Connect a PCB with a cable with a High Voltage connector - Page 1
Forum section: electronics / projects

author: Javier
author_rank: Contributor
timestamp: January 01, 2015, 09:46:01 pm
content: Hello everybody,I need to connect 2kV DC link voltage to a PCB. Since the terminal blocks of the usual providers like Phoenix only go upto 1kV I thought of using a HV-BNC connector, namely a MHV. Now I’m searching in vain since hours for a way to connect a cable with a MHV connector to a PCB.In other words: I’m searching for a connector like this one:http://www.mouser.de/ProductDetail/Amphenol-RF/908-24100/?qs=sGAEpiMZZMuLQf%252bEuFsOrh35k6jkGdFnb2yZY6BNd8U%3dbut for MHV. The PCB that I’m making has so far only SMD components, so for me an SMD solution would be the best, but at this point I would take a THD component as well.Does somebody know of such a component or does somebody has a better idea how I can do that?Thanks in advance and happy new yearCheers!

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: January 01, 2015, 10:01:00 pm
content: Like DC? How about the stuff they use for LCD backlights?

author: SeanB
author_rank: Super Contributor
timestamp: January 02, 2015, 06:54:26 am
content: Use a 1kV rated block and only use the one contact, then use another spaced more than the minimum creepage distance away for ground. On the board you will probably be using a series of high value high voltage resistors in any case as a voltage divider, so you will in any case need to have the large open board area.

author: Javier
author_rank: Contributor
timestamp: January 04, 2015, 10:58:49 am
content: Quote from: Alex Eisenhut on January 01, 2015, 10:01:00 pmYes, it's a DC voltage. What stuff for LCD backlights do you mean exactly?

author: Javier
author_rank: Contributor
timestamp: January 04, 2015, 11:00:01 am
content: Quote from: SeanB on January 02, 2015, 06:54:26 amIn that case I could take just any one-pole contact and with enough creepage distance I could achieve the 2kV isolation. Or am I missing something?

author: penfold
author_rank: Frequent Contributor
timestamp: January 04, 2015, 02:16:23 pm
content: You can use a connector such as a molex or JST with some pins removed to give you the required clearance. This is quite an acceptable solution and is used in a lot of commercial equipment, it not necessarily 'safe' but not much is at PCB level. If you require better HF performance you really have to resort to directly soldering coax to the PCB with the required clearance from braid to center.

author: SeanB
author_rank: Super Contributor
timestamp: January 04, 2015, 02:25:27 pm
content: Quote from: Javier on January 04, 2015, 11:00:01 amYes, that is the simplest solution. Extra creepage distance and physical separation provides isolation to any voltage.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 04, 2015, 03:03:28 pm
content: What do you mean by "link"...? Just how hot is this DC..?!I would be OK with terminal blocks, leaving more than a few adjacent positions unconnected, or unloaded if possible. 2kV I don't think is a corona hazard, at least outside of contaminating conditions. Don't just add up the connector voltage rating, but give it a good margin beyond that (in addition to the margin that is surely already incorporated into their rating), that way even if several positions electrically break down, there's still more to go. (Same reasoning as using multiple resistors in series for sensing or dropping high voltages, etc. Redundancy.)Note that the connector block itself is probably rated for an isolation voltage, for safety purposes, period. That is, the voltage on any position, to ground, not just between neighboring positions. It would not be appropriate to wire distant positions in the same block, or even separate blocks, if the connectors themselves are liable to break down this way. But -- this will be a safety issue, so if the connections are made, well inside the equipment, with shields and the enclosure screwed in place, there will be no possibility for fingers touching, and I would expect something like a UL rating would be possible then.You could also use something absolutely dumb, like 1/4" QC connectors (especially if you need the current rating), again, as long as there's some way to insulate, shield, enclose, protect and safety-ify all that from curious fingers and ambient dust.Those long HV connectors are great for when you need that kind of safety, especially with some dielectric goop (silicone gel?) sealing them. Well, now we're talking more like 20kV or 200kV here... but if you need to go to lengths, you might as well go all the way right?Of course, mind that they're rated for the current, too.Example: my Trinitron monitor has a 1kV connection inside it,http://seventransistorlabs.com/Monitor/Images/Defl2.jpgit's routed on the board with adequate clearance, solid soldermask AND silk screen (I don't know if silk is considered to have any dielectric value on the PCB, but it certainly stands out, if nothing else), board routes when otherwise too close to other things (note the slot near the connector pictured, among others), and, as this is a single low current connection, it only needs a single pin connector, but presumably comparable voltages are seen on the horizontal deflection yoke connector (nearby), which has two empty positions between the pairs of terminals, on a 0.156" pitch connector.The rest is here if you're curious,http://seventransistorlabs.com/Monitor/index.htmlthe red wire connects from the deflection board to the CRT/neck board.Tim

author: Javier
author_rank: Contributor
timestamp: January 06, 2015, 07:46:13 pm
content: Hello Tim, thanks for your detailed answer. "DC link" is according to the IEV the translation of "Zwischenkreis", that is, the DC intermediate part in a power electronics converter.I took a look at your website, it's really interesting, hopefully you upload the details of the "Motor Controller" soon.CheersQuote from: T3sl4co1l on January 04, 2015, 03:03:28 pm