I am powering a bunch of LEDs with a 60A/5V power supply. For extra protection, I wired a 50A circuit breaker between the supply and the LED array:


The LEDs started flashing and acting weird so I used a clamp meter to determine the amount of current I was pulling and saw it was a little over 60A. I have an extra breaker and the same thing happened when I switched it out. Am I using the wrong type of breaker?

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    \$\begingroup\$ Have a look at the datasheets Tim vs. Current Trip Curve, it will likely trip within 30-60 minutes. \$\endgroup\$ – PlasmaHH Oct 26 '16 at 14:09
  • \$\begingroup\$ Oh I see. Is there a kind of breaker that will trip much faster? \$\endgroup\$ – user3390169 Oct 26 '16 at 14:13
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    \$\begingroup\$ A fast acting fuse or circuit breaker. Going 60 A on a 50 A one, regardless of type and characteristic is probably still below the trip level. The rated current is stated with margin. You need to read the fine-print in the datasheet. \$\endgroup\$ – winny Oct 26 '16 at 14:15
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    \$\begingroup\$ @user3390169: A fuse is basically there to protect things from catching fire, if you want to protect your LEDs, then a fuse is not necessarily the best solution. \$\endgroup\$ – PlasmaHH Oct 26 '16 at 14:24

The issue is that this circuit breaker is not designed to trip quickly at just 120% of it's rated current. Consider the graph below:

enter image description here

It is fairly clear, both graphically and with the information in the tables, that the breaker will not trip for at least an hour at 60A.

If you are trying to current-limit your LEDs continuously, a circuit breaker is not the right approach. You either need a current-limiting resistor or some sort of active control, and either way you'll have to dissipate the excess energy as heat. If all you are trying to do is add protection to the circuit against faults, consider a fast-acting fuse or just a more suited circuit breaker.

As for the odd behavior you saw with the LEDs, my best guess is that your power supply was trying to compensate for an over-voltage or over-current condition, and was scaling down either the current or voltage respectively.

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