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Registered Member #2390
Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381
Its not that using the coil will blow up the igbts. If you use it, you just have to make sure all the pieces of the puzzle fit, if you get my meaning. When i fried those igbts my duty cycle was way to high! My over current was set to 300amps. The boozer is correct about the oc circuit. Took me a while and a few bucks to learn that part! Winding the secondary in the book is pretty easy. I did mine by hand and it only took a saturday. I will save you a small headache here!! When you make the secondary, there is a copper strip at the bottom to connect the rf ground to. Bend it to the shape of the coilform, then solder all your connections to it, finally, glue it to the form when it cools. I soldered mine and glued it when it was still a bit warm. Not good. Have a look at the minibrute construction thread. That will also save you some grief! (If your modulator is improperly set you can fry the igbts with the setup exactly like the book!)
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Dr. Resonance wrote ...
You can probably get away with this. Most DRSSTC coils use 1600 to 2800 turns. The main reason is to keep the res freq down to a value around 50-60 kHz maximum. Most IGBTs start having serious switching problems above 60 KHZ. I usually design for 40 to 50 KHZ max.
Another trick is to use a rather large dia. sec, like 6 to 12 inch dia. This also keeps res freq down, usually with around 2,000 turns or slightly less.
And don't overcouple the coils. Values above 0.18 are unneccessary and usually asking for racing spark trouble. 0.2 would be an absolute max for reliable operation.
You know that you don't have to have the Fo that low. The only time you need it that low if when you are working with larger IGBTs like the CM150,CM300,CM600,ect...
For smaller IGBTs (like the 30N60,40N60,60N60) it's comment to have an Fo up to 200KHz not that thats ideal but they do work. I have a DRSSTC running a full bridge of 60N60s at 96Khz.
Registered Member #2591
Joined: Fri Jan 01 2010, 11:58AM
Location: netherlands
Posts: 76
ok, so I have to change some c's and r's on the advanced modulater, so that I can't blew up my igbt's, I wan't to use this interruper only on the minibrute system.
does somebody know's the limit timings for those igbt's (fairchild hgt1n40n60a4d) they are cooled well, each igbt han an own cpu cooler (coolermaster hyper 212 plus)
I don't wan't to blew up these by turning a potentiometer to far.
Registered Member #2390
Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381
Cant answer that one! That would most likely involve doing some extensive testing. Also, that would involve sacrificing some igbts to get the answers to that question. The modulator settings i gave you in a previous post are what the book suggests for initial settings. You will eventually want to tweak it a bit to get the best light show! If this is your first drsstc, like it was mine, you very well might go through a pair or three of the igbts. Dont let that discourage you! The payoff in the end is well worth the sacrifice, thats why these things arent sitting on a shelf somewhere!
Registered Member #125
Joined: Fri Feb 10 2006, 01:52PM
Location: Aalborg, Denmark
Posts: 155
Dr. Resonance wrote ...
You can probably get away with this. Most DRSSTC coils use 1600 to 2800 turns. The main reason is to keep the res freq down to a value around 50-60 kHz maximum. Most IGBTs start having serious switching problems above 60 KHZ. I usually design for 40 to 50 KHZ max.
Yes but that was before Finn made the Predikter circuit... I use two SKM400 IGBTs on a coil that runs 80kHz with no problems at all! And I bet that this phase lead feedback is the way for DRSSTCs in the future, as you don't have to worry about delays in your circuit and diode recovery transients.
Steve Ward also use phase lead feedback these days...
Registered Member #2591
Joined: Fri Jan 01 2010, 11:58AM
Location: netherlands
Posts: 76
This is how I wound the coil, one makita to turn the tube and some calculations for the teethweels. the acual winding process took 1,5 hour but I only looked at it in nerverse that it goes right all the way...
the actual size is 507 mm long / 110mm diameter with 36awg and 3596 turns (yes they are counted by a pulsehead), so, the only question for now is, use this coil or not and why?
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
tritium wrote ...
ok, so I have to change some c's and r's on the advanced modulater, so that I can't blew up my igbt's, I wan't to use this interruper only on the minibrute system.
does somebody know's the limit timings for those igbt's (fairchild hgt1n40n60a4d) they are cooled well, each igbt han an own cpu cooler (coolermaster hyper 212 plus)
I don't wan't to blew up these by turning a potentiometer to far.
Ok, lots of misinformation here.
Firstly, the Adv. Mod, like any other interruptor, controls the pulsewidth, duty cycle, and pulse repetition rate of the DRSSTC. And like ALL DRSSTCs, there will be a nominal range of operation that a particular DRSSTC can operate within without damage. However, if you push duty cycle, PRF, pulsewidth in any DRSSTC system, you have the chance to overstress components.
Secondly, to damage the DRSSTC, many different conditions have to met to cause overstress. The DRSSTC will not simply be damaged by incorrectly setting a potentiometer. Its going to require a high setting on your input power variac, high PRF (which creates high duty and high power conditions) and high pulsewidth.
Thirdly, the proper way to operate a DRSSTC is to start with the input variac low, PRF low, and pulsewidth low. Just like you would warm up your car in the morning before running it, you start out at low power and work your way up. You DO NOT bang your DRSSTC directly up into the highest power mode of operation.
Finally, if you really want to, the Adv. Mod is fully customizable. It utilizes simple 555 timer circuits so you can set the operational limits to whatever you want.
Registered Member #2390
Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381
My sincere apologies if i gave some bad info there! Eastern is surely the person that can accurately answer all of your questions about the minibrute!! After all, he designed that wonderful piece of technology!! Maybe i was a tad unclear. When i fried my igbts, my duty cycle was way to high. I did not realize that so i kept pushing the voltage of my variac. Bad! Smoked the igbts. When everything is like it is should be, the transistor death should not take place. I stated you may kill a pair or three because i assumed you would be learning like i was. I apologize for that. There was very careful thought in the design of the minibrute, i searched for a very long time for a system that was reliable and "as kick ass" (thats a direct quote from myself) as the minibrute. But it does take some work and learning! You wont be disappointed!
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secondary coil inefficient or not?
