9
TGH 1360E
3 Principle of operation
IR5002 uses the measuring principle "3-Voltmeter-Method". Asymmetrical as well
as symmetrical insulation faults in IT DC systems can be detected according to
this measuring principle. In combination with the microcontroller a fast, safe
and exact measurement and evaluation can be realized.
In some respect, the measuring time is dependent on the system leakage
capacitances C
E+
and C
E-
(illustrated below). The capacitances are always
recharged when the coupling switches are closed resp. opened.
internal coupling
monitored system
L+
PE
L-
S1
R1.1
Rm1
S2
R2.1
Rm2
RF-
RF+
CE+
CE-
R1
R2
UN
U1
U2
The time delay prevents false trippings during recharging:
•
S1 closed, S2 opened
measuring of the voltage U1 at Rm1
•
S1 opened, S2 closed
measuring of the voltage U2 at Rm2
•
S1 and S2 closed
measuring of the voltage U
N
U
N
= (U1+U2) x
R1+R2
Rm1+Rm2
