Siemens Simovert Masterdrives Compendium page 90

05.2003
3.2.3 Industrial and domestic applications
3.2.4 Non-grounded systems
Siemens AG 6SE7087-6QX70 (Version AD)
SIMOVERT MASTERDRIVES
Instructions for Design of Drives in Conformance with EMC Regulations
Limit values are laid down for emitted noise and noise immunity
depending on the application for which the units are envisaged. A
differentiation is made between industrial and domestic environments.
In industrial environments, the noise immunity of the units must be very
high, but lower requirements are made concerning the emitted noise. In
domestic environments, i.e. when connected to public supply systems,
there are strict regulations concerning emitted noise but, on the other
hand, the units can be designed with a lower noise immunity.
If the drive is an integral part of a system, it does not initially have to
satisfy any demands regarding emitted noise and noise immunity.
However, the EMC Law specifies that a system must as a whole be
electromagnetically compatible within its environment. Within the
system, the owner will, in his own interest, make sure that his
equipment is electromagnetically compatible.
Without a radio interference suppression filter, the emitted noise of the
SIMOVERT MASTERDRIVES frequency converters exceeds the limit
value "First environment". Limit values are currently still under
discussion for the "Second environment" sector (see EN 61800-3
section 6.3.2). However, their high noise immunity makes them
insensitive to the noise emitted by units in their vicinity. If all control
components of the system (e.g. automation devices) have a noise
immunity suitable for industrial environments, then it is not necessary
for every drive to maintain this limit value.
In some industrial sectors, non-grounded supplies (IT supplies) are
used to increase the availability of the plant/installation. In the event of
a ground fault, no fault current flows, and the plant can still produce.
However, when a radio interference suppression filter is used, a fault
current will flow when a ground fault occurs, which may cause
shutdown of the drives or even the destruction of the radio interference
suppression filter. In order to minimize this fault current, the radio
interference suppression filter has to be designed differently which will
quickly reach the physical limits. Radio interference suppression filters
additionally affect the concept of non-grounded supply networks and
can thus result in a safety risk when used with these networks (see
Product Standard EN 61800-3: 1996). If required, radio interference
suppression should thus be realized at the grounded primary side of the
supply transformer or with a single special filter at the secondary side.
The special filter also generates leakage currents to ground. A ground-
leakage monitor which is usually used in non-grounded systems has to
be adjusted to the special filter.
Compendium Motion Control
3-3