Insulation Monitoring - Siemens SINAMICS SH150 Operating Instructions & Installation Instructions

8.3.1.1

Insulation monitoring

The drive is operated in an ungrounded IT supply system. This means that the drive can
continue to operate if just one ground fault occurs.
Note
A second ground fault causes the drive to fail.
For safety reasons, it is necessary to detect such ground faults, in order to eliminate the risk of
electric shock on the drive. This is the reason why the drive is equipped with insulation
monitoring (A-Isometer) that continually monitors the insulation state of the drive including that
of the motor.
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.
Self-test
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.
Terminal monitoring
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.
SINAMICS SH150 6SL3805
Operating Instructions 05/2020
Operation
8.3 Functions
83