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This is a follow-up question to my previous one: I observed that my laptop chargers spark when plugged in and the common elements seems to be power cords with on-off switches (like this one). It seems to me that if the power cord doesn't contain an on-off switch OR if I use a "over-voltage protector" type powercord the charger doesn't spark. In addition I lost 4 power-cords in a short period of time (a couple of months) to - I suspect - the laptop charger.

The power cords lost happened the following way:

  • one shorted out in the middle of the cord an burned a hole
  • one simply shorted out when plugging in (probably at the switch)
  • two shorted out when switching on (they were off, I plugged in the charger and turned them on)

I know for example that economic light-bulbs don't work well together with switches which have lights in them. Could the same be true for laptop chargers?

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... What sort of crappy light bulbs are you used to?! – Ignacio Vazquez-Abrams Oct 18 '11 at 11:15
Seems to be too vague to answer, "lost 4 power cords" does not tell us much. Most all my power bricks spark a little when connecting them to an outlet, this is normal as they have internal components that will draw current for the first few milliseconds, even if they are not connected to anything on the other end. – Moab Oct 18 '11 at 14:51
@IgnacioVazquez-Abrams: Any of the normal CFC lightbulbs will exhibit "weird" behavior (as in: flash from time to time) if connected trough a switch which has "signaling light" (the small red light which shows where the switch is when it is turned off). From what I understand this is because a small current flows trough the light when turned off, which is too low to power a classical light-bulb, but in a CFC the charge builds up and flashes every couple of minutes. – Grey Panther Oct 20 '11 at 7:35
@Moab: I added more details about the power cords lost. – Grey Panther Oct 20 '11 at 7:42

Sparks can occur when there is a poor electrical connection between a plug and an outlet/receptacle during insertion of the plug. If the outlet is switched, turn it off before inserting the plug.

If sparks occur at the outlet when you turn the switch on it means the outlet or plug are defective.

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Thank you for the answer. I tried the "turn it off" method, that's how I lost two of the four power cords (I update the question with the details). – Grey Panther Oct 20 '11 at 7:43
@Cd-MaN: Those power cords seem dangerous badly-manufactured. Are you sure they are rated for the voltage and current used? Since you live in the EU, you should be able to report the leads to your government's equivalent of "Trading Standards" and have the retailer and manufacturer investigated. – RedGrittyBrick Oct 20 '11 at 9:51

There is an almighty great surge when these are first plugged in, or switched on. The sparking/arcing occurs because the contact area is initially small. The current surge could be checked by adding a bulky inductive coil(choke) but that would costs, weight etc.

A laptop cord should take a bit of heat, so if it is melting through it has been abused or there is something wrong with the charger or cord. Switched mode power supplies work by rectifying mains voltage, smoothing it with (low ESR) capacitors and chopping the DC upstream of a regulator. Most are made to take 220-250V so you should not really have an issue at 110V, however those capacitors can explode or rupture, and diodes can fail. The charger will get hot, the cord should not. The stabilised current though the cord should be of the order of 1A, definitely less than 3A.

Where are you buying these ? Maybe change suppliers.

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