resistors for high voltage circuits - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: November 12, 2024, 03:47:17 am
content: I wanted to get some values of resistors rated for high voltage. I am wondering what type should I use.I see that voltage seems proportional to power, and for most types it looks like the starting point for interesting circuits might be 0.5 to 1 watt resistors (10kV maximum)The ones that are not like weird to me all seem to be the metal film type. Metal oxide high voltage resistors seem to be not available, at least I can't find enough of them to make a high voltage resistor kit.I thought they might be 'nice' enough that it would be possible to experiment on higher frequency circuits (i.e. I have a current mirror working, I see there is alot of research into making current mirrors have better frequency performance), so I thought focusing on non-wire wound types would be a good idea.Generally I am just more likely to do something if I have a 'e-series' of parts available.I thought maybe to focus on 'R68' series resistors from yaego. I wanted it like orderly, similar shape/size, etc.. .not a mismatch of axial, radial, foot longs, etcThis one is hard, I feel indigestion coming on quick ... maybe 2 hours of browsing and I want a alkaseltzer

author: Kim Christensen
author_rank: Super Contributor
timestamp: November 12, 2024, 04:19:28 am
content: I simply went on Digikey and filtered for high voltage resistors:https://www.seielect.com/catalog/sei-hva.pdfTE Connectivity (TE)’s metal glaze resistors

author: jonpaul
author_rank: Super Contributor
timestamp: November 12, 2024, 04:27:50 am
content: Copper: RE V res...I designed and mfg HV equip for many decades...best RBleeders , eg 100m..10G...Victoreen, Vishay thick film HV (flat ceramic) 10 ..20%series current limit, non critical: eg 100...100k OhmsONLY Allen Bradley carbon comp hot molded GENUINE vintage (we have boxes!)Divider for HV reg: Victoreen, Caddock avail in dividers, 1% etc but special order.No experience with modern/Chinese HV resistors.....Have an absoultely fantastoic dayJon

author: coppercone2
author_rank: Super Contributor
timestamp: November 12, 2024, 04:47:35 am
content: Well I am interested in things like high voltage current mirrors and cascode switches and stuff. some of it is in AOE x chapters.https://www.eevblog.com/forum/projects/high-voltage-constant-(low)-current-load/?action=dlattach;attach=1991599;imageWhat kind do you recommend for those applications?It looks like they might need to be kind of precise. Carbon comp I thought is more for something that takes a beating like a snubber?Like to narrow it down, I mean active electronics, all of it should be around transistors.I guess what I maybe am thinking is that its not built to 'pulse' things. Like usually my interests are precision-ish. I know your background that you talk about is 'pulse' or just... less regulated stuff, like tesla coils, flash tubes, etc.. where a large part of design seems to be to just not break when its getting beat on.My interests are mundane

author: jonpaul
author_rank: Super Contributor
timestamp: November 12, 2024, 04:52:08 am
content: Copper carbon comp have arge % tol and high tempco. ONLY for bleeders, series arc protection.for precision use 1% large watts metal film, check the votage ratings.We used many in series to get the V rqd.What R, W, max V?j

author: coppercone2
author_rank: Super Contributor
timestamp: November 12, 2024, 04:53:33 am
content: I don't know the only supply I have is 1200V 10mA and it looks like the currents are never gonna be more then like 10-20mA but voltages... I think 10-30kV is not too unreasonable in the future. I base this at what lab source I can afford to house and buy. It looks like they usually stop being.. affordable some where around 30KV and a few miliamps for true lab voltage power supplies.For resistors, I have no clue what the simulator and books might ask for lol

author: coppercone2
author_rank: Super Contributor
timestamp: November 12, 2024, 04:55:26 am
content: example of the first hV circuit I built in years from the current mirror thread, tested at 1kV and 50uA (pending safe connections and workspace for more)https://imgur.com/a/59hZhJ8I never liked them since I fried a few fly backs when I had no idea what I am doing at all, it seemed more temperamental and difficult then basically anything else I tried, now I think if I work slowly and carefully I can get some projects goingI am liking the current mirror because the HP 6181A is a "control box" I can use for the circuit, and its precise and stable enough to allow for some interesting measurements of my prototypesAnd I was hoping to stay with lab power supplies, and avoid transformer projects, for HV things, so I can limit the scope of the designs. I know if I start trying to make custom supplies its gonna get too crazy too quick.Like maybe in the future, some project like a apex HV op amp, cascodes, etc .. series transistors (voltage ladder) seems like where this research would end up goingAnd maybe HV RF type stuff. E-field generator for EMC testing was always interesting, or weird piezos (though that is extremely difficult I think)

