0
\$\begingroup\$

I recently purchased a 5V 40A power supply that looks similar to this:

enter image description here

It didn't come with a power cable, so I found one that I wasn't using and stripped the side opposite the three-pronged side (the other side was a female connector that looks like what you'd plug into a computer power supply).

After stripping it, I noticed that there were three wires, each a different color:

  • Green (I assumed this to be ground)
  • White (I assumed this to be neutral)
  • Black (I assumed this to be live)

I screwed the stripped black wire into the L (AC) position, the stripped white wire into the stripped N (AC) position, and the stripped green wire into the position beneath the ground symbol to the right of N (AC).

I plugged the power supply into the wall, and there was a bright, blue light for a fraction of a second, and then nothing. I unplugged it immediately, waited a bit, and tried it again; however, the positions beneath +V were not supplying any voltage, so I assumed it was dead at that point.

After waiting a bit, I opened the power supply cover and noticed that the fuse looked like it wasn't there anymore. I also noticed that the copper for the neutral and ground wires were very close to one-another, but didn't seem to be touching.

What exactly did I do wrong to cause the fuse to burn up?

Did the copper of both the neutral and ground wires being close together cause it to arc, resulting in a short?

\$\endgroup\$
  • \$\begingroup\$ Did you set the line voltage correctly for your country? \$\endgroup\$ – user1850479 Dec 24 '19 at 3:04
  • \$\begingroup\$ @user1850479 Yes, it was set to 110 V by default, and I'm in the US. \$\endgroup\$ – Jacob G. Dec 24 '19 at 3:05
  • \$\begingroup\$ never assume anything ... you should have measured the voltages on the power cord before you cut it, to determine which prong is hot, etc. ... after cutting you should have used an ohmmeter to determine the color of the hot wire \$\endgroup\$ – jsotola Dec 24 '19 at 3:08
  • \$\begingroup\$ To check for output voltage, measure between an "V+" terminal and a "COM" terminal. Sounds like you connected things correctly, but perhaps a loose strand of wire bridged the L and N terminals and burned up when you plugged in the power cord. Is there still power on the outlet you used? \$\endgroup\$ – Peter Bennett Dec 24 '19 at 3:16
  • \$\begingroup\$ @PeterBennett Yes, the outlet itself is fine. \$\endgroup\$ – Jacob G. Dec 24 '19 at 3:17
1
\$\begingroup\$

I would think that most likely the power supply was simply faulty when you got it. Second most likely is that you dropped some conductive detritus into the power supply while you were working on it.

that looks similar to this

The words "looked similar to" are setting off alarm bells here, if you bought a power supply from a reputable vendor you should be able to give us a link or a part number or something! So I would guess you bought this from a less than reputable source.

After stripping it, I noticed that there were three wires, each a different color:

Green (I assumed this to be ground)
White (I assumed this to be neutral)
Black (I assumed this to be live)

That would be the normal american color code. Even if the colors were somehow wrong it would not have resulted in blowing the fuse in an otherwise disconnected power supply (it may have resulted in you getting an electric shock but that is another story).

Did the copper of both the neutral and ground wires being close together cause it to arc, resulting in a short?

A short between neutral and ground is likely to trip a GFCI, but if the installation is otherwise normal it's unlikely to do much beyond that. Even if by some stroke of bad luck live and neutral connections were reversed the fault current would have flowed OUTSIDE the power supply, so it would have had no affect on a fuse INSIDE the power supply.

P.S. I usually use insulated ring crimps on power supplies like these. I find they give a secure result and make the connections more touch-resistant than they would be if bare wires are used (though still far from touch-proof, a power supply like this should be inside an enclosure).

| improve this answer | |
\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.