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| Open HV Probe 40kV |
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| beanflying:
:'( So many needless ones and that is just the tip of the list. Lichtenberg wood burning is just asking to die unless you are very knowledgeable and well set up. For those that haven't seen it done High Salt content water and HV :scared: OT but on the grounds it is my Topic. NST Jacobs ladder Saddle (will suit any 4" wide units) and slide adjustment for the electrodes. 50+mm minimum Vertical separation to any metal parts. Two small inverted heatsinks to make sure any heat is kept from the PLA mounted on two pairs of sliding mounts. Could easily be mounted on a board away from the NST too. About 1/2 way into the main saddle on the little Ender Pro. The Corona Probe version is ready for a test too but I am tied up for the day but will get to it later maybe. Edit Added photo. Starting to get the bits arranged for the inner of the voltage divider probe. Ohmite Resistors as discussed earlier and Tinned Copper sleeve. |
| beanflying:
24 Hours of print time later the NST Jacobs Ladder Saddle is finished, tested and works as planned. I did try attaching on the front fin to Earth but didn't get any current reading which is to be expected as it has more isolation due to the ceramic insulator at the tip and increased distance. The slides on the saddle allow for shorted to 20mm+ of gap which won't jump without the probe. Nothing new learned in particular just a few more safer/nicer bits than I used to have added to the kit. I will be stripping the probe shown down for the same epoxy coating treatment as the divider one. The NST Saddle will likely get the same treatment and time to repaint the NST outer shell. ** All Test Gear in the shack was unplugged during this playing. https://youtu.be/Qx7eH9snu3U |
| Helix70:
I work on MV switchgear products for the outdoor market. We rapid prototyped a housing using fdm printing using abs. It's dielectric withstand was terrible. It isn't the abs that's the issue, its the partial discharge due to the air trapped in the print. I certainly would not hand hold a probe that was printed to the same dimensions as a proper vacuum molded silicon HV probe ( MV actually), I wouldn't trust it. My two cents. |
| beanflying:
--- Quote from: Helix70 on April 28, 2019, 09:41:27 am ---I work on MV switchgear products for the outdoor market. We rapid prototyped a housing using fdm printing using abs. It's dielectric withstand was terrible. It isn't the abs that's the issue, its the partial discharge due to the air trapped in the print. I certainly would not hand hold a probe that was printed to the same dimensions as a proper vacuum molded silicon HV probe ( MV actually), I wouldn't trust it. My two cents. --- End quote --- Do you have any figures on that? Were you using a Hipot tester or what for your testing would be interesting? Thanks :) Sort of relevant too if you believe it was air causing the issue was your enclosure printed with walls thick enough to allow infill? As shown a page back the barrel tips have virtually zero infill until well back from the tip other than any under extraction (poor setup) that may occur. |
| Helix70:
We have a 110kv capable transformer/capacitor in a chamber that we use for power frequency and partial discharge. We also tested at our lab in Germany for BIL of 170kv. Basically our magic number is 50kv for power frequency testing, and the partial discharge was really bad. Due to the size, our infill was not 100%, so yes that is not good, but even 100% infill will lead to bad partial discharge performance. That's why everyone in the industry uses silicon. HV stresses are just not good. We ended up flashing over and blowing a hole in the side of the printed housing at about 75kv, but that's another story. |
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