Residual-current device

[bonzer]

Hello everybody! Sorry if my question sounds too stupid but it's first time I study about this. I'm not interested in all the details about this type of interrupters but only some aspects. I know they are mainly designed for protection, to react for accidental human contact. Is it the only reason it is used? I mean humans make the current go to the ground so phase and neutral currents become different (enough) and this principle is used to make the attached schematic work. Meanwhile if we have an internal short circuit that isn't touched by human but is danerous for my device, it doesn't react in theory because those windings combined like that are transparent to differential currents equal in norm so it protects only human or from any other phase to ground contact but not from phase to neutral.  To protect my device I should use a fuse or anyway a different structure for my current interrupter. Am I right?

[Zero999]

If there's a short between phase and the earthed case, then it will protect the device, but you're right, a fuse is required to protect against fire from phase to phase or neutral overloads.

Also note that a fuse isn't there to protect the appliance, but the cable. There are few things which are capable of protecting semiconductors inside the device. Slow blow breakers/fuses can protect motors from over-current and thermal fuses/bimetal strips can protect against overheating and fire.