250 to 5000 Watts PWM DC/AC 220V Power Inverter

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Introduction: 250 to 5000 Watts PWM DC/AC 220V Power Inverter

This is a heavy duty design of a Pulse Width Modulator DC/AC inverter using the chip SG3524 .
I've been using it as a backup to power up all my house when outages occur since aprox. 6 years non stop.

If you like the work and intend to build the circuit don't forget to click on the "I made it" button so I know how many people benefit from the design, Thanks.

Notes:

1> The schematic circuit design is for a 250 watt output, while the pics are of my 1500 watts inverter that i built, to increase the power of the circuit you have to add more of the Q7 and Q8 transistors in parallel, each pair you add will increase your power by 250 watts, ex: to get 750 watts of power from the inverter you need to add in parallel 2 of Q7 and 2 of Q8 to the original design.

2> If you increase the power transistors you have to enlarge the T2 transformer to match the new needs, the circuit's transformer is rated 25 amps to handle 250 watts of 220v, for every 1 additional amp you need on the 220v side you have to increase 10 amps on the 12v side, of course there are limits to the thickness of the winding so if you need more than 750 watts i recommend that you use a 24VDC supply instead of 12 volts:

DC voltage and Transformer "T2" size recommendation:
(Power) (Supply) (Transformer Winding)
(750w) (12VDC) (P:24V "12-0-12" / S:220V)
(1500w) (24VDC) (P:48V "24-0-24" / S:220V)
(2250w) (36VDC) (P:72V "36-0-36" / S:220V)
(3000w) (48VDC) (P:96V "48-0-48" / S:220V)
(3750w) (60VDC) (P:120V "60-0-60" / S:220V)
(4500w) (72VDC) (P:144V "72-0-72" / S:220V)
(5250w) (84VDC) (P:168V "84-0-84" / S:220V)
*The transformer should be "center tapped" at the primary side.
**You can make the secondary 110v if needed.
***The transformer in the pic is a custom made (48V center tapped / 220v ) 2000 watts, weights like 10 kilos.

Note15-Feb-16: (48V center tapped means: P:48V "24-0-24" / S:220V)

Note18-Feb-16: Test your transformer before doing this project. Disconnect the transformer from anything it is attached to, connect the 220v Secondary side directly into a 220vAC outlet and test the Primary side with your voltmeter, you should get exactly the voltage necessary for this project as per the table above. If not then don't waste your time building the project, it will not work.

****Do not supply the driver circuit with more than 24VDC max. because the voltage regulator "7812" will burn. Look at the pic of how to connect the batteries and where to take a 24vDC wire from.

3> R1 is to set the PWM duty cycle to 220v. Connect a voltmeter to the AC output of your inverter and vary VR1 till the voltage reads 220V.

4> R2 is to set the frequency to 50 or 60 Hz (R2 range is between 40Hz to 75Hz), so guys that do not have a frequency meter are advised to blindly put this variable resistor mid-way which should drop you in the range of 50~60 Hz.
If you want you can substitute the variable resistor with a fixed resistor using the following formula: F = 1.3 / (RxC)
in our case to get a 50Hz output we remove both the 100K and the variable 100K both from pin 6 and we put instead a 260K fixed resistor and we leave the 0.1uF (the 104 cap) as it is, this change should give out a fixed 50Hz as per the formula :
1.3 / (260,000 ohm x 0.0000001 farad) = 50Hz
But in reality it will not exactly give 50Hz because the 260K resistor has a specific error value margin so does the capacitor, that's why i recommend a variable resistor so that accurate calibration can be achieved.

5> Use either tantalum or polyester film "as in pic" for the 104 caps, ceramic disc caps are heat sensitive, they change value when hot and this in turn changes the frequency of the inverter so they are not recommended.

6> Pin 10 of the SG3524 can be used to auto shut down the inverter, once a positive voltage is given instead of negative to pin10, the SG3524 will stop oscillating. This is useful for persons wanting to add some cosmetic makeup to their inverter like "overload cut-off", "low battery cut-off" or "overheating cut-off".

7> Wiring connections on the power stage side should be thick enough to handle the huge amps drain from the batteries. I marked them with thick black lines on the schema also I included a pic so you see how thick those wires must be. (You can make the driving circuit section on a breadboard for testing purposes but NOT the power stage).

8> The design does not include a battery charger since each person will be building a custom version of the inverter with specific power needs. If you are ordering a custom made transformer you can ask them to take out for you an additional output wire on the primary side to give 14v (between point 0 and this new wire) and use it to charge a 12v battery, of course this needs a separate circuit to control charging auto cut-off. But anyway this is not advisable because it will shorten the life of the transformer itself since using it as a charger will toast the enamel coating layer of the copper wires over time. Anyway .. YES can be done to reduce cost.

9> A cooling fan will be needed to reduce heat off the heat sinks and transformer, i recommend getting a 220v fan and connecting it to the output T2 transformer, when you power up the circuit the fan will start this will always give you a simple way to know that 220v is present and everything is OK.. You can use a computer's old power supply fan if you like.
Note that the fan must suck air out from the inverter case and NOT blow inside, so install it the correct way or it will be useless.
Also note how I fixed both the heat sinks and where the fan is, in a way that the fan sucks hot air from like a channel between the 2 heat-sinks.

