Version 1.0 - 2020-9-4
19
Translation of original operating manual
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3.9.1
Regulated drives in connection with residual current devices
Speed-controlled drives are one of the standard equipment in machine and plant construction
and perform various tasks. Compared to a simple motor, the electronic rectifiers or converters
require some special features for the necessary safety measures for electrical safety. Depend-
ing on the application, the use of a fault current protection device, differential current monitor-
ing or insulation monitoring can make more sense.
For electrical safety, DIN VDE 0100-410 (VDE 0100 part 410): 1997-01 "Erection of heavy cur-
rent installations up to 1000V" is a basic standard. It describes both, the admissible net forms
and the necessary protective measures against dangerous body currents. Based on this stand-
ard DIN EN 50178 (VDE 0160): 1998-04 "Equipping of heavy current systems with electronic
equipment" specifies the protective measures to be applied to controlled drives in more detail. It
calls for: "In the case of electronic equipment, the protection of persons against dangerous
body currents must be carried out in such a way that a single fault does not cause any danger."
Regulated drives with residual current devices
The TN-S system is the most common network form for the operation of controlled drives. This
is done, among other things, for EMV reasons and to avoid vagabonding currents. In accord-
ance with DIN VDE 0100-410 (VDE 0100-410): 1997-01, fault current protective devices
(ELCB) can be used as a protective measure against dangerous body currents. According to
DIN VDE 0100-482 (VDE 0100 part 482): 2003-06 "Electrical installations of buildings", cables
and wiring systems in fire-endangered plants must be protected by ELCBs with a rated differen-
tial current of 300 mA. According to IEC 60755, ELCBs differ in the type of fault currents they
can detect. In conjunction with electronic devices currents with DC components may occur.
3.9.2
Protection from Dangerous Shock Currents, use of ELCBs
To achieve increased safety in all installation systems, and in power supply ranges for which
the installation provisions stipulate or recommend the ELCB devices.
Measure for “Protection from Dangerous Shock Currents”, as regulated in DIN VDE 0100 Part
410. All measures are to be mentioned:
Protection from indirect contact – as protection against fault by shutting down in the event of
inadmissibly high contact voltage by short circuit shock on the operating resource.
Protection from direct contact – as additional protection by shutting down in the event of
contact with a live conductor. Dangerous shock currents are shut down within the shortest
possible time, if the rated fault current of the circuit breaker is 30 mA (e.g. Domestic
environment), for a personal protection system 10 mA (e.g Bathroom).
Fire prevention – Prevention of the origination of electrically-ignited fires if the rated fault
current of the circuit breaker is 300 mA. Operating premises at risk of fire to VdS 2033:
2002-02 300 mA (e.g. Factory halls).
3.9.3
Current in the protective earth conductor - Leakage current
With EMC filters in frequency converters, the leakage current is always greater than 3.5 mA
due to physics. Some types of frequency converters also achieve a leakage current of up to
300mA.
Therefore, a fixed earth connection is required and the minimum cross section of the protective
earthing conductor must conform to local safety regulations for devices with high leakage cur-
rent. This is achieved by providing a permanent fixed earthing connection with two independ-
ent conductors, each having a cross section the same as the power supply cord or greater.
Preferably, machines with frequency converters are therefore to be permanently connected to a
terminal box, otherwise an additional fixed earth connection is required, which is not routed
over the plug, and must correspond to at least the cross-section of the cable in the plug.
Since a direct current may be caused by the frequency converter in the protective earthing con-
ductor, if an upstream residual current device (ELCB / RCD) is required in the network, the fol-
lowing guidelines must be followed: