm

Albert H wrote:
Tue Jul 05, 2022 1:36 am
Modern inverters are usually based on PWM generation - the mark / space ratio of the switching signals is used to vary the power delivered. This can also allow very high conversion efficiency.
They do indeed! :)

I could go down the route of PWM controllers, High frequency transformers and H Bridges Etc....

The aim of this project is to build something half decent without the use of specialised components?

Something you could "Knock up" out of junk shall we say?

Something you could use in an emergency? :)
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Re: SINUS INVERTER PROJECT

Post by Albert H » Wed Jul 06, 2022 3:55 am

I'll dig out my notes on Inverter feedback control, and put it up here later.
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