OPTIMUM
M A S C H I N E N - G E R M A N Y
Assembly and commissioning
Version 1.0 dated 2015-05-27
Page 30
Original operating instructions
F3
GB
3.3.6
Current in the Protective Earth Ground Wire
The degree of the leakage current in the protective earthing conductor depends on whether the
internal EMC filter in the Emerson M200 frequency converter is used for spindle rotation speed
control or not. The standard frequency converter is fitted with an internal EMC filter. Instructions
on how to remove the internal filter is in the converter manual.
With the EMC filter, the leakage current is 15.4 mA AC 230V 50Hz (1 phase supply, phase-
neutral power supply, neutral point earthed).
Without an EMC filter, the leakage current is <1.9 mA (phase-neutral power supply, neutral
point earthed).
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. To
simplify this, the converter is provided with two earth terminals. Both earthing connections are
required to comply with the standard EN 61800-5-1.
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:
There are three common types of FI (ELCB / RCD):
AC - to detect AC fault currents
A - to detect AC fault currents and pulsating DC fault currents (provided the DC current
reaches zero at least once every half cycle).
B - to detect AC fault currents, pulsating DC fault currents and smooth DC residual currents.
Type AC should never be used in converters.
Type A can only be used for single-phase converters.
Type B must be used for 3-phase converters.
When using an external EMC filter, to avoid false error shutdowns, a time delay of at least 50
ms is required. The leakage current can exceed the threshold trigger value for an error shut-
down if the phases are not switched on at the same time.
Line systems
The CNC milling machine is designed for TN and TT line systems with a grounded neutral
point.
Prohibited operation
Operation on TN line systems with grounded external conductors is prohibited.
Operation on TT line systems without grounded neutral points is prohibited.
Operation on IT line systems is not permitted. In an IT line system, all of the conductors are
insulated with respect to the PE protective conductor – or connected to the PE protective con-
ductor through an impedance. Operation on an IT line system is not permitted.
Permissible line supplies
Operation on TN and TT line systems
TN line system
The TN line system in accordance with IEC 60364-1 (2005) transmits the PE conductor to the
installation via a conductor. Generally, in a TN line system the neutral point is grounded There
are versions of a TN line supply with a grounded line the conductor, e.g. with grounded L1.
A TN line system can transfer the neutral conductor N and the PE protective conductor either
separately or combined.
