Inexpensive Duwi extension cords are sold in many Russian stores and on Internet sites. And Auchan this extension cord with a three-meter wire and four sockets with grounding costs 320 rubles.
I studied this extension and checked what the cores of the cable are made of (spoiler: not copper).
The extension cord is sold in a stretch pack.
The label indicates a maximum load of 2200 W/10 A.
There is an inscription “10/230 ~ MAX 2200W” on the plastic of the socket block.
The inscription on the wire: “H05VV-F 3G 0.75mm²”.
On the plastic of the plug there is an inscription “10/230~”, phase (L), zero (N) and ground contacts are indicated.
The plastic housing of the socket block burns well.
The length of the wire from the point of exit from the plug to the point of entry into the socket block is 2 meters 97 cm.
Distance from the center of the socket closest to the wire to the center of the plug: 3 meters 6 cm.
To check the operation of the extension cord in the maximum load mode, a current of 10 A was passed through it.
After 30 minutes, the temperature of the outer sheath of the cable reached 58°C.
Due to incorrect installation (see below), the temperature of the wires inside the extension reaches 63°C.
Significant heating of the plug and contacts of the socket block was not recorded.
Resistance from plug contact to nearest socket block contact:
First line: 153.6 mΩ;
Second line: 158.3 mΩ;
Ground line: 178.1 mΩ.
This is too high a resistance for a copper wire, so you will have to study the wires separately.
The wires consist of 25 wires. Each wire has a diameter of 0.18 mm (wire cross section approx. 0.64 mm²).
The resistance of the cores in a segment of 1 m 52 cm of wire was:
Brown wire: 73.7 mΩ (48.5 Ω/km).
Blue wire: 76.4 mΩ (50.3 Ω/km).
Yellow-green wire: 75.0 mOhm (49.3 Ohm/km).
This resistance corresponds to a copper conductor cross section of 0.35 mm²
The strands are made of an unknown alloy, but are not magnetic, so it’s not steel.
When the wires are heated with a lighter, their color changes from copper to gray.
The socket block is collapsible, its two halves are fastened with six self-tapping screws with triangular heads.
The anti-crease sleeve is missing. The wires are soldered to the bars. The case has three slots for three wires, but all the wires are routed through one slot, which caused the wires to be squeezed and there was increased heating at the maximum load current.
Contact strips have a thickness of 0.4 mm, the metal is magnetized. Grounding strips are riveted to the busbar.
This is far from the worst extension cord on the market. Although its wires are not made of copper, they withstand the declared load. If not for the pinched wires, one could say that the build quality is quite decent. Such an extension cord can be used, but I do not recommend leaving it plugged in unattended, because the plastic of its case is combustible.