500W 12v to 220v Inverter

[doron1]

just how much  load would the circuit be able to withstand if i use my 0.24 Ohms which dissipates about 3Watts on the emitter side of the resistors because they are the only ones that i can find close enough to the 0.1 Ohms,10W resistors?
I am asking this because i don't necessarily have to produce 500W as yet,i just want to test the circuit with the resources that i have.

 

[audioguru2]

just how much

 

[doron1]

What type of loads/appliances/devices can be used with this inverter because i believe we can't use it on critical loads like  a computer or some other data capturing devices?

What is the purpose of the 0.1Ohm,10Watt resistor?Why can't we use a wire for short circuiting if that is what we want to achieve when the current is being drawn by  the load as 0.1 Ohm is really no resistance at all?

What is the purpose of the 4 2N3055NPN Transistors bacause I thought they were for current sharing because the 50Amps is too much for one transistor,eg,
50/4=12.5Amps.The transistors max rating is 15Amps so i thought they could handle this much current?

What type of power MOSFETS can i use in place of the transistors?

How do you connect the collector of the 2N3055NPN transistors when you have mounted them on the base of the heat sink?

How do you place the resistors  onto the heatsink?

I've found some 0.47 Ohms,5Watt resistors and I wanted to parallel them in 3s so i get an effective resistance of
(0.47*0.47)/(2*0.47)=0.235

(0.235*0.47)/(0.235+0.47)=0.157 Ohms dissipating about 15Watts
Do you think this will work in place of the 0.1 Ohm,10Watt resistors?

 

[audioguru2]

What type of loads/appliances/devices can be used with this inverter because i believe we can't use it on critical loads like

 

[doron1]

On the schematic given for the 500W inverter,ther are values given as 100R,1/4W is this suppossed to be 100 Ohms,1/4W or I can use any value for R as long as it has 1/4w dissipated?

The darlington paired transistors;are they to be used for amplifyng the signal out of the CD4047 chip or  for some other purpose?

If you can't mount the emitter resistors on the heatsink,where are you going to place them?I saw the pictures by COOPERMAN and he had mounted them on the side of the heatsink(see his pictures attached)

You said that the 3 paralled 0.47 Ohms,5W will have the project's voltage output reduced,by how much will the output voltage be reduced and what are the effects on the load connected?

 

[audioguru2]

On the schematic given for the 500W inverter,ther are values given as 100R,1/4W is this suppossed to be 100 Ohms,1/4W or I can use any value for R as long as it has 1/4w dissipated?

100 ohms, 1/4W resistors are very common. Use them.
You should never use a resistor at its rated power dissipation, it will be too hot. Its rated power is its absolute max allowed.

The darlington paired transistors;are they to be used for amplifyng the signal out of the CD4047 chip or

 

[doron1]

hie i was wondering if you could use 3A power diodes in place of the 2A  for back emf protection?

Does the 100R,1/4W resistor on the schematic mean 100 Ohms or you  can use any value of R as long as the ratio between the 100R,1/4W and 0.1R,10W is maintained?

Can i use a 60A Circuit breaker in  place of the 50A power switch or relay

 

[audioguru2]

hie i was wondering if you could use 3A power diodes in place of the 2A

 

[doron1]

i am having problems with my square wave generator.What is happening is that at the pins 10 and 11 of the CD4047 there is a constant voltage(I am using 5 Volts d.c to prevent heating of the chip) instead of the original square wave that i was getting initially when i connected the circuit.Then it was oscillating between 5v and 0v.

I have changed the chip 4 times and still there is no change so now i don't know what to do.I tested all the chips and they were fine,together with the LM358 Op Amp and everything is ok but NO SQUARE WAVE!!!! >

 

[audioguru2]

Hi Doron,
Something must be wired wrong for the CD4047 to get hot.
It is Cmos which has an extremely low operating current at such a low frequency and its opamp load draws nearly no current.
Didn't you make an oscillator like this one that is on the modified version?

View attachment 38957

 

[doron1]

I fixed the problem on the oscillator so evrything is working ok now.
I mounted the 4 2N3055 on one heatsink for each cycle,say when we have 1 cycle so i was curious as to how much heat they are  going to dissipate.you last said you need the specs for the heatsink so i was wondering what you were talking about
What exactly are you talking about when you say "Heat Specs" and can you give an example in relation to the 4 mounted transistors knowing their characteristics?

 

[audioguru2]

The "heat spec's" for a 2N3055 transistor are that it will be at its absolute max temp when it has a PERFECT heatsink that keeps its case at 25 degrees C. Then it can dissipate 115W.
A REAL heatsink also has "heat spec's" that are its thermal resistance. Insulators also insulate heat, so should not be used. 4 2N3055 output transistors plus the 2N3055 driver transistor plus the pre-driver transistor can be mounted on one heatsink per side without insulators, then insulate each heatsink from each other and from the chassis.

With a load of 500W on the inverter, the total heat is estimated at 100W. So each heatsink will dissipate 50W.

 

[doron1]

thanks audioguru for that piece of info. So are you saying that the 4 paralled transistors though each has a power dissipation of 115W alone when the are put together we get  only 50W dissipated,how come?

 

[audioguru2]

Hi Doron,
A 2N3055 transistor will reach its absolute max internal temp and can dissipate 115W only if it has a PERFECT heatsink that is impossible to have. The heatsink gets hot because it isn't isn't a PERFECT heat radiator. When the heatsink gets hot then you must reduce the power in the transistor. The transistor's case gets hotter because its mounting to the heatsink isn't PERFECT. The chip inside the transistor also gets hotter than its case because its mounting isn't PERFECT.

Another problem is that you will have 6 transistors on each heatsink making it hot.

 

[photoar]

Hello !

i'm trying to build the same project,
seems like i have the same problem - no wave output from cd4047 - just continuous juice....

checked all wiring, but it's fine
what can i do to solve it ?

 

[audioguru2]

i'm trying to build the same project,
seems like i have the same problem - no wave output from cd4047 - just continuous juice....

checked all wiring, but it's fine
what can i do to solve it ?

Did you make the WRONG circuit or my corrected one? My corrected circuit was recently replaced by the wrong one. I don't know why.

 

[photoar]

oh, now i see your attachment, and i guess it's the same as mine...

something is still wrong there...

i built this one....

 

[photoar]

do you have an idea how can i control the transistors with a 555 timer creating the wave ?

Thanks a lot !

 

[audioguru2]

My schematic is correct.
Check the pins numbers on your CD4047 carefully and if it doesn't work then replace it.

 

[MP1]

Photoar,
I got several complaints about the circuit you built. It is built like an audio amplifier and does not apply the same rules as all other square wave inverters. Other members have gotten better results by removing some of the power robbing and heat generating parts, making it more like the one which is now posted on our site.

However, if you are not getting a data stream from the CD4047, you have either pulled too much current through it or you have connected it wrong.

MP