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New DRSSTC CM300 Build

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Dr. Brownout

Fri Oct 12 2012, 03:53AM

Registered Member #2405 Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140

I thought I would post some pictures of a new build. Built around a full H-Bridge of CM300 bricks. Signals all look good. Almost ready to fire it up, I did fire it up without the secondary to check the primary current wave form and it ran good.

Specs are:
Secondary
9" secondary diameter
48" winding length
25 gauge magnet wire
6" x 24" spun aluminum toroid
Fro 54Khz

Primary

2" copper ribbon
Tapped at 10 Turns
Primary tank cap is .225uF

Driver Circuit
Driver is based off of Steve Wards 1.3B the MOSFETS are different than what he used and the burden resistor on the OCD CT load is different I am using a smaller burden resistor dropped it to 5 ohms. The GDT is comprised of two ferrite cores with 15 turns 1:1:1

H-Bridge
Two CM300DU-12NFH configured into full H-Bridge
120 Volt input into a doubler
Bus caps are two 2000uF 450V 525V surge
Snubber caps are two 4.7uF in parallel across the HVDC bus
340 VDC bus voltage.

I am going to add some LED lighting and light the cabinet up in blue with one 1 watt LED...wanted red and blue but I looks like I am out of red side emitting LEDS I tried white in there with blue but to me it was kind of lame so for now only blue.

Initial testing shows all looks good. I will post some pics of the wave forms. If it dont rain this weekend I will see how well it performs and get some spark pics.

Kizmo

Fri Oct 12 2012, 05:44AM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Nice to see another brick coil coming together! Have you scoped your inverter output voltage? Your bridge bus layout looks like it has a bit if inductance

Dr. Brownout

Fri Oct 12 2012, 11:01AM

Registered Member #2405 Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140

Kizmo wrote ...

Nice to see another brick coil coming together! Have you scoped your inverter output voltage? Your bridge bus layout looks like it has a bit if inductance

Hi Kizmo,
I did scope the output and did not see any ringing, I will be changing( at some point) that bus work over to all copper but for now I used what I had on hand, I will post pics of the current wave form and the bridge output later today.

My concern is really the bolts holding the bus work together, I will need to pay close attention to the thermal expansion of the bus bars I would not want them to loosen up.

That heat sink takes up a lot of real estate but again its all I had as a matter of fact I have three more just like it. I wanted the bricks to be side by side but they would not fit that way in this heat sink so I had to go end for end.

Dr. Brownout

Sat Oct 20 2012, 01:43AM

Registered Member #2405 Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140

Kizmo wrote ...

Nice to see another brick coil coming together! Have you scoped your inverter output voltage? Your bridge bus layout looks like it has a bit if inductance

I finally got around to getting some scope shots of the gate drive and primary current.
The primary current was tested with no secondary in place. The GDT I used fir this is a couple of 78 material toroids stacked with 16 turns on each winding ratio is 1:1:1 measured inductance is 1.416mH its a little low for 54Khz but it does not seem to load anything down.

Dr. Brownout

Sat Oct 20 2012, 01:56AM

Registered Member #2405 Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140

Here is the gate drive signal. I need to get a scope shot of the H-bridge output. I did scope it but forgot to take an picture of it. However it looks pretty clean.

Josh Campbell

Sat Oct 20 2012, 03:20AM

Registered Member #5258 Joined: Sun Jun 10 2012, 10:15PM
Location: Missouri - USA
Posts: 119

Interested to see your final results on this. I wanted to throw a brick DRSSTC together for Halloween using my IH setup to drive it if I have time. Is the heat sink the only thing keeping you from laying your IGBT's out with the bus configured properly? I guess if the signals look ok though it's all good as long as the bus does not heat up like you said.

Ultra-low inductance 2MBI300L-060 setup running on 220:

If your switching your IGBT's in ZCS mode they don't put out much heat anyway. You could probably get by with a small bit of overhang turning them sideways. But if it works as is no point in messing with it, it looks really nice already.

Dr. Brownout

Sat Oct 20 2012, 03:33AM

Registered Member #2405 Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140

Hi 2bytes,
Yes that's the exact reason the bus work is like it is. The heat sinks are just so big and the flat area of the heat sink is so narrow and fairly deep. So I had to lay the bricks end to end I wanted to to lay them side by side but there was just no way on these heat sinks. I have 3 more heat sinks just like it. It looks to me like it was a very large heat sink and then cut into sections. They were found at a flea market already chopped up in sections. I was not sure what I was going to do with them but then decided to use one of them for this project.

Hopefully if the weather is decent this weekend I will see if I can get some spark pictures.

It did not turn out to bad for what I had to work with I was afraid I was not going to get everything to fit in that little cabinet but it did. Now I just need to make a Midi interface for it.

Dr. Brownout

Sat Oct 20 2012, 05:07PM

Registered Member #2405 Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140

I took a scope shot of the output from the H-Bridge under no lead, there is some ringing but its not bad just a few cycles I expected more. I could probably add more snubber capacitance and clean it up even more I am using two 4700uF caps across each rail, but here is the interesting thing, if you look at the two photos each shows the same amount of ringing and again within acceptable limits...but look close at the wave forms ( sorry about the focus my scope sometimes hates differential measurements). One wave form is not symmetrical while the other is.

I noticed this after I took the first photo and looked at it on a bigger screen, the on time is quite a bit longer than the off time. But now in the second photo they are symmetrical. I was using a function generator to apply a sine wave feedback at the Fro of the coil which is 54Khz. I switched the leads around and the wave form became symmetrical like it should be.

In the real world this could not happen because if the feedback transformer leads are backwards the coil just wont run and hence no output. So if anyone else runs into this issue during testing this seems to be the cause.

1350752830 2405 FT145337 Cm300 Output Wave Form

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