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Proud Mary

Mon Jan 07 2013, 07:20PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Physics Junkie wrote ...

Notice that small rise inbetween pulses, Is this anything to be concerned about? I cant imagine why that would be a problem but just asking to make sure.

Perhaps it's caused by poor power supply regulation - when the load is reduced between pulses, the voltage rises. I doubt that it could make a measurable difference to circuit performance though.

Physics Junkie

Sat Jan 12 2013, 08:44AM

Registered Member #7267 Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407

Well, a lot has been done to try and improve a few things. I've made a eagle pcb for the controller and driver. I am going to try and etch a board for the first time

Im just waiting on the pos copper clad board and some wire size drill bits to ship next week. Also waiting on some items to try and put together a little rf detector. If the pcb etching is a success, I will probably end up making a full bridge board to make everything less sloppy. I've used darned veroboard for my recent controllers, dbl sided copper clad etched with dremel tool for full bridge and its just messy with wires, and there is probably something i am overlooking because of this.. so hopefully a nice pcb will help clear things up. I've meticulously gone over the board design and since eagle pcb shows you which pins are connected together according to the schematic, I have no idea where I can go wrong... I've practically got the whole schematic memorized now lol

Could somebody please explain how to properly phase the CT's for the current feeback and ocd? I didnt know if this was a problem or not until I read a thread recently that said CT's must be phased correctly, Ive searched around but I cant find out how exactly to do this with an oscilloscope and/or how to tell if the phasing is correct or not. Should the two CT's have identical phasing? any suggestions and methods for checking this would be very much appreciated....

lightlinked

Mon Jan 14 2013, 08:31PM

Registered Member #2087 Joined: Tue Apr 21 2009, 08:32AM
Location:
Posts: 115

for the CTs direction, the right hand rule from physics class. I don't remember anything like that so I usually just reverse the "polarity" connection since i have the CT connected to the driver board with pin headers/JST plugs, not so easy to do if you use BNC or something. I noticed on EVR's new flexibrute

there is a phase reversal switch for the CTs.
can we see some pics of your things so far?

Physics Junkie

Tue Jan 15 2013, 12:17AM

Registered Member #7267 Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407

lightlinked wrote ...

for the CTs direction, the right hand rule from physics class. I don't remember anything like that so I usually just reverse the "polarity" connection since i have the CT connected to the driver board with pin headers/JST plugs, not so easy to do if you use BNC or something. I noticed on EVR's new flexibrute

there is a phase reversal switch for the CTs.
can we see some pics of your things so far?

Yeah I figured to just switch the "polarity" connections, I'm using the typical molex connection, so popping out the little pins and swapping them is no big deal. I was wondering about the CT phasing just because I have no idea if this is actually a problem in my setup. And like you said, I suppose I could switch them to see if it makes a difference, but if there was a way to actually test if it is wrong in the first place.

Anyways here are some pics:
Sorry everything is in pieces, but as you know from reading this thread, I am doing a lot to make everything better in general. As you will see, a lot of the layout is pretty much exactly the same as Steve Wards DRSSTC1. Only difference is that I am using Dan McCauley's 2nd gen schematics from his Electrical and Mechanical Design book. I took more pictures then what I attached here. More are in the ATTACHMENTS forum, here

topload made from 90degree pvc elbows, sanded down many times, covered with filler, sanded again many times, sprayed with enamel many times, and then wrapped with aluminum tape and smoothed. It's actually a very nice toroid

Secondary, its okay, I could wrap a better one but right now its probably the last thing I'll do with this project.

Primary...

MMC. This could be made better, I know....

Top of the Full bridge, I just remade this last night, trust me you dont want to see what that last one looked like

Bottom of the full bridge, with plenty of caps and more where that came from

GDT's thanks to EVR

simulated waveforms look great!!!!

CT's

Controller of death

. Now you see why I am making a PCB for this

My gosh its a damn jungle in there! Honey I shrunk the kids in the tesla coil circuit...

just a quick pic of the PCB design, going to kinko's tmoro to get it put on transparencies. The pre-sensitized board should come tmoro along with the wire sized drill bits, and stuff for a rf detector. Unfortunately the developer wont come for another week or two

Other things that I am changing that are not in the pictures:
Instead of the 400V 10uF caps for the full bridge, I ordered some 2kV .1uF caps to try, but I think either would work regardless. Also some heavy duty high current cable for the primary connections. The cable I am using now is just low-medium grade stuff, I dont have access to machinery to make proper copper buss conections. If I remember anything that I left out, I will add later. Please Share your thoughts and comments on anything above! I am open to some constructive criticism and would very much appreciate any suggestions on things to be changed or make better. Thanks For all the comments and to everyone who has given their input and help so far!!

p.s. Did I mention that this is my first DRSSTC build? that is why everything (design and schematics, etc..) is copied from other people's builds, and also why it probably doesnt look very "high quality/very well made" as I said I dont have access to use cnc machines and other stuff like that to make a top notch looking build like many other quality systems you see elsewhere on this forum and out on the interweb, even if I did I probably would not have done that since it is my first DR.

