10-14 Requirements to the Mains Connection Rexroth IndraDrive
DOK-INDRV*-SYSTEM*****-PR02-EN-P
These values, however, can temporally vary quite strongly, according to
the switch status of the mains. The harmonics of the mains voltage
thereby change, too.
Rough estimated values of the mains data are not sufficient for pre-
calculation of the harmonics, as mainly the resonance points always
present in the mains have a strong influence on the harmonics content.
In order to keep the degree of mains voltage harmonics as low as
possible, it is recommended not to connect capacitors or compensation
units (capacitor batteries) directly to the mains, if possible. If absolutely
required, only connect them to the mains via chokes.
10.6 Protection Systems for the Mains Connection
General Information
Protection against contact always depends on the kind and structure of
the supply mains and the mains conditions. For project planning of an
installation, the typical behavior of the loads and supply mains should
always be taken into account.
For protection against contact (indirect contact) in a machine or plant in
which a drive system is used, the overcurrent protective device normally
used is one with protective grounding according to IEC 364 and EN 50178
(Electronic equipment for use in power installations). This is also specified
in UL 508C (Industrial Control Equipment) for North America. Housing
cover or encapsulation by closed housing is used as protection against
direct contact with live conductors.
Fusing by Protective Grounding
Overcurrent protection normally is realized in the form of fuses or
overcurrent release devices (circuit breakers, motor circuit breakers)
installed at the mains connection. For details see fig. 1.
A grounding resistance of 2 Ohm is considered to be sufficient for
grounding.
Overcurrent protection generally is dimensioned or set with a release
current of 1.3 x nominal current of the loads connected to this connection
point.
In the case of an insulation error or a connection between mains phase
and device housing connected to the equipment grounding conductor, the
drive is disconnected from the mains.
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