question on ground/earth diodes

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Hi

Last night i was searching for how most off the peoples solve grounding problems, know i know how it is done, thats not the problem, but the thing i noticed is that the diodes for seperating the ground of the circuit and the earth connention of the chassis ( or outlet offcourse ) are 200V 35A types !!

The 200V i can understand, but the 35A 😕

is there a special reason for that, and if sow would you be sow kind to explain it to me

Greetz Rudy
 
The reason for using the diodes (as opposed to simply lifting the ground from the chassis or using an RC network, etc.) is to allow an extra margin of safety.

If the hot lead of the AC line happens to contact the signal ground, the diodes would kick in and provide a low impedance path to the chassis, which if the chassis is safety grounded, a low impedance path back to the service panel.

The high current rating would allow sufficient current to flow to trip the circuit breaker without the diode blowing up and becoming an open circuit in which case you're back to square one.

se
 
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