Grounding And Pe Conductor Cross-Section - Siemens SINAMICS G130 Engineering Manual

SINAMICS G150
Engineering Information
Cross-section With single
of 3-wire cables routing
2
[mm ]
50 138
70 176
95 212
120 245
150 282
185 323
240 380
300 418
Current-carrying capacity according to DIN VDE 0298 Part 2 at 40° C
With higher amperages, cables must be connected in parallel.
Note:
The recommendations for the North American market in AWG or MCM must be taken from the appropriate NEC
(National Electrical Code)/CEC (Canadian Electrical Code) standards.

Grounding and PE conductor cross-section

The PE conductor must be dimensioned to meet the following requirements:
• In the case of a ground fault, no impermissibly high contact voltages resulting from voltage drops on the PE
conductor caused by the ground fault current may occur (< 50 VAC or < 120 VDC, EN 50 178 Subsection 5.3.2.2,
IEC 60 364, IEC 60 543).
• The PE conductor should not be excessively loaded by any ground fault current it carries.
• If it is possible for continuous currents to flow through the PE conductor when a fault occurs in accordance with
EN 50,178 Subsection 8.3.3.4, the PE conductor cross-section must be dimensioned for this continuous current.
• The PE conductor cross-section should be selected according to EN 60 204-1, EN 60 439-1, IEC 60 364.
Cross-section of the phase
conductor
2
mm
Up to 16
16 to 35
35 and above
Note:
The recommendations for the North American market in AWG or MCM must be taken from the appropriate NEC
(National Electrical Code)/CEC (Canadian