10KVA DRSSTC (Complete) / Projects / Forums

Forums

4hv.org :: Forums :: Projects

« Previous topic | Next topic »

10KVA DRSSTC (Complete)

previous 1 2 3 4 next last

Move Thread

LAN_403

Steve Ward

Thu Sept 23 2010, 05:42PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

About water cooled primaries:

My research (both computer models and real tests) showed that going from 5/8" conductor to 3/8" conductor would be no efficiency hit (says computer FEM analysis), but real testing says *water cooled* 3/8" is less AC resistance, so more efficient, though the difference is small. Anyway, that result depends on keeping the conductor cool, whereas the 5/8" was not actively cooled so ran hotter (and thus, more resistive). The RAC (at a given temp) is basically the same despite the large reduction in surface area, because its in fact the large surface area that tends to have an unwanted effect of more eddy currents due to the coil's own magnetic flux. This is the reason why ribbon is generally not as good as tubing, though sort of for different reasons (namely, you can crowd the turns too densely).

So, our latest systems designed for our tesla coil shows use 3/8" copper with water pumped via $10 fountain pump from harbor freight tool. My attempt at measuring the leakage current through the water hose via CT was suggesting something like 500mA with 9kV peak on the primary. The same measurement repeated *without* the tube going through the CT, also said 500mA... so even the pearson 411A suffers from CM rejection issues in the presence of the primary coil. Anyway, the leakage current through a few feet water with a 1/2" diameter hose is negligible. As a precaution, i used a shielded power cable to the pump, and let the ground braid make contact with the water in my bucket/reservoir. Using about 3-4 gallons of water keeps the primary cool for about 30-45 minutes of constant running. Since our show is usually not more than an hour long, and the coils dont run 100% of the time, this works out to be plenty adequate, so no real need for a heat exchanger.

Goodchild

Thu Sept 23 2010, 08:32PM

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

This is very interesting, so basically you are grounding the water to earth to prevent primary current from getting into the water bucket and into the pump and into the mains AC and such.

Just wondering Steve ware your test with regular tap water or distilled water? Because with my tests with water and high voltage, distilled water actually makes a good isolator for the most part.

None the less all good information to take into account.

Shrad

Thu Sept 23 2010, 09:22PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

just use distilled water if you don't want electrolysis to occur

you also want a big flow so if you can, make a closed loop circuit and use a chiller and fan from a car or a shop fridge (easy to grab)

they use water cooling in laser power supplies, involving CW 300V 30A, sometimes pulsed or different voltages, and these issues are overcome with distilled water or deionized water

just my piece of advice from my personal field ;)

Steve Ward

Fri Sept 24 2010, 06:17PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

I used tap water. Also have used well water and other stuff that I bet most people wouldnt want to use for water cooling electronics. Even if the leakage current was an amp, it'd hardly matter since the bridge duty cycle is so low. I wouldnt bother with distilled water since its gonna get a bunch of stuff in it anyway once you run it through the primary.

The grounding of the water bucket was mainly in case i got a streamer hit to it, rather than have it inject current into the primary or pump, it could get back to RF ground as needed.

Goodchild

Mon Dec 20 2010, 05:27AM

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

Over the past week Steve Caton and my self got a lot of work done on this coil and also a twin that Steve is building. Yes you heard it right twin 10KVA DRSSTC.

Over some free time that we had over winter break we constructed the toroids, primarys, bases, and also finished both secondarys. It didn't hit me till now how big of a coil this really was until the toroid was finished and got put up top.

Here are some photos of the build:

Bending the tube for the toroid
5271637516 96377b66f2

building the toroids
5271096719 657bcb0655

The primarys
5271142433 072c3fded0

and finally Steve and my self standing next to our coils
Steve and his coil are on the right and my coil and I on the left
5271627792 Fae9eb2147

More images can be found here:

Finn Hammer

Mon Dec 20 2010, 06:14AM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Great work you are doing. I saw your photos on flickr, nice to see someone posting scope shots, keep doing that here as well.
Looking forward to seeing your solution when it comes to driving those CM600 gates!

Cheers, Finn Hammer

Ruben

Mon Dec 20 2010, 12:14PM

Registered Member #3263 Joined: Sat Oct 02 2010, 04:43AM
Location: Sydney, Australia
Posts: 34

Really nice looking work so far.
I'm curious, what did you use to machine those toroid supports and secondary end caps?

Goodchild

Mon Dec 20 2010, 06:08PM

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

Great work you are doing. I saw your photos on flickr, nice to see someone posting scope shots, keep doing that here as well.
Looking forward to seeing your solution when it comes to driving those CM600 gates!

We plan to use some rather large gate drive transformers to drive the gates of the CM600s. We came to this solution because of it's simplicity compared to high side gate drive. Ive driven large bricks in the past (such as CM300s) with GDTs and with great success, so I figured why could it not be applied here?

Really nice looking work so far.
I'm curious, what did you use to machine those toroid supports and secondary end caps?

Yeah those end cap were a pain to make. I don't have access to a CNC or machine shop. We machined all of the parts for these coils using only hand tools, drill press, and a band saw.

RickR

Mon Dec 20 2010, 07:05PM

Registered Member #93 Joined: Thu Feb 09 2006, 04:11PM
Location: Houston, Texas
Posts: 64

Nice looking coil(s)!

I've got a question though. Are you planning to connect the separate rings that constitute your topload together electrically? Otherwise it would seem to me that they would constitute independent single turn secondaries. If you are going to tie them together, how do you plan to do it? I'm asking because I'm planning to construct similar toroids but was going to use a continuous piece of copper tube wound in step fashion to produce the toroid. That way, individual rings wouldn't have to be connected together. I just couldn't think of a way to connect the individual rings that looked decent and at the same time was easy to assemble.

Thanks,

Rick

Dr. Drone

Mon Dec 20 2010, 07:22PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

previous 1 2 3 4 next last

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob