Mean Well 100W 12V PSU GND and Earth pin mutual resistance?

[Pythzepf]

Hi!

I'm working with a power supply LRS-100-12. In short it is a 100-230 VAC in 12V 100W out isolated power supply. I discovered by accident (magic smoke involved!) that some of the power supplies measure a resistance between its output GND and the chassis Earth. This value ranges from a few ohms to open (infinite resistance).

As seen in this image taken from the device's datasheet, there is a filter capacitor between GND and Earth. As I understand, this is there to filter out high frequency noise from GND. However the resistance between these pins should measure open, since capacitors present an infinite resistance to DC current/voltage (the voltage injected by multimeter probes in Ohm mode).

Question: is low resistance measured between these pins some anomaly, are some of the PSU's simply defective (or somehow damaged by me), or am I missing something? Thank you!

[Gyro]

What value of resistance are you measuring? It may be that there is a high value discharge resistor wired across the capacitor and not shown on the block diagram.

[coromonadalix]

Normally they are protection device like movs,  sometime blue colored "look a like capacitors"  we have them on some psu's we use,   they are in the "k" ohms value  in my case

In your psu,  you have 3 of them almost in the middle of the psu, you see them thru the grid.


MOV'S tutorial
https://www.electronics-tutorials.ws/resistor/varistor.html

and another one
https://www.nist.gov/sites/default/files/documents/pml/div684/MOV_announce_color.pdf

[shakalnokturn]

AFAIK there's always a capacitor between primary and secondary sides of the transformer.
When a ground connection is provided to the primary side it is a common practise to also link PSU frame and secondary "negative" to ground. (This has the advantage of draining the away the current leaked through the previously mentioned capacitor as it can give you a tingle in the right conditions.)