Fi-Protective Switch - Bosch Servodyn-ASC Betriebshandbuch

1.11 FI- Protective
Switch
FI-Protective
Switch
1070066022 - 101
A standard FI- protective switch (puls-current sensitive) may not be used as
the sole protection measure for frequency inverter operation. Frequency
inverter with 3-phase input voltage, with a ground fault of a direct component
in the fault current, can prevent the triggering of a FI- protective switch.
Therefore, according to EN 50178 an FI- protective switch is not permissible
as the sole protective measures are necessary.
Dependant on the available mains form (TN,IT,TT) further protective
measures are necessary. For example, with TN- mains this protection is
through overcurrent protective devices, with IT- mains it is insulation
monitoring with a pulse-code measuring method. A protective separation
can be used with all mains forms as long as the required power and cable
lenghts permit this. The following measures must be taken into account
when selecting the FI- protective switch:
· The standard-FI-protective switch must be correspond to the new
form of construction according to VDE 0664.
· The tripping current should be 300mA or more, in order to prevent
a premature triggering of the inverter by discharge currents (about
200 mA). Dependent on the load, the lenghts of the motor cable and
the use of a radio interference filter, substantially higher leakage
currents can occur.
For single phase voltage supplied frequency inverters (L,N) the only
protection is allowed by a FI-protective switch , when the unit is correspond
to the new form of construction according to VDE 0664.
Universal current sensitive FI-protective switches offer extensive
protection and are permissible as the sole protective measure for
1- and 3- phase frequency inverters. The connection instructions
from the manufacturer must be observed.
Servodyn - ASC
General
GB - 11
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