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I have designed a power supply with a 3kV output. I need connect it to external heat-sinked load. I have purchased some 15kV twisted pair cable to do this.

I am unsure the best way to bring this voltage from the board, to the load.

I have been told 600V terminal blocks will do the job.

Won't I be exceeding the voltage rating?

The voltage is floating from ground, also, so I will need two wires from the terminal block - one for VOLT+ and one for VOLT-. If using a terminal block, this means the full voltage will be imposed upon it (to my understanding.)

Is it better to just have a via, sized to the AWG of the 15kV wire, which is soldered directly into the board? Possibly then, coated with some high voltage insulation material such as silicon or what not to increase breakdown capability? Possibly I could use the PCB footprint of the terminal block, but not actually place the component at time of manufacture - instead just directly soldering the 15kV wires into the hole with HV potting applied over it.

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    \$\begingroup\$ 3 kV is in partial discharge territory. Can you use just one terminal block - space on the PCB - another terminal block? That way the PCB will do the voltage withstand. \$\endgroup\$
    – winny
    Feb 9, 2021 at 19:36
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    \$\begingroup\$ So a single input terminal block, and another separate terminal block with acceptable clearance and creepage away from it. This way, the individual voltage rating of the terminal blocks does not matter? For example, I could have a single input 600V terminal block and that would be ok? \$\endgroup\$
    – jvnlendm
    Feb 10, 2021 at 1:14
  • \$\begingroup\$ That’s how I would do it. Check the CTI of the PCB you are using and calculate the creepage requirements accordingly. This way, you’ll assume the plastic of the screw terminal provides no isolation and the entire terminal is at potential. \$\endgroup\$
    – winny
    Feb 10, 2021 at 8:23

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Won't I be exceeding the voltage rating?

Depends. What is the DC voltage rating of the blocks? 600VAC is about 850V peak so you are exceeding that.

I suggest using two single point (or two point if you can't get singles) terminal blocks if you don't like the creepage distance on the blocks (or exceeding the stated rating even if the spacing looks okay enough).

Consider having a slot milled through the PCB between the terminals to increase the creepage distance on the PCB, which will (typically) otherwise be limiting regardless of the design of terminal block.

Soldering directly to the board tends to cause a bunch of problems such as the wires breaking off near the solder joint after minimal handling.

If you do choose to solder directly to the board apply some form of strain relief (really bending relief).

3kV is low enough that you don't need to worry too much about corona, but it's good practice to avoid pointy bits that increase the field strength and can cause discharge. The resulting O3 tends to rot things as well as causing unnecessary loading on the HV power supply.

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  • \$\begingroup\$ Thank you very much for the answer and help! \$\endgroup\$
    – jvnlendm
    Feb 10, 2021 at 15:43

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