do I know the cause for plugging point of SMPS melting in a ups connection

Thread Starter

jraju

Joined Jul 23, 2017
98
Hi, everything worked fine. Suddenly I could smell the melting of wire smell but could not pinpoint that to the smps. The smps was connected to the computer on UPS plug. Ofcourse, my display went out forcing me to look in to it and I found the inner joining point of the smps and the cord, just melted and a simple tab on it just broke the plug plastic cover of the plug.
I immediately switched off and bought a new smps and connected .
May I know, what would have caused the pllug to melt in UPS connection.
 

Ramussons

Joined May 3, 2013
1,395
A bad plug or ups socket causing a poor contact and subsequent heating.
Or loose wire termination to the plug / socket.
My gut feeling is a bad moulded plug of the PC / Monitor.
 

MisterBill2

Joined Jan 23, 2018
17,778
It sounds like you had the external power supply for the computer plugged into the UPS, and then the cord from the computer power supply failed and burned up at the plug.
That could be caused by many of the strands in the wire having broken at the plug, probably due to excess flexing over time.
BUT most computer power cords also pug into the power supply, so probably you could have simply replaced the cord and saved a lot of money. OR, if the cord was wired into the supply, simply cut off the damaged section and installed a replacement plug, and still saved money.
Any engineer should be able to replace a line plug.
 

Thread Starter

jraju

Joined Jul 23, 2017
98
It sounds like you had the external power supply for the computer plugged into the UPS, and then the cord from the computer power supply failed and burned up at the plug.
That could be caused by many of the strands in the wire having broken at the plug, probably due to excess flexing over time.
BUT most computer power cords also pug into the power supply, so probably you could have simply replaced the cord and saved a lot of money. OR, if the cord was wired into the supply, simply cut off the damaged section and installed a replacement plug, and still saved money.
Any engineer should be able to replace a line plug.
Sorry for my late reply. Thanks for all the replies. But i have raised the query because, the ups has power surge protector labelled on all the three plug points. Will this not, cause the power supply to supply only normal power to the parts , ie, smps connected.
 

Reloadron

Joined Jan 15, 2015
7,447
Sorry for my late reply. Thanks for all the replies. But i have raised the query because, the ups has power surge protector labelled on all the three plug points. Will this not, cause the power supply to supply only normal power to the parts , ie, smps connected.
It's not about normal power. My thinking runs with the first two replies. A faulty pin in a connector making poor contact will begin to arc under the current load. The small arcing starts out small but generates a heating effect. This begins what we call a snowball effect where if we roll a snowball down a hill it gets bigger and bigger. As the contact arcs it generates more and more heat as the connection tries to provide the load current. The problem gets larger and larger compounding itself until we see and smell smoke and eventually the connector pin is toasted burned. The heat and burning will work up the wire. It is not about over voltage. It's about a poor connection from your description of the symptoms with the cause being a poor connection point unable to handle a current load.

Make sense?

Ron
 

MisterBill2

Joined Jan 23, 2018
17,778
As soon as the arc starts it produces copper vapor, WHICH IS A VERY GOOD ELECTRICAL CONDUCTOR. THAT is the mechanism for the growing arc effect described. That is how one frayed strand in a 3-phase pug can cause a ball of fire and pop all three of the 15 amp fuses for the outlet. That is very startling, by the way. Also causes burned finger tips.
AND I had the same thing happen a few years back, plugging in a 20-cup coffee pot. The weakened wire failed and a bast of spark shot out of the back of the plug. Quite startling first thing in the morning. That one did not trip the 20 amp breaker, though. Evidently the heater element limited the current, somehow.
 

Thread Starter

jraju

Joined Jul 23, 2017
98
Hi, Reload and Miarwews.
wow. excellent narration to understand the actual cause. I think I was lucky that the damage has not been carried to the inner parts of motherboard etc.
Thanks for letting me know , what arc is and how it damages the connections.
 
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