High Voltage Power Supply safety, grounding and discharge

Thread Starter

TechnoDesign

Joined Apr 1, 2021
5
Hi there,

I'm making an experimental setup that I need to connect 7Kv to a 3D printer nozzle and the printer bed.

The power supply that I have doesn't have a ground pin for AC. Just two wires are coming out of input which I soldered it to an AC plug (120v/60Hz)

Here's the link to the power supply:
https://www.aliexpress.com/item/322...VdgWiAx3Gyw81EAQYASABEgIzofD_BwE&gclsrc=aw.ds

My questions are:
1-As shown in the picture in Aliexpress link above, the input wires are thin. Is it safe to use those for AC? Assuming I have done proper soldering and insolation with heat shrink.

2-As the High Voltage Power Supply doesn't have a ground, wouldn't it be hazardous?

3-When I turn off the Power Supply, do I need to wait for it to discharge?

4- Do I need to connect the output ends by a large resistor to prevent arcing?



IMG_20210331_212815.jpg

Screen Shot 2021-03-31 at 9.33.53 PM.png
 

Attachments

MaxHeadRoom

Joined Jul 18, 2013
23,596
Appears to be typical Chinese methods for wiring etc.
There won't be much to gain by earth grounding one side, although it many HV tables such as plasma etc, usually do.
 

DickCappels

Joined Aug 21, 2008
7,689
I would earth all metal parts that are not already earthed or otherwise referenced to earth (I am thinking about the ungrounded output of your power supply. , even those "floating" on plastic that can get near the high voltage conductors.

My high voltage experience is mainly 15 kV and up so I might be more cautious (read that as "scared of a shock") than some.
 

ApacheKid

Joined Jan 12, 2015
418
The details on the site suggest the device is isolated from the mains supply, there seems to be no galvanic path from either of the two output connections to ground, so you have a floating 10 KV.

The 3D printer, is that grounded?
 

nsaspook

Joined Aug 27, 2009
8,653
Your bleeder resistor works for discharging the stored energy of the PS when off but never trust it completely. A good earth ground on the application device is always a good idea as surface charges can migrate slowly to ungrounded enclosures causing a nasty shock equalizing to ground potential when touched.

Safety should always be a priority when working with lethal potentials.
 

Thread Starter

TechnoDesign

Joined Apr 1, 2021
5
I would earth all metal parts that are not already earthed or otherwise referenced to earth (I am thinking about the ungrounded output of your power supply. , even those "floating" on plastic that can get near the high voltage conductors.

My high voltage experience is mainly 15 kV and up so I might be more cautious (read that as "scared of a shock") than some.

I'm planning to earth the printer frame and all metals to the high voltage ground and having the extruder connected to the HV positive with 2cm distance from the rest of the setup to prevent arcing.

Would it work if I use the return wire of the high voltage as ground? In that case, is there any risk of shock by touching the ground/frame?

Does it seem reasonable? How would you go about earthing it?
 

Thread Starter

TechnoDesign

Joined Apr 1, 2021
5
I'm planning to earth the printer frame and all metals to the high voltage ground and having the extruder connected to the HV positive with 2cm distance from the rest of the setup to prevent arcing.

Would it work if I use the return wire of the high voltage as ground? In that case, is there any risk of shock by touching the ground/frame?

Does it seem reasonable? How would you go about earthing it?
 

nsaspook

Joined Aug 27, 2009
8,653
So I need to replace the AC plug in the picture with a three-pin AC plug with a ground pin. Then connect that input AC ground to the high voltage output return wire. Right? View attachment 234221
If that's the source of the earth ground, then yes. I deal with very high potential and power equipment. Usually the first thing we do is to have a stable 'earth' ground reference for bolting the frame to. This is tied directly into the building ufer ground system and to an electrostatic ground reference sheet in contact and under the equipment.

PXL_20210329_212607676.jpg
500 kev grounding plate for the equipment on top of a grounded mounting platform.
 

Thread Starter

TechnoDesign

Joined Apr 1, 2021
5
If that's the source of the earth ground, then yes. I deal with very high potential and power equipment. Usually the first thing we do is to have a stable 'earth' ground reference for bolting the frame to. This is tied directly into the building ufer ground system and to an electrostatic ground reference sheet in contact and under the equipment.

View attachment 234223
500 kev grounding plate for the equipment on top of a grounded mounting platform.
That's amazing!
I should mention that I'm doing this at home as I don't have access to an equipped HV lab. I have Arc rated gloves, flame-resistant coverall and goggles.

you mentioned: "If that's the source of the earth ground, then yes." Is there anyway to ensure that? The AC input to the power supply has only two wires so I think the AC input and HV DC output are separate from each other.
Is it safe to get the ground from any 3 pin plug and connect that to the negative high voltage output and the printer frame?
 

MaxHeadRoom

Joined Jul 18, 2013
23,596
This is AKA re-referencing Earth GND.
If you want to test an outlet to see if the ground is present, just connect a meter from AC live to the GND terminal, we used to use a test lamp that was connected between the two when doing an installation. ;)
The lamp should light! :cool:
 
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