Only one A-Isometer can be connected to each live connected IT system. The A-Isometer
adjusts monitoring in line with the line discharge capacitance. The A-Isometer is connected
between the ungrounded line supply and the equipotential bonding conductor (PE).
For the duration of testing, disconnect the instrument cables of the A-Isometer when performing
any insulation or voltage testing on the power system.
The A-Isometer performs an automatic self-test under the following conditions:
● When the insulation resistance of the line supply > 20 MΏ
● Every 24 hours when an output relay for the system error message has been preselected.
The connections to mains and ground (PE) are monitored continuously. If the cables are
interrupted or not connected, or if their resistance is high, this is indicated on the LCD. In this
case, please check the terminal conductors immediately, as the insulation resistance is not
being measured properly.
The insulation resistance can be > 20 MΏ in new or small IT systems. To suppress the
message, disable the connection monitoring in Setup2. The A-Isometer monitors the insulation
resistance of the drive.
The following limit values are monitored:
● Limit value 1: Insulation resistance < 500 kΩ = Signal 1 (alarm)
● Limit value 2: Insulation resistance < 100 kΩ = Signal 2 (fault)
The signals are issued to STARTER and output on the operator panel. Further information
about the wiring is contained in the circuit manual.
Tripping of the circuit-breaker in case of undervoltage
If a serious fault occurs (e.g. overload in the DC link), the drive is immediately disconnected
from the power supply by means of the safety shutdown function.
This function cannot ensure that the drive stops immediately, nor can it ensure that residual
voltages do not still exist at the output terminals and within the unit.
High voltages can cause death or serious injury if the safety rules are not observed or if the
equipment is handled incorrectly.
Always carefully observe the "five safety rules (Page 13)".
The shutdown of the circuit-breaker is triggered by a safety contactor combination.
SINAMICS SM120 6SL38715
Operating Instructions 07/2015