how to make the SCR inverter

B

Thread Starter

banozon

Joined May 19, 2008

4

May 19, 2008

• #1

Hi all, I am new to this forum, from Hanoi Vietnam

Could anyone explain how to make the SCR inverter from AC220V/50Hz to ~10KV/1-2KHz/>100W for Ozone generators

Many thanhks !

banozon@yahoo.com

 

thingmaker3

Joined May 16, 2005

5,083

May 19, 2008

• #2

First, you'll need to rectify and filter your 220Vac. Next, use your inverter to create the desired frequency - use this to drive a step-up transformer.

Be extremely careful when working with these very dangerous voltage levels!!! Don't do anything until you are certain of all the hazards and the appropriate safety measures!

 

B

Thread Starter

banozon

Joined May 19, 2008

4

May 20, 2008

• #3

thingmaker3 said:

First, you'll need to rectify and filter your 220Vac. Next, use your inverter to create the desired frequency - use this to drive a step-up transformer.

Be extremely careful when working with these very dangerous voltage levels!!! Don't do anything until you are certain of all the hazards and the appropriate safety measures!

Click to expand...

Thank's for your reply!

I'll act with caution, but I don't understand how it work in this circuits:

http://www.freeinfosociety.com/electronics/schemview.php?id=1599

 

B

Thread Starter

banozon

Joined May 19, 2008

4

May 21, 2008

• #4

Fresh Ozone are producing on the surface of the porcelain enamel cup
Cold Plasma generative at about 6KV 20 KHz 30W (photo)

 

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Papabravo

Joined Feb 24, 2006

22,083

May 21, 2008

• #5

I would start by assuming that there is an oscillator with an approximate frequency of 400 Hz.

Then I would ask how long it takes for a 12V source to charge the 6.8 uF capacitor through a 1K resistor to the gate voltage of SCR.

When the SCR turns on part of the primary winding is shorted.

AC current will flow around the loop consisting of the 10 uF, primary winding and SCR. As the current returns to 0 the SCR will shut off.

Those hints should get you going.

 

Wendy

Joined Mar 24, 2008

23,796

May 21, 2008

• #6

Where would the oscillation come from? Once the SCR starts conducting I don't see what would break the current flow, which is required to turn it off.

 

Papabravo

Joined Feb 24, 2006

22,083

May 21, 2008

• #7

Oops I overlooked the shorted supply when the SCR is on.

 

thingmaker3

Joined May 16, 2005

5,083

May 21, 2008

• #8

Simulation (for what simulation is worth) agrees with the "doesn't work" assessment. At the Free Information Society, you get what you pay for!

 

Papabravo

Joined Feb 24, 2006

22,083

May 21, 2008

• #9

At least the OP had the good sense to ask about what was confusing him. Considering the reputations of many internet circuit posters I guess we shouldn't be surprised that there is some pretty useless stuff out there.

The better question might be is there such a thing as a working inverter based on an SCR? Could you build a better one with other components?

 

thingmaker3

Joined May 16, 2005

5,083

May 21, 2008

• #10

The key would seem to be building an oscillator with an SCR. The only such animal I've found on the net (same schematic copied to more than one place) fails for the same reason as the one at the F.I. site.

How might we go about making an SCR oscillate?

 

Wendy

Joined Mar 24, 2008

23,796

May 22, 2008

• #11

Far as I can tell, you don't. I have seen SCR's used as transistor like switches in pulsating power supplies, but unless you have something to break the current...

MOSFETs work better IMO. I've seen simple invertors using transistors using astable oscillator configurations.

An SCR would work well in a flyback setup I would think, but having never done it I'm not sure.

 

C

Caveman

Joined Apr 15, 2008

471

May 22, 2008

• #12

I think it works, but you need the right transformer characteristics. The mutual inductance between the top and bottom halves of the primary is probably most important. The inductance of the bottom side of the primary and the capacitor will resonate so that at one point in the cycle the current through the bottom half will take all of the current from the top half, leaving none for the scr, and turning it off.