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Old 2nd May 2005, 09:03 AM   #11
Electrons are yellow and more is better!
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...hey, hey, hey.... ......, Mr Glen Kleinschmidt had a dream and he wrote it down. The schematic has nothing to do with reality. I had correspondence with him when he was drawing this. All ideas were only in his mind and did never leave the computer. The 20 kW was short peak power at some minimal inspecified load. Those of you who can calculate know what load he was referring to.
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Old 2nd May 2005, 09:03 AM   #12
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Quote:
Originally posted by phase_accurate
I once found a web-page of a manufacturer making switching amps in the range of several tens of kW.
Those are mainly used for shaker tables or those large field coils like they are used on subs and minesweepers in order to compensate ships influence on the earth's magnetic field (to avoid detection or triggering of mines).
when I stumble upon it I will post the link here. Maybe they give a hint on topology as well.

Regards

Charles
I had some correspondence with the engineer from that company once. They build 1kW plug-in modules with current sharing control. No multiphase operation. They have installed systems up to a megawatt, for sonar.

Small wonder you get whales landing themselves on shores to die.
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Old 8th January 2006, 06:01 AM   #13
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Default Some clarifications from the designer!

A few clarifications from the designer!


G’day!

I was just browsing the web and I came across this by fluke.
I see that a few clarifications are in order, viz my amplifier design:

1) The design is class AB with class H supply rail switching. The supply rail switching significantly improves the efficiency and means that far fewer transistor pairs are required the output stage for a given power output.
I have drawn a diagram to demonstrate the principle here:
http://www.picknowl.com.au/homepages/glenk/railstep.jpg

2) Alme is entirely correct; the design is indeed rated at 5kW into 1 ohm. This was the design specification I based the transistor load line calculations on.
I specifically wrote a program in visual basic to plot the load lines with the class H rail switching.

Here is the load line for 5kW into 1 ohm reactive (45deg):
http://www.picknowl.com.au/homepages/glenk/loadline.jpg

The green line is the SOA curve for the parallel connected transistor pairs – as can be seen, there is plenty of reserve. This design is not a joke or a fantasy!

3) The reason for the 20kW title is that this design is part of a 20kW project, in which I intend to use 4 of these 5kW ‘modules’, bridge configuration, to make a stereo amplifier rated at 10kWrms per channel into 2 ohms.

4) This beast is not to be powered from a GPO, but from a 24V lead acid battery bank with switch mode power supplies providing the required rail voltages.

5) Yes! I do intend to finish building it, but I’m not giving any promises as to when it will be finished or when I’ll get the webpage once dedicated to the project up and running again – I have to finish renovating my house and fitting out my electronics workshop first.


I hope this clears a bit of confusion !

Cheers,
Glen Kleinschmidt.
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Old 8th January 2006, 06:58 AM   #14
Electrons are yellow and more is better!
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Hello Glen!

It has been a long time since I've heard anything from you. Your homepage which I had in my link list has been shut down since years. What about now?
http://www.picknowl.com.au/homepages/glenk seems not be there? Forgot the index.htm or maybe you haven't uploaded anything besides the pictures?

Just wondering: What are you going to use this amp for? 2 x 10 kW is pretty much to have at home.
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Old 8th January 2006, 08:54 AM   #15
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Hello P-A, I still remember you too!

Unfortunately, none of my amp stuff is currently on the web. I only uploaded those 2 pictures in my last post for this thread.

I can't believe that was 5 years ago already. I spent a small fortune on the output transistors, and they're just collecting dust in my shed.

As for what I'm going to do with the amp, I don't quite know the answer to that myself. I just wan't to built it, because I can, I guess.

Cheers.
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Old 10th January 2006, 08:49 AM   #16
Electrons are yellow and more is better!
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It would have been fun to see your monster come alive some day but meanwhile maybe you should build a Gainclone
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Old 15th January 2006, 09:06 AM   #17
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Now a 'Gainclone' would definately be a somewhat less ambitious project!
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Old 15th January 2006, 10:38 PM   #18
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Hi,
how did you calculate the SOA curve?
I did not recognize a slope change from second breakdown derating to a power hyperbolic curve.
For me it looks like a hyperbolic curve of max power dissipation, but moved to the right.
Upleft you have a current of 160 A and a Voltage of 33 V = 5280 W,
and at the right side at 160V a current of about 18A = 2880W.
How can this happen?
Onra
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Old 15th January 2006, 11:49 PM   #19
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Easy questions!


” how did you calculate the SOA curve?”


The SOA curve is taken directly from the graph on page 4 of the transistor data sheet:
www.onsemi.com/pub/Collateral/MJL21193-D.PDF


"Upleft you have a current of 160 A and a Voltage of 33 V = 5280 W,
and at the right side at 160V a current of about 18A = 2880W.
How can this happen?"



There are 25 transistors in parallel, so the current is multiplied by 25.


” I did not recognize a slope change from second breakdown derating to a power hyperbolic curve.”


You didn’t look closely enough!
The change in slope into secondary breakdown for these transistors is very slight – have a look at the graph on page four of the datasheet. Secondary breakdown starts at approx 80 volts. If you look closely at my graph, you’ll see a slight kink at approx 80V too – it is much less noticeable though due to the linear scale.

Cheers
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Old 6th November 2006, 10:28 PM   #20
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Just found Glen here

Glen, can you contact me?

Sorry for the use of the forum, but I think it's the only way to do it...

It's bacause of your 2001 design of the "3.6kW rms Audio Amplifier"

Regards,

Pedro
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