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 Battery level indicators these days for a couple of $, consider them in your project. LED meterLCD 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 150v output or so.

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1,870 Discussions

0
a58585
a58585

Question 22 days ago

I bought chinese one and when i connect the plus to the plus on the van and the minus to the minus on the van i run it and after a few minutes go back to the van and electrocute myself. the bloody thing makes electricity go everywhere and it is all just live. what is wrong?

0
Chizzie
Chizzie

Question 5 weeks ago

The transformer I got from an old UPS is not center tapped. Please i think I need a circuit diagram for that.

0
SujarW
SujarW

6 weeks ago

Do you have PCB design?

0
Rookie12345678
Rookie12345678

Question 8 months ago

where can I buy CT Transformer that is centre tapped on the primary side having the following specs. (750w) (12VDC) (P:24V "12-0-12" / S:220V)?

0
Nick_Zouein
Nick_Zouein

Reply 8 months ago

Hi Rookie12345678,
I don't think you'll find a ready made trans., you'll have to custom make it. Research your area on who custom makes such things.

0
reaganronald77
reaganronald77

Reply 8 weeks ago

Thanks @Nick_Zouein
I finally found one

0
RobinB56
RobinB56

Question 2 months ago on Introduction

what sized cap and resistor would it take to make it 60Hz?

1
wh1teshadow
wh1teshadow

Tip 3 months ago

Hi Nick, I advice you to use a low value 2-5 Watts resistor in series with each BJT's emitter pin to overcome the thermal solution. Because each of the parallelized BJTs has a different characteristic. One transistor would become too hot while the other stays cold or just getting warm.

I hope this would help to improve your circuit better.

1
PhilipB109
PhilipB109

3 months ago

Hi Nick.
Seeing that i'm not the sharpest pencil in the box...just one stupid question. The auxiliary transformer in your circuit, is that to control the output voltage.? Let's say i have 48volt setup but i connect the system to 60 volt will that control the output voltage to a standard 220volt or will I fry my trannies or something.? I want to use a 120v dc supply but i need to keep the primary very close to between 90 and 100volts.
Awaiting your response.

0
Nick_Zouein
Nick_Zouein

Reply 3 months ago

Hi PhilipB109,
No. If you have a 48v setup you can't connect to 60v. you'll burn the main transformer and probably all the power section.
The main purpose of the "auxiliary" transformer is to maintain a stable 110v or 220v output when a charger is charging the batteries.
ex: A 12v gives out 220v but when you turn on the charger the 12v will rise to 13.5v which reflects on the 220v making it dangerously 248v, here comes the function of the auxiliary.

0
Benit19
Benit19

Question 11 months ago on Introduction

Sir, what do you think about replacing the transistor in the power stage with IGBT? My project is to build 10 KW AC 240Volt

0
kennysoto47
kennysoto47

Answer 3 months ago

Hola bueno seria mucho mejor, pero desearía saber cuál es el Código del IGTB que lo vas a reemplazar, para calcular cuántos pares tendrías que poner ala etapa de potencia para obtener 10kw me puedes envíar al
kennysoto47@gmail.com

2
lannypks
lannypks

7 months ago

Hello Nick,
is PWM inverter same with pure sine wave inverter? and, can the power transistor be replaced with IGBT ? thanks

0
kennysoto47
kennysoto47

Reply 3 months ago

Hola amigo si se puede reemplazar los mosfet por igtv pero sería mucha fuerza con un par de mosfet estaría con 100w pero con IGTB sería el triple saludos

0
Mehrdad47
Mehrdad47

Question 4 months ago

Hello. Does this IC need special software?If so how can I get it Thanks.

0
Nick_Zouein
Nick_Zouein

Answer 4 months ago

no it doesn't

0
Mehrdad47
Mehrdad47

Reply 4 months ago

Very thanks

0
Dominicnze
Dominicnze

6 months ago

Hello Mr Nick, what are the voltages of the electrolytic capacitors in these schematics?

0
Nick_Zouein
Nick_Zouein

Reply 5 months ago

50v

0
AnilB26
AnilB26

6 months ago

Hello Broo pcb PDF sendmee