author: jonpaul
author_rank: Super Contributor
timestamp: November 12, 2024, 05:48:18 am
content: Copper been into HV since 1950s. as a kid, then hoppyest, then EE, now retired...Suggest thsat you see the old HV sites and get a few classic HV text books.Read and learn.....Greg LEYH:https://www.lod.org/Steve's HV:https://stevehv.4hv.org/TCBA Teslahttps://teslauniverse.com/build/tcba-newsletterENJOY!Jon

author: coppercone2
author_rank: Super Contributor
timestamp: November 12, 2024, 06:21:06 am
content: is there a carbon composition crisis in the industry for reliable stuff?

author: jonpaul
author_rank: Super Contributor
timestamp: November 12, 2024, 01:00:25 pm
content: Vintage Allen Bradley USA carbon Comp, have boxes of them.Ham fleas....Jon

author: coppercone2
author_rank: Super Contributor
timestamp: November 14, 2024, 12:24:27 am
content: I think i see why the caddock is so popular, I am guessing you can use them to make the 'resistor ladder' for the series transistor switch, if they make a power versionI guess I will see what series BJT's behave like and if they need those zener diodes, assuming I can find a power supply that is more interestingI am starting to see the connectors for the higher voltages look scary/ridiculoushttps://www.physical-instruments.fr/wp-content/uploads/Assemblage-connecteur-haute-tension-GES-HC7-HXC-60-1EA8-2.jpgI don't know if I like this

author: factory
author_rank: Super Contributor
timestamp: November 14, 2024, 09:36:22 pm
content: Quote from: coppercone2 on November 12, 2024, 06:21:06 amSeems ceramic composition are the replacement for the non-inductive carbon composition resistors, also for surge & pulse applications, voltage rating always depends on the physical size/length.https://www.mouser.co.uk/c/passive-components/resistors/ceramic-composition-resistors/David

author: TimFox
author_rank: Super Contributor
timestamp: November 14, 2024, 11:02:44 pm
content: When I needed good high-voltage resistors, I used Caddock.They make units with ratings up to 48 kV.https://www.caddock.com/online_catalog/high_voltage/high_voltage.htmlFor bleeders and other non-precision applications, we used helixed carbon resistors from RPC(?), but I'm not sure they are still around. They made long units up to about 100 kV, IIRC.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: November 15, 2024, 07:11:45 pm
content: Just look at datasheets. Every resistor series both has a maximum power rating and a maximum voltage rating. For low value resistors, the power will be the limiting factor, while for high value resistors the voltage rating will be the limiting factor.

author: TimFox
author_rank: Super Contributor
timestamp: November 15, 2024, 07:24:03 pm
content: For critical high-voltage resistor applications, see if the datasheet includes the VCR (voltage co-efficient of resistance), which can be substantial.

author: coppercone2
author_rank: Super Contributor
timestamp: November 15, 2024, 07:41:27 pm
content: the point was maybe to find series people like

author: Kim Christensen
author_rank: Super Contributor
timestamp: November 16, 2024, 04:34:22 pm
content: Quote from: TimFox on November 15, 2024, 07:24:03 pmThe StackPole datasheet I linked above specs a VCR of less than 20 ppm/VWould 20 ppm/V be considered substantial? Just curious.

author: TimFox
author_rank: Super Contributor
timestamp: November 16, 2024, 06:22:32 pm
content: Quote from: Kim Christensen on November 16, 2024, 04:34:22 pmIt depends on the application. At 1000 V, that's a shift of 2%.Before retiring, I needed 50 megohm resistors that would change by < 0.1% at 10 V: that's only 10 ppm/V, which is difficult (not impossible) to find in a 1206 SMT package, even harder for smaller than 0805.

author: coppercone2
author_rank: Super Contributor
timestamp: November 16, 2024, 07:40:35 pm
content: its like they are not rigid enough, this happens with soft tubing and high pressure, suddenly its diameter increased. or stretchy tanks

author: TimFox
author_rank: Super Contributor
timestamp: November 16, 2024, 07:59:24 pm
content: VCR results from a material property of the resistive material. The change in resistivity depends on the voltage gradient dV/dxalong the conductive path: with physically short resistor bodies, the voltage gradient increases and the VCR of the entire resistor increases (for a given total voltage across the resistor). Ohm's Law is only approximate, but quite useful for many "ohmic" materials in practical "resistors".

