So between my 220V 50Hz AC source and my 12V 5-10Amps DC load I have placed a SMPS power supply which converts 220V AC to 12V DC and is rated to supply 16Amps. Now my cable to connect the 220V AC with the SMPS power supply is rated for 6Amps. I want to understand whether it is alright or whether I would need that cable to be of a higher Amps rating. And if that is alright then how low could I go in AC Amps rating for the wire when my DC load after the SMPS power supply module continues to pull 5-10Amps DC.

Power Supply

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    \$\begingroup\$ Photograph the label on the power supply and post it here. \$\endgroup\$
    – Andy aka
    Dec 15, 2022 at 8:33
  • \$\begingroup\$ @Andyaka done... \$\endgroup\$ Dec 15, 2022 at 9:29
  • \$\begingroup\$ @Andyaka aah...I get it, it says it draws 1.2 - 1.6 Amps AC \$\endgroup\$ Dec 15, 2022 at 9:30
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    \$\begingroup\$ The AC wire rating depends on the wire thickness. The rating you need depends on how much current goes through the wire. How much current goes through the wire depends on how much the power supply wants. How much the power supply wants depends on how much it is outputting on the DC side. How much it is outputting on the DC side depends on the load. And when I say the needed rating depends on the current - that's only the electronics perspective. Probably the building code says it also depends on the size of the circuit breaker. \$\endgroup\$
    – user253751
    Dec 15, 2022 at 10:51
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    \$\begingroup\$ @DribbleNibble there you go!!! \$\endgroup\$
    – Andy aka
    Dec 15, 2022 at 11:22

1 Answer 1


In ideal situation if you have a power supply that converts 220V to 12V (18.3 times reduction) you will divide current rating by the same factor (so 16A load means 0.87A drawn from AC) In real life you should adjust that for efficiency of your power supply (it is probably higher than 80% anyway) and leave some margin for safety.

In any case your 6A cable should be plenty for this situation.


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