10> 2 circuit breakers are recommended instead of fuses, one on the DC side and one on the AC side, depending on your design
Ex: for a 24vDC ( 1500 watts design ) put a 60Amp breaker on the DC side and a 6Amp on the AC side.
For every 1amp of 220vAC you will be draining like 8 to 10 Amps from the 12v battery, make your calculations !

11> The 2 Heat sinks should be big enough to cool the transistors, they are separate and should NOT touch each other. "see the pics"

12>Important: If you're building a big design that uses more than 24VDC as power source, make sure not to supply the driver circuit with more than 24v maximum. (EX: If you have 4 batteries 4x12 = 48v , connect the v+ supply of the driver circuit to the second battery's (+) terminal with a thin 1 mm wire which is more than enough. (This supplies the driver circuit with +24v while supplies the power transformer with +48v) "see the batteries pic example"

13> "Optional" : Deep Cycle batteries are your best choice, consider them for best results .. read more

14> Be cautious when building this circuit it involves high voltage which is lethal, any part you touch when the circuit is ON could give you a nasty painful jolt, specially the heat-sinks, never touch them when the circuit is on to see if the transistors are hot !! I ate it several times :)

15> The optional "Low voltage warning" is already embedded in the PCB layout, you can disregard it and not install it's components if you do not need it. It does not affect the functionality of the main circuit, it just sounds a buzzer.

16> The Motorola 2N6277 is a durable heavy duty power transistor, it is used in many US tanks for it's reliability but unfortunately it is a very hard to find part, instead you can substitute each 2N6277 with 2 x 2N3773 or any equivalent, and yes equivalents work too.

17> I've included an optional "Battery level indicator" circuit diagram that has 4 LEDs, you can see it installed on the front panel of my inverter pic, it is functioning great and shows precisely how much juice the batteries still have. I have included a small relay that is powered by the last LED to auto shutoff the inverter once last LED is off.

Update 18-Feb-16: There are cheap readily available, professional looking Voltage, Current, Frequency Meter these days for a couple of $, consider them in your project. LED meter


18> Also included an optional "Overload circuit", it is very easy to build and can be calibrated to the desired overload current threshold cutoff point through the potentiometer VR1.
R1 is rated 5watts for inverters upto 1000 watts. For bigger versions of the inverter like 1000 to 3000 watts inverters, replace R1 (1 ohm, 5watts) with (1 ohm, 17watts) which should handle loads upto 10 VA.
Make sure you install a proper relay to handle big current drains.

19> Please guys take your time to read and understand my notes, browse and read the posts and questions asked by others because there are many useful information listed in replies. The main reason for me not answering your question is because it has already been asked before and answered upon.

20> It would be nice and inspiring for others if you take some photos and show us how you built your version, any additions to the circuit are mostly welcomed to be listed here, we can all benefit from them.

21> Please click on the "I've made it" button/icon if you did build the circuit so I know how many people benefit from this design.

22> Testing the circuit on a
breadboardwith crocodile clips or thin wires WILL NOT WORK ! You'll get wrong voltage readings. Don't come back crying that you're getting a 150vac output or so.

23> (20-Apr-2020) Why do we have a feedback voltage to T1 and R1? explained:

Let's presume we built a 12vdc/220vac inverter, we connect it to a 12vdc battery source and everything is working great.. we got ourselves a nice 220vac output. But what happens if the inverter is still running "ON" and we connect a charger to the batteries?? in other words we need the inverter to be always ON no matter the main electricity of the company is present or not, like we have some equipment that needs constant steady uninterruptible 220vac supply.

In this case: The 12vdc inverter gives out 220vac but when you turn on the charger the 12vdc will rise to 13.5vdc which reflects on the 220vac making it dangerously 248vac on the running equipment, here comes the function of the feedback section, it regulates the duty cycle that is generated inside the IC to maintain a steady regulated 220vac.

34 People Made This Project!

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1,895 Comments

0
CHARL1212
CHARL1212

2 months ago

Bjr, nick je veux savoir si c est possible d'utiliser deux circuit de sg3524 en parallèle pour augmenter la force du signal pr un inverseur de 10kva ou 20ka? Une réponse stp

0
Nick_Zouein
Nick_Zouein

Reply 2 months ago

Hi, no impossible, you can't use 2 driver circuits, there is no need.

0
olutayoofficial
olutayoofficial

Question 7 months ago

Hi Nick, I made the inverter, also made the battery Indicator, Overload protection with PC113, Battery charging circuit and Short circuit protection.

In the overload cut-off:
1. Where do I connect the circuit to PIN 10 of the IC?
2. Can I use PC113 Optocoupler in place of the MCT2E?

For the Optional filter:
1. Can I use 1uf 630v as a replacement for 0.1uf 600v?

Kindly respond.

