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Planning my first DRSSTC

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skawesome

Mon May 17 2010, 08:57AM

Registered Member #2861 Joined: Sun May 16 2010, 08:34PM
Location: Bavaria
Posts: 10

Hi
I'm planning a DRSSTC and have some questions to it. But first the specifications:

secoundary-coil
- diameter: 11 cm (4.3 in)
- wire-diameter: 0,3 mm
- height: 45 cm (17.7 in)
- torus: 11 cm * 45 cm (4.3 in * 17.7 in)
- number of windings: ~ 1500
- resonant frequency: 129.59 kHz

primary-coil
- diameter: 24 cm (9.4 in)
- space between windings: 1,2 cm (0.47 in)
- wire-diameter: 6 mm (0.24 in) (-> copper-tube)
- number of windings: 6

MMC
One string consists of 6 MKP-10-1600 330n; 4 therefrom parallel gives altogether 220nF / 9,6 kVDC.

halfbridge
consists of a FUJI 2MBI300U4H-120 (1200V, 800Apk).
power supply: ~650VDC (system voltage + voltage doubler)

electronics
- Steve Wards "New DRSSTC Driver"
- interrupter: this one (without Burst Mode)
- when the coil runs really good: CTC's musical interrupter

Now for the questions..
1. How much current does the driver need??
2. How big will be the power consumption approximately? Has anyone a DRSSTC with comparably specifications, so he could tell me how much power his coil needs?
3. In what way should I protect the grid against the DRSSTC (line filter, isolating transformer, fuses and so on)? Such things aren't really cheap if they have to transmit [insert answer of question 2 here] watt.
4. Is there anything you would not do like me? Please tell me.

so far..
greetings,
skawesome

PS: My brother plotted the coil with HiCAD. But there are not 1660 windings on the secoundary because the computer wasn't able to handle with it.

Edit:
Changed the secoundary-coil specifications.

Steve Conner

Mon May 17 2010, 09:47AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Power consumption is under your control, it depends on how you set the burst length and repetition rate of the interrupter.

For a coil this size, I'd plan for a couple of kilowatts.

As for line current: That depends on the power. Budget for a power factor of about 0.6, so the line current will be (power/voltage)*(1/0.6)

Your power output will probably be limited by how much current you can get out of the standard wall outlet in your country. (10A? 16A?) If you live in one of these countries that also has 400V three phase service, you might want to consider using that.

Protection: At least use a fuse or circuit breaker. Some basic RF filtering is also nice, this can be as simple as a capacitor from DC bus negative to ground.

TheBoozer

Mon May 17 2010, 09:45PM

Registered Member #1535 Joined: Wed Jun 11 2008, 11:37PM
Location: Northeastern Pennsylvania - USA
Posts: 117

I've been breaking open a few bricks of the Fuji series. One for example is a 2MBI300S-120

It appears to have a current limiting circuit in there similar to the Powerex RTC circuit in some of their bricks.

There's no mention of this in the Fuji datasheet. Powerex datasheets do mention it when they have it. I have no clue if this applies to your Fuji series bricks, but I thought it might be worthy to note...

Rich

Arcstarter

Mon May 17 2010, 11:17PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

TheBoozer wrote ...

I've been breaking open a few bricks of the Fuji series. One for example is a 2MBI300S-120

It appears to have a current limiting circuit in there similar to the Powerex RTC circuit in some of their bricks.

There's no mention of this in the Fuji datasheet. Powerex datasheets do mention it when they have it. I have no clue if this applies to your Fuji series bricks, but I thought it might be worthy to note...

Rich

I cracked open one of those Fuji 1.2kv 150amp (200 amps in the datasheet) bricks. I am now curious, what does this circuit look like, for fuuture reference? I'd imagine it involves a shunt resistor and some circuitry that disables the igbt by grounding the gate?

