1.3.1 RCD (FI-Protective Switch)
If personnel protection is required during installation of the system the frequency inverters must be
protected according to EN 50178 (VDE 0160):
– 1-phase inverters by RCD type A (pulse-current sensitive FI's) or type B (all-current sensitive FI's)
– 3-phase inverters (with B6 bridge-connected rectifier) by RCMA's with separation (used privileged)
or RCD's type B (all-current sensitive FI's)
The tripping current should be 300mA or more, in order to avoid a premature triggering of the inverter
by discharge currents (about 200mA).
Dependent on the load, the length of the motor cable and the use of a radio interference filter,
substantially higher leakage current can occur.
The connection instructions from the manufacturer and the valid local reqirements must be observed.
Dependent on the available mains form (TN, IT, TT) further protective measures are necessary in
accordance with VDE Part 410 (Part 4; Chapter 41). For example, with TN-mains this protection is made
with 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 lengths permit this.
Diagram of a distribution board (principle of protective elements)
Mains
To further
distribution lines
Output 1
Output 2
Output 3
Level 1
Level 2
Type
A
To further consumer.They do not
prevent the triggering of the FI
General
RCD
Type A
sel. T
Type
A
To the non-FI compatible
consumer
RCMA/
RCD
Type B
Separation in
accordance
with EN
60947-2
GB - 7
GB