0
Oroles
Oroles

Answer 4 months ago

Hello Olutayoofficial,
Until Nick will reply to you, I will try some answers for you:
1) If you will use the overload protection described here, with PC113, there is no need to connect it to the pin 10 of the SG3524. That's because there is a relay that will open the circuit through which the load is connected. The resistor R1 is a current transducer; when a current will pass though it, a voltage will appear at its terminals. That voltage will light the LED inside the optocopler.
So, for example, look in the table below, in which I calculated the power rating of R1 in respect to the power absorbed by the load resistance RL :
for RL=1000W -> R1=20W
for RL=500W -> R1=5W
for RL=300W -> R1= 1W
for RL=100W -> R1= 0.25W
You can calculate them very simple, using the Ohm Law: U=I*R and P=U*I .
2) I think that instead MCT2E, you can use almost any type of ordinary optocoupler (PC113, CNY17, 4N25...28, etc.).
3) For the optional filter, you must use the values provided in the schematic diagram (0.1uF and 2.2uF). The only think that you may replace, is the voltage rating, but always with a higher one. So you can use 0.1uF/800V or 2.2uF/1KV, but the effective values of the capacity must be respected .

I also have a question. You said you made the inverter. Did you build the version with BJT's or with MOSFET's ?

Best regards,
Dacian

0
olutayoofficial
olutayoofficial

Reply 4 months ago

Hi Dacian,

Thanks for your response. I actually built the inverter with MOSFET's as I had done in the past but using the IRFP250 image configuration, I successfully built the power stage.

However, I still have issues with the driver stage as the output voltage from PIN 11 and 14 is way higher than 2.5v even after replacing 7812 with 7808 as seen in one of nick's comment. I am trying to rebuild the driver stage again.

0
Oroles
Oroles

Question 4 months ago

Hi Nick, thanks for the previous reply!
I posted a return to your first reply, but I'm afraid you didn't notice, so I'm posting here again:

One more question, if you don't mind ...
Could you explain to me what is the role (the job) of the BC327 PNP transistor?
I can't understand how works that circuit ( I extracted it from your schematic and I attached it here).
Thank you in advance !
Best regards,
Dacian

BC327_NickZ.jpg
0
serkan_turkey
serkan_turkey

Question 1 year ago

can you explain the diode connection of the output of the power stage?

0
Nick_Zouein
Nick_Zouein

Answer 1 year ago

Dear Serkan_Turkey,
The diodes at the power stage act as filters eliminating any sparks or parasites in the waveform, you can remove them if you like, they are not necessary.

0
serkan_turkey
serkan_turkey

Reply 1 year ago

PWM output is changing like this after i connect the power stage to the driver stage. Could this breakdown be because I am not using diodes? And there is not output voltage at transfromer.

1.jpg4.jpg
0
Nick_Zouein
Nick_Zouein

Reply 1 year ago

What's the power source that you're using?

0
serkan_turkey
serkan_turkey

Reply 1 year ago

Seperately two power source for driver stage and power stage.

0
Nick_Zouein
Nick_Zouein

Reply 1 year ago

No this doesn’t work.

0
serkan_turkey
serkan_turkey

Reply 1 year ago

Thank you very much Nick, i will try with one power source. Is there any other mistake at this photo?

5.jpg
0
Oroles
Oroles

Reply 4 months ago

There is no mistake on your photo, but you must use a common ground at both power sources that you are using. Practically, you must link the (-) of the battery with the (-) of the power source that you are using for the PWM generator *AND* with the ground circuit on the PCB board.
If you will not link the negative poles between them and also with the ground of the PCB, the inverter will not work.
Good luck!

0
icaaci757
icaaci757

1 year ago

why my output voltage is so large, reaching 600 volts?

0
icaaci757
icaaci757

Reply 1 year ago

no electricity load

0
Oroles
Oroles

Reply 4 months ago

>> @icaac757: "no electricity load"
Impossible. The inverter has a feedback circuit, that is using the small 220V/12Vac transformer T1 (and also the diode bridge and the rest of the resistors till pin1 of the SG3524). From the R1 you may adjust the duty cycle (and in this way, the conduction of the power transistors) in respect to the voltage from the secondary of the T2 power transformer.
I think you're rather using a wrong type transformer for T2 !

0
Oroles
Oroles

Question 5 months ago

Hi Nick,
I am interested to build this inverter, but using mosfets, not bipolars.
Could you tell me please, if you practically built also a functional version with mosfets ?
In the hope of your answer, please allow me to congratulate you for your projects!
Regards from Bucharest,
Dacian

0
Nick_Zouein
Nick_Zouein

Answer 4 months ago

Hi Oroles,
Frankly no I didn't build a mosfets version but many other users did it successfully.
Browse the conversations and you'll find lots of useful info.

0
Oroles
Oroles

Reply 4 months ago

Good afternoon, Nick!
Thanks for your reply, I already read *all* the conversations ! :-)
One more question, if you don't mind ...
Could you explain to me what is the role (the job) of the BC327 PNP transistor?
I can't understand how works that circuit ( I extracted it from your schematic and I attached it here).
Thank you in advance !
Best regards,
Dacian

BC327-NZ_inverter.jpg