TheBoozer

Tue May 18 2010, 09:00AM

Registered Member #1535 Joined: Wed Jun 11 2008, 11:37PM
Location: Northeastern Pennsylvania - USA
Posts: 117

It looks like one little additional circuit with three leads. One lead attaches to the gate and two leads go to different spots on the IGBT. The two leads form a current mirror. Just like a shunt. I'm told people have had success snipping the two shunt leads on CM300 series Powerex modules.

Here's a photo I took a recently. It was only for size comparison. I could get a better closeup if requested. You can see in the very upper left, under the letter M of 2MBI the little die with two leads going to the IGBT below it.

Rich

skawesome

Mon May 31 2010, 04:54PM

Registered Member #2861 Joined: Sun May 16 2010, 08:34PM
Location: Bavaria
Posts: 10

News:
My brother and I made the primary attachment and the torus.

(sry, I have made no photo of the torus yet)

At first I wanted to use a variac to control the voltage of the DRSSTC. But variacs that are able to transmit the power i want, are quite expensive. So a friend of mine suggested to use a dimmer. I think i need a trailing edge dimmer, because of the capacitive load of the voltage doubler. Could this work?

skawesome

Goodchild

Tue Jun 01 2010, 02:34AM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

skawesome wrote ...

At first I wanted to use a variac to control the voltage of the DRSSTC. But variacs that are able to transmit the power i want, are quite expensive. So a friend of mine suggested to use a dimmer. I think i need a trailing edge dimmer, because of the capacitive load of the voltage doubler. Could this work?

skawesome

Sorry but you can't use a SCR like circuit with a doubler, you need to input AC to the doubler in order for it to double the voltage.

Herr Zapp

Tue Jun 01 2010, 03:11AM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

skawesome -

What type of conductor are you planning to use for your primary coil, what is its outside diameter, and what is the diameter of the holes in your primary support?

You may find that threading the primary conductor through 35 holes simultaneously can be a real challenge; that's why almost everyone uses "notches" that allow the conductor to be "snapped in" radially, vs threaded through all the holes.

Regards,
Herr zapp

Steve Conner

Tue Jun 01 2010, 10:38AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Goodchild wrote ...

Sorry but you can't use a SCR like circuit with a doubler, you need to input AC to the doubler in order for it to double the voltage.

Yeah you can! Just replace the two diodes in the doubler with SCRs. It worked for me.

Or you can use diodes in the doubler and insert a triac in series with the AC input, it amounts to the same thing.

I've built two SSTCs with the DC bus voltage controlled by SCRs in this way.

Cheap lamp dimmers won't work, because the rectifier load is so non-linear. A professional dimmer rated for reactive loads might work, but I built my own phase angle controllers with hard firing.

skawesome

Tue Jun 01 2010, 12:54PM

Registered Member #2861 Joined: Sun May 16 2010, 08:34PM
Location: Bavaria
Posts: 10

Herr Zapp wrote ...

skawesome -

What type of conductor are you planning to use for your primary coil, what is its outside diameter, and what is the diameter of the holes in your primary support?

You may find that threading the primary conductor through 35 holes simultaneously can be a real challenge; that's why almost everyone uses "notches" that allow the conductor to be "snapped in" radially, vs threaded through all the holes.

Regards,
Herr zapp

I'm planning to use a 6mm copper tube. The diameter is 24cm and the holes are made with a 6,1mm drill. I know, it will be not easy to get the tube into the attachment. My plan is to bend the tube to a coil and then "screw" it into the attachment. Maybe i will need some greace and a lot of patience. ;)

@Steve McConnor:
Okay. It's good to know, that someone allready did something like this. :)
I found found an IC (TCA 785) that could make this thing much easier for me. My idea was to rectify the 230VAC and use a MOSFET, because I can use SCRs only for leading-edge dimming. I will post a schematic diagram soon.

edit:
here is the very simple dimmer schematic. just that you dont get the "rectify-thing" wrong.

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