>From another angle: When is a circuit considered NOT connected to earth ground? In other words, if the only connections to earth in a SELV circuit are through isolating components such as 3kV capacitors (from point B to PE in the drawing), is that circuit considered unearthed? I understand that a circuit isolated from protective earth by optos and relays is considered unearthed.
Thanks, Jack Netaccess, Inc. > -----Original Message----- > From: [email protected] > Sent: Tuesday, July 14, 1998 1:08 PM > To: [email protected] > Subject: Re: protective earth > > Alan, > > You asked: > >When considering the protectively earthed SELV circuit below are > >all points of the circuit (A,B and C) deemed to be connected to > >protective earth or just the current return leg. > > Yes, all points (A, B & C) depicted in the circuit in your drawing > are, in > fact, electrically connected to earth. They may not be directly > connected as C > is in this case, but all are electrically connected nonetheless. It > is > important to note here that each circuit [NOT EACH POINT IN A > CIRCUIT] is > "deemed" to be connected to earth if earth is connected to an > appropriate point > (usually a single point) in each circuit (e.g., the circuit supply > return leg). > Earthing requirements of IEC60950 referred to in previous emails of > this thread > must also be met, if your product is ITE. > > I hope this clears this up as this concept draws on fundamental > circuit theory. > > The above represents only my humble opinion. > > Comments? > > Best regards, > Ron Pickard > [email protected] >
