Eldarion and Bruce's build of Bob's Energy Converter

[eldarion]

I assume you meant to:
1. Close both switches
2. Open both switches
3. Close the negative-side switch?

er -- yea. I think. When I get it all working in the simulator I'll send you the spice model if you like. ... and then I'll be doing some testing to confirm that it works as designed ... and hopefully I'll stop blowing up drivers too.

mark.

Hi Mark,

I know what you mean about the drivers.  In the course of trying to drive the primaries with only the MOSFET driver outputs, snap crackle pop...all 12 SMT UCC27322s on my board are dead.

I really like the above idea, though, and will start working on a new high and low side driver board for the MOSFET totem pole you are describing.

Onwards...

Eldarion

[MarkSnoswell]

I know what you mean about the drivers.  In the course of trying to drive the primaries with only the MOSFET driver outputs, snap crackle pop...all 12 SMT UCC27322s on my board are dead.

ah -- gasp... the drivers have great speed and current buy lousy voltage ratings. Any back emf and they die.

Right now I am leaning towards these parts:

Drivers:
Intersil drivers http://www.intersil.com/products/pt/parametric_table_503.asp   *** fastest driver you can get and a reasonable price - $6.30 each. avail in 1x
EL7518  8ns rise and fall time into 1000pf, 12A peak current, 40MHz continuous operation.8 ld SOIC package only. Vcc 4-12 ,18V max.
http://www.intersil.com/cda/deviceinfo/0,0,EL7158,0.html

or IXYS ICDD414 - wich arent quite as fast but have high voltage rating and are reportedly very robust.


Output:
STGP6NC60HD  $1.17 ea
TO-220; Voltage, Vceo:600V; Voltage, Vce sat max:2.5V; Current, Ic continuous a max:6A; Current, Icm pulsed:21A; Power, Pd:20W; Rise time 5ns
http://www.st.com/stonline/products/literature/ds/13765.pdf

or

IRF820


Isolators:
NVE  Il711   150 mbps GMR isolator (2500V) --- *the* fastest you can get. Very new spintronic device. from NVE http://www.nve.com/index.php



You *need* separate power supplies for low side and high side drivers and the output stage. The low side driver and output still share a common line which needs filters on it. The high side driver is on a floating supply which gives it some inherent filtering.

[eldarion]

Hi Mark,

Ordered samples of the MOSFET drivers, 10 total!   I will try to obtain some IRF840s; I used to have some lying around, but alas, they were incorporated into other projects.

One thing is still bothering me: why does Bob's simpler driver board work at all if this kind of fancy switching circuit is required???  No matter what I do, I still cannot seem to get that type of driver circuit to work.  Maybe Bob can clear it up when I talk to him Saturday.

Eldarion

[Jdo300]

Hi Eldarion,

Just thought I would check in and see how things are going with your testing. I just did a quick skim over the last couple of pages of the post and I saw those waveforms that you were getting on the primaries. To put it bluntly, the look pretty crazy coming out of those IGBTs! From the looks of those output waveforms, it seems like your IGBTs are not switching fast enough to turn on and give you a sharp edge. Another problem could be that your power supply is not reacting fast enough to supply the current to the IGBTs. Are you using any filter caps on your V+ supply? If not, putting a few caps (47uF, 0.1uF, and 0.01uF for instance) in front of each of your IGBTs will help to clean up the waveforms very much. That may explain why the waveform looks fine when you only have one IGBT running.

Also, putting a large cap in front of your battery/power supply will give it more kick to help supply the current.

My other thought is about your magnetic bias. How smooth is the output waveform across the magnetic bias winding? I think you were using pulsed input to regulate the output voltage level? Also, how much current do you have flowing through the bias winding?

What were you doing when you blew up your UCC drivers? When I did some testing with them, I quickly noticed that it didn't take much to blow them up. But if you drive the primaries open-ended with the UCC drivers, you *shouldn't* have any problems.

Here's some more tips, the first thing you need to do is confirm that you have a rotating field. I would try placing a cup of salt water with pepper or something in it to see if the field has any effect on it. The rotating field that you need to have should be mainly electric in nature. From what I understand, the magnetic component is just a side effect of the changing electric potentials. Thats why I have been such a proponent of the open-ended drive. If you do it right, you will be able to generate an output on the longitudinal windings. I was able to do this with the green TPU that I posted videos about on YouTube (http://www.youtube.com/watch?v=X6NlO-fVr_U), though I was using much higher frequencies to get the effect.

Thats all I can think of for now, I want to get up to speed on what you are doing and maybe I can help you out more. Meanwhile, I'm still plugging away at my DDS controller, which thankfully is finally in the last phase of the design stage.

God Bless,
Jason O

[eldarion]

Hi Jason,

Thanks for the info.  I was driving the primary coils closed-ended with a very small pulse width when they blew.  Interestingly, on further examination, only the F1 (highest frequency) drivers blew--this is a good thing, as I can route around the dead chips for now and resume testing.

I had a large bank of capacitors at the power supply, but I will try putting individual capacitors on the IGBTs to see if that helps.  I had assumed that I was getting some weird waveform mixing in the core and failed to look for more obvious problems.

Eldarion