Physics Junkie

Tue Jan 15 2013, 02:11AM

Registered Member #7267 Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407

Already forgot a pic

sorry for dbl post! dont know how to edit it in

IGBT's and heatsinks

Graham Armitage

Tue Jan 15 2013, 03:39PM

Registered Member #6038 Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248

I have had a great success etching my own boards using the laser printer and magazine paper by ironing the toner onto the copper - lots of web articles describing the process. Don't use photo printing paper as some suggest. Cheap glossy magazine paper is the best. Makes very clean and good looking boards. Also allows you to apply a silkscreen layer to the finished board. God luck.

Physics Junkie

Tue Jan 15 2013, 04:57PM

Registered Member #7267 Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407

Bushman wrote ...

I have had a great success etching my own boards using the laser printer and magazine paper by ironing the toner onto the copper - lots of web articles describing the process. Don't use photo printing paper as some suggest. Cheap glossy magazine paper is the best. Makes very clean and good looking boards. Also allows you to apply a silkscreen layer to the finished board. God luck.

I tried this with poor success. I believe due to the iron I used was either too hot or not hot enough. The toner kind of blobbed and smudged around. I got better success just letting the iron sit on the paper, rather then moving it back and forth. But it still did not apply all the toner for some reason. So I'm trying the "darkroom" style with photo sensitized board. When I make the board I will probably rake this topic to a different forum and discuss people's methods

Physics Junkie

Sun Jan 20 2013, 07:11PM

Registered Member #7267 Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407

I'm trying to troubleshoot the newly etched board. I'm having possibly the same problem I had before (which i'm still unsure of) and I've narrowed down to either poor power supply regulation, or a fault in my interrupter/signal generator. What is happening is that my 15V regulator wants to kill itself. Like before, I pump a 100khz square wave 10V peak to peak from my signal generator to the Primary current feedback circuit, and interrupter is set to 250us PW 100hz PRF. It seems that as long as I dont have my GDT connected, everything is all fine and dandy. But as soon as it's connected, the 15v regulator heats up instantly and the 15V LED dims. This is making it difficult to take any sort of measurements such as correcting phase and differential G-E measurements of IGBT's on the bridge. So going back to troubleshooting the controller.. I've ripped out all the IC's and checked for shorts and blown components, but nothing. everything is new.. I've checked for shorts on the circuit board, nothing there either, I made sure of this before I started soldering. The GDT is wound just fine, kind of hard to mess up pairing a bunch of white wires

. Whatever problem I am having now must be the same problem I was having before, everything has been re-done and made with fresh components, new bridge, new controller, new GDT's.. only thing not new is the Interrupter... ever experienced funky things like this with high pulse width on the interrupter? BTW its steve's interrupter with burst mode.

Signal

No GDT connected

Now the GDT is connected, 15V regulator starts dieing.

Bridge

15V

I decided to monitor the regulator when I applied power to the circuit whilst having connected the GDT, just to make sure that the regulator is not shorting out and dumping 18+V into my IC's. As you can see it's not shorting, Just getting extremely hot. But all the IC's including the UCC gate driver's stay completely cool.

So, any ideas?

Ash Small

Sun Jan 20 2013, 07:58PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Physics Junkie wrote ...

Already forgot a pic

sorry for dbl post! dont know how to edit it in

If you scroll down below 'General Chatting' and 'Sale and Trade' sections, you eventually get to 'Attachments'. In there is a thread titled 'Pictures For Use In Threads'. Post pics, etc in there, then use the 'Edit' button in top right hand corner of the post, and use 'copy' and 'paste' to place the pic where you want in your original post.

It's a bit long winded, but it works.

Graham Armitage

Mon Jan 21 2013, 12:46PM

Registered Member #6038 Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248

When I first built the driver circuit I had a similar problem. Everything would run fine, and then after a short while the 15v regulator would overheat and the voltage drop. Discovered a 10uF cap next to the regulator was installed backwards and would slowly leak causing a short. Not saying this is your problem, but caused me a lot of pain trying to find it. I did not have the GDT connected when experiencing this.

Similar to the problem I am having now, it's confusing why the GDT would have this impact. What happens if the GDT primary is connected but the secondaries are left open? Does it still overheat?

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