DSH 432 Protective Impedance versus no-load voltage
http://decisions.iecee.org/icons/ecblank.gif DSH 432
Protective Impedance versus no-load voltage
18f)
60601-1(ed.2);am1;am2
Standard(s)- (year and edition):
IEC 60601-1:1988 Ed.2 Am1+Am2
Sub clause(s): 18f)
Sheet n°: DSH-432
Subject: Protective Impedance versus noload voltage
Key words: Protective, impedance, earth, connection, no-load
Confirmed by CTL at its 39th meeting, in Cologne
Question:
EQUIPMENT for example having a rated current of 30 A require a test current of 1.5 times 30 A.
With a maximum impedance of 0.2 W the voltage drop has to be 9 V (0.2 W * 45 A = 9 V). This is
in contradiction to the required no-load voltage of 6 V maximum.
Decision:
Measuring the protective earth connection has in fact two reasons. It is to determine impedance
and cross-sectional area of protective earth connections. For a measuring current of 25 A both
can be done with one measurement. Requiring a measuring current of more than 25 A it shall be
splitted up into two measurements. In this case, the impedance shall be determined first, using a
voltage not exceeding 6 V.
If cross-sectional area of the protective earth connections cannot be determined as equal to the
one for the phase by measurement of the area, then measurement with current shall be from a
source with a higher voltage than 6 V.
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