author: coppercone2
author_rank: Super Contributor
timestamp: November 16, 2024, 08:17:21 pm
content: I know there is a weakening of the material as it passes current, I wonder if its related, or it has more to do with electrons.. plowing? their way through things.Like maybe its like running through an obstacle coarse with wind in certain places (fields, something related to the atom) that if you have enough energy you just get through? Like at low voltage they are too weak to get through some 'obstacles' so the amount of area they can go through is limited, but when you increase the voltage , its kind of like widening a hallway? Like trying to get through a fruit stand at 5 miles per hour and driving into a fruit stand at 50 miles an hour.Or maybe its like squeezing through gaps? That the electron is kind of 'elastic' and if it has velocity it can slide through some 'detours' in a atomic structure that it normally would not go in because they are too tight? Kind of like throwing a V shape object through a hole, if its slow it gets stuck on the wide part of the V, but if its fast it bends a little bit and goes through the hole.

author: TimFox
author_rank: Super Contributor
timestamp: November 16, 2024, 08:59:59 pm
content: The current-voltage behavior of solid conductors is an interesting topic in solid-state physics.Left to their own devices, such as flowing through a vacuum between cathode and anode, electrons would not follow Ohm's Law.Various scattering phenomena in the solid contribute to linear and non-linear behavior, along with temperature co-efficient, etc.For this, one really should consult a textbook on solid state physics: Google gives nothing useful on the theory.However, here is an historically-interesting NASA paper from 1969, where the energy of particles in a DC particle accelerator is used to infer the resistance vs. voltage of the old-school Allen-Bradley 2 W carbon composition resistors in the voltage divider from the high-voltage supply. The authors worked to separate the self-heating and actual voltage dependence effects on the resistors.https://ntrs.nasa.gov/api/citations/19690005066/downloads/19690005066.pdf

author: coppercone2
author_rank: Super Contributor
timestamp: November 16, 2024, 09:40:26 pm
content: yeah thats what I was thinking it relates to the Zinc in the aciebo telescope and VCR and EP.I see they have 1000 resistors and a dynamitron but I just thought to try to precisely water cool a resistor to try to compensate for heating.But I did notice something, softer material typically conduct better, and since current makes materials softer, it seems like a reasonable relationship (maybe part of it)One think it makes me think of is a buffing wheel (polishing), when it spins it blows ALOT of air, so things are repelled from it. But obviously if you get in contact with the wheel, it grabs and can pull something in really hard. Maybe slow electrons get 'blown away' from those regions, while high voltage electrons get through that barrier and get 'conducted' better, or worse. Not sure if VCR is usually positive or negative. I figured it would be less resistance, but if its more, then thats counter intuitive. So if you throw ping pong balls of increasing velocity into a buffing wheel, the very slow ones may get repelled by the air, and the faster ones will hit the wheel and shoot off.Or more simply I guess, a fan. Light things are protected from a fan, heavy things get blown up by a fan.atom orbitals kind remind me of fans

author: TimFox
author_rank: Super Contributor
timestamp: November 16, 2024, 09:45:56 pm
content: If you want to maintain the temperature of a set of resistors constant, you are better off using insulating oil (not water), as done with laboratory standards.For example, you can measure the resistance accurately of a resistor at low voltage (and correspondingly low self-heating), varying the oil temperature with an external heater, to see the temperature co-efficient.Then, you can repeat the experiment raising the voltage, possibly taking data points at different oil temperatures.Use wire-wound resistors in the other three legs of a Wheatstone bridge.I used a Wheatstone bridge with General-Radio decade resistors to evaluate the voltage co-efficient of 1206 SMT 50 megohm resistors for 10 V application.

author: coppercone2
author_rank: Super Contributor
timestamp: November 16, 2024, 09:59:11 pm
content: Hmm I guess I forgot that its high voltage.Well, usually by water cooling I mean some cooling liquid (usually some kind of glycol) bought commercially, using just water is a good way to make it stinky, I never recommend using actual water... those fluid are a balance between total dangerous slippery hard to clean pain in the ass and short circuit mess.The cooling fluids evaporate into like... stickyness, while oil can make you slip and cut your head open if you miss a spot.But If you do it your way, in a beaker, its fine. I was thinking to use pumps and heat exchangers because I got all the fittings and some 'test leads' together for that kind of thing, and its actually conveniant, much like hooking up wires. I even got little heat sinks I can use to fluid cool a bread board part lol

author: jonpaul
author_rank: Super Contributor
timestamp: November 17, 2024, 09:58:06 pm
content: AMP and Alden made special reentry HV connectors from HD Polyethelene.See the 15..35 kV CRT u;tor connectors in scopes and 30..200 kV connectors for X-ray tubes.Jon