Power Inverter Project .................

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i have made a power inverter circuit using arduino uno. Arduino is generating 5V 50hz square wave which is further converted into 12V using L293d to feed mosfet. well i am confused what transformer and mosfet be used here as i am aimed to built a inverter of 230V 350watt.what should be rating of step up transformer. i have 12V battery.also tell me if there is something missing in circuit like resistor somewhere etc......

 

 

 

then someone told me that l293d drive too much less current to mosfet so use l298...... i used that

 

now tell me if there is a mistake or there is lack of any component like resistor capacitor or diode......

also tell me the right mosfets for generating 350watts......

and the transformer ratings......

is irf3205 good for 350watts...

I am a Learner

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The Snakes and Ladders game is started.!

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Use mosfet driver chips rather than motor driver bridges. Something like a tc4427.
It diesn't look like tou have incorporated dead time between your phases. This might cause some losses.
You might want some snubbers to cope with leakage inductance.
As for the transformer - 18V centre tapped with >350W.

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i have checked in proteus .... it  has tc4427 and tc4424...... tc4427 has 1.5amps and tc4424 has 3amps...... 

which should i choose

 

I am a Learner

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Which one did I suggest?

The IRF3205 is a bit low in voltage - you'll need to design your snubber carefully. You'll also need to calculate how much loss in the the mosfet and whether you need to heatsink it. Hopefully proteus will assist in the simulation.

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i had studied the data sheets of tc4424 and tc4427....... tc4424  is newer version of other and hence more reliable..........so i made changes by replacing the l298 with microchip driver.

 

now suggest the mosfet.....

irfz44n is for 200 watts.

any other?

 

*and you also said to study energy losses in circuit...... i noticed people saying to place resistors and diodes around mosfets ..... i have no idea about that.... could you comment in this topic.

*and as i have 12v battery, i am confused , i should use 12-0-12 transformer or 18-0-18 as you suggested.

I am a Learner

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18V centre tapped is 9-0-9. Why 9V? Peak vs rms.
How is the irfz44 higher voltage?

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I am confused too. I don’t know the voltage of motor?

I Don’t know voltage of power supply?
Do you intend to rotate in one direction?

Is It important for you ,  accelerate and decelerate

Do you have PID feedback?

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Ahsan Ali wrote:
Arduino is generating 5V 50hz square wave

That is really not a good idea.

 

You will get problems with saturation in the transformer core.

 

https://en.wikipedia.org/wiki/Power_inverter#Square_wave

 

You do realise that 350W at 12V is nearly 30 amps - don't you ?!!

 

surprise

 

Working at that kind of power requires very careful design - this is not a beginner's project!

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Goorman wrote:
I don’t know the voltage of motor?

It's not a motor - it's an inverter.

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Goorman wrote:
motor

 

The OP did not say motor. Kartman said correctly that the L293D is a "motor driver bridge" IC and that the OP should not use it for this type of application.

Ross McKenzie ValuSoft Melbourne Australia

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Really?
I totally lost my mind
Yes , he's talking about  inverter. !!!!blush

 

edit:

 ok, I got it.

the ICs  made me wrong.

350w 50Hz inverter from 12vDc.

The core will be very large and there will be harmonies too.

Change your route and go to high frequencies.

 

 

Last Edited: Mon. Aug 21, 2017 - 12:09 PM
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First, from what I guess of your level of experience with electronics you probably should not (yet) be messing with thesee voltages / power levels.

On the other hand. smoke is fun too.

 

Recently I was on the site of ST for STM32 range of uC's.

They had a few application notes with reference designs for inverters from solar to deliver back to te power grid.

Complete with schematics, source code & pcb's.

You might want to study them.

Atmel / Microchip praobabl als has similar application notes.

 

But why bother at all?

Circuits like these are quite hard to design properly and cheap to buy.

And they often come in a nice aluminimum enclosure which alone would be a sustantial part of your budget.

 

Paul van der Hoeven.
Bunch of old projects with AVR's:
http://www.hoevendesign.com

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Paulvdh wrote:
Circuits like these are quite hard to design properly 

Indeed.

 

You need some pretty solid electronics expertise and experience.

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well ok. i am giving up.

I am a Learner

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Circuits like these are quite hard to design properly

     Are quite hard to see  when your money are dancing  like smoke in the air.

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Paulvdh wrote:
First, from what I guess of your level of experience with electronics you probably should not (yet) be messing with thesee voltages / power levels. On the other hand. smoke is fun too.

 

Apart from the joking about smoke from Paul here, there is the serious side of this to consider. As always, when it comes to amateurs trying to deal with high energy stuff:

 

1) Do not sell it or let anyone else come near it.

 

2) Realize that you can die - if you're lucky it will be swift. If you're less lucky it will be painful, possibly very painful. If you're unlucky you will not die but become an invalid of some sort. 

 

3) If you are (part of) family support, make sure you have insurance covering your death due to ignorance.

 

4) Also consider the risk of fire, so make sure you have house insurance covering fire due to ignorance.

 

None of the "ignorance" stuff above is to be taken as derogatory. It is about actually not knowing what you are doing, the risk yo are taking and the consequences of it.

 

I'm just as ignorant about these matters and am not afraid to admit it. I stay away from high voltage stuff, with the exception of where I have a solid design from someone I trust and where knowledgeable people can vouch for it [1]

 

Re 3) perhaps also tell your partner that you are taking a risks and might die doing it. Talk through the insurance terms so that your partner is prepared if things come to the worst.

 


 

[1] In my case a few valve/tube amplifiers. I did this with a friend, and we had rules set up that we vowed to follow - something like:

 

- Never work alone. Always two. Only one of us actually doing things, the other one a security/rescue person.

 

- Don't touch amp with both hands, if avoidable. Other hand on lower back tucked under belt to avoid reflex movements towards the amp.

 

- We had a "safe switch" that guaranteed that the supply voltage (with caps 4 x 47 uF at 250 V) was shortened to ground. Safety guy double-checked that it was active before allowing working guy to dig in. Safety guy always prepared to cut mains supply power instantly from a "safe station".

 

- Follow the design to the letter. No experimenting! 

 

In case you're curious: http://ax84.com/p1.html , and especially have a look at http://ax84.com/hivoltage.html :

 

WARNING! - Please Read this Information Carefully:

The projects described in these pages utilize POTENTIALLY FATAL HIGH VOLTAGES. If you are in any way unfamiliar with high voltage circuits or are uncomfortable working around high voltages, PLEASE DO NOT RISK YOUR LIFE BY BUILDING THEM. Seek help from a competent technician before building any unfamiliar electronics circuit. While efforts are made to ensure accuracy of these circuits, no guarantee is provided, of any kind!

"He used to carry his guitar in a gunny sack, or sit beneath the tree by the railroad track. Oh the engineers would see him sitting in the shade, Strumming with the rhythm that the drivers made. People passing by, they would stop and say, "Oh, my, what that little country boy could play!" [Chuck Berry]

 

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

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An  often overlooked safety tip:

Never work alone & let the other guy turn it on.

When in the dark remember-the future looks brighter than ever.

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Ahsan Ali wrote:

Arduino is generating 5V 50hz square wave

 

That is really not a good idea.

 

You will get problems with saturation in the transformer core.

 

https://en.wikipedia.org/wiki/Power_inverter#Square_wave

I'm puzzled by your comment, are you saying that transformers don't like square waves?  For most of the last hundred years almost all inverters were transformers being driven by square waves.  Actually, many inverters are still driven with square waves, especially the gazillion consumer ups out there.

 

Tom Pappano
Tulsa, Oklahoma

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looking at the posted waveforms, the Arduino was generating pwm. So that basic concept wasn't too bad. In terms of a learning project, there are a few challenges. Notwithstanding the safety aspect - the voltages involved can kill, mosfets exploding can injure your eyes and the high currents involved can cause fires. As a kid I played around with similar devices and lived to tell the tale. Even as an 8 year old I was keenly aware of high voltage. Not so aware of things going pop! But I learnt quickly.

 

The challenges with this kind of circuit are:

1. High currents. 30A was mentioned. This means you would want to understand wire sizing and fusing. 

2. sizing of the mosfets. 55V is probably not adequate for this application. I'd suggest 100V or more.

3. wiring of the mosfets - 30A is a challenge. Every piece of wire is a resistor and inductor.

4. heatsinking of the mosfets. At 8mOhm and 30A, the drop across the mosfet is V=I x A = 0.008 times 30 = 0.240V. Watts = I x V = 30 x 0.24 = 7.2W. Without heatsinking the mosfet will last a couple of seconds. "But the datasheet says 200W" - yes, but the datasheet also tells us the J/A C/W is 62 so 7.2W times 62 is 446.4 degreesC. We've exceeded the temperature spec, so we clearly need a heatsink.

5. We would probably want two or more mosfets in parallel to cut down the losses.

6. We'd want a snubber across the transformer as we've using pwm and there will be some flyback energy. This is where is gets nasty. A good simulator can help here but you'll also need an idea of the transformer parameters which normally aren't specified. There's no substitute for experience and theory here. Mistakes here usually mean the mosfets will randomly fail.

7. dead time for your mosfet drive. The mosfets take a finite amount of time to turn on and off. You don't want to have the other side turn on whilst the other is just turning off. Dead time is the period between turn off on one side and turn on on the other. Get this wrong and again the mosfets will either fail quickly or you'll get bad efficiency and the mosfets die randomly.

 

How does one design something when they have NFI? Look at a design that works. Understand the design decisions, then attempt your own. 350W inverters a quite cheap out of China. I bought a 'true sinewave' one for $50USD. The effort and parts cost to design and build something similar is way in excess of that price. I wanted to see how they designed it. As mentioned by others, there are app notes on various inverters for solar from the likes of Microchip and others. uninterruptible power supplies for PCs are dime a dozen. They blow up when the batteries get low, so it is cheaper to buy a new one. These are highly cost engineered products, so if they use two mosfets instead of one - then there's a very good reason. Also be aware that the electronics in these can be live, so be careful where you touch.