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I am looking to understand what is the circuit inside a Ground Fault Current Indicator (GFCi). What does the circuit look like?

Simple google search is not yielding good results about the guts of it.

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  • \$\begingroup\$ search "Big Clive GFCI" - in the video he pull one apart and gives a good explanation. \$\endgroup\$ – Jasen Aug 3 '18 at 2:48
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in principal, it can be a high ratio current transformer directly connected to a solenoid that breaks the circuit. Especially in early designs, electronics are often avoided and simplified in circuit interrupting devices. They are designed in as many ways as possible to fail safe, and this is part of the reason a mechanical switch is used.

This is another in depth teardown of a european design.

If you're going to try to build or design a GFCI circuit from scratch for your own interest or education, fine, it's a very interesting device. On the other hand if you want a device on which human safety will depend, buy one that is appropriately rated and certified in the region you live.

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    \$\begingroup\$ "... connected to a solenoid that breaks the circuit" might give the wrong impression. This be more accurate: The solenoid releases a sprung latch which normally holds the circuit breaker closed. The circuit breaker will trip even if the switch is held in the closed position. \$\endgroup\$ – Transistor Aug 3 '18 at 5:26
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    \$\begingroup\$ Yeah. Trying not to overcomplicate. If he watches the videos suggested he'll see two full teardowns of fairly safe modern GFCIS of fairly different design. Just trying to give him an idea of where to start if he wants to build his own. Reminds me I forgot probably the most important part. \$\endgroup\$ – K H Aug 3 '18 at 5:46

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