A small INVertor need Help on transformer problem

[knark]

i want to make a small invertor that converts 12 volt dc to 220 v ac at 50 hz i am facing problems some people are telling me that i should have a heat sink with my transformer if i want to run any appliance!!!!! also i am facing current problems that need enough current to run the transformer!!!!! need some help that should i have a heat sink and if i should than hoiw can i built it and what type of transformer should i get for it the circuit i am making is quite simple and based on the schematic on this following link

**broken link removed**

 

[KMoffett]

some people are telling me that i should have a heat sink with my transformer

I think they were saying to heat sink the transistors, not the transformer.

run any appliance!!!!!

Too broad a requirement! Night light to washing machine?

Ken

 

[knark]

yeah i m sorry transistor it is but how to heat sink them as they will get too hot...... and also the power rating of that circuit is 100 watt which i want to have as power rating .......... and i want to run some normal speakers not buffers or light a bulb or a fan thats it not more than that !!!!!

 

[stephen87]

The heat sink must be put with the 2 Darlington transistors (Tip41A and Tip42A), because with the transformer it does not make any sense.

Regarding the type of transformer is a step up transformer from 12v to 230V.

 

[knark]

yes sir i understand and the transformer type is as u mentioned but how am i gonna heat sink those transistors ?????
how is a heat sink connected to transistor !!!!

 

[stephen87]

1. Add some thermal grease with the transistor => https://www-ece.rice.edu/~jdw/figs/grease_dab.jpg
2. place the transistor with the heat sink => https://www-ece.rice.edu/~jdw/figs/heatsink2.jpg

(this can be attached too with a bolt and nut)

 

[knark]

the thing shown in 2nd picture is heat sink i guess and will i find one in the market .......... and it would be more intutive of u to just give me some explaination regarding how to connect this transistor with a heat sink in the circuit ............

 

[stephen87]

Yes an electronics shop you can find a heatsink. A heatsink normally comes with a hole on the middle top. On the other side, if you see the 2 transistors (TIPxxx) you have a hole too on the top. Now you have to connect the transistor with the heat sink via a bolt (passes trough both holes) and a nut to attach everything.

The heatsink will only be connected with the transistor only and not with the circuit!!

 

[knark]

okei thankyou sir !!!!!!! so the only external hardware which is not shown in the above link diagrame is the heat sink which i have to connect will that do the work for me and give me the result i want
............... is there any other thing necessary in the above circuit which is not mentioned a part from heat sink heat sink!!!!!!

 

[stephen87]

i thinks thats all mate, the only thing is to take care since you will now work with a 230v output!

 

[knark]

take care of my self !!!!!!!!! well i can manage that thankyou sir !!!!!!!

 

[KMoffett]

First, powered by 12VDC, a 100W inverter, even if it were a perfect 100% conversion, would require 8.3A. Those transistors are only rated at 6A absolute maximum. At saturation, the Vce will be ~2V. The transistors will have to dissipate (8.3A*2V)/2=8.3W. That little heat sink would do almost nothing.

Ken

 

[knark]

so what do you suggest about the heat sink and transistor

 

[blueroomelectronics]

That weedy circuit is a toy, not a practical inverter design.

 

[knark]

so can i have a design which is practical !!!!!!

 

[blueroomelectronics]

Cheaper to buy one than build one. There are dozens of post a year about DIY UPS from folks in countries with unreliable power. 100W inverters can be bought for about $40 from China.

 

[knark]

sir i dont need to build a ups for my house or soomething like that i need to demonstrate the circuit in a small presentation and need to drive a fan or two three bulbs from my circuit .............. i know that this design is not practical for domestic use......... i just want to build one for own understanding..... so is that okei with it .... i mean to my vision it seems that the circuit can be upto my ecpectations ....

 

[4pyros]

Knark; You can use your circuit to demonstrate just dont use 100 watts, use like 60 watts. The more power you try to get out of it the more heat it will generat. If the transistors get to hot to touch at 60 watts output than use less power for the output.

The heat sink is a mechanical mass to draw heat away from the transistors and dissipate it in the air. You may want to google "heatsink" to learn more. To much to cover hear but generally the bigger and more surface area the more heat it can dissipate to the air. A fan blowing over the heat sink can help to.

Andy

 

[audioguru]

The circuit you found is too simple so it doesn't work. It has too many voltage losses so its output voltage is much too low when it has a load.
Its output transistors do not have enough current gain for an inverter and the output is a square-wave, not a sine-wave.

 

[knark]

thank you very much 4pyros i think i had it figured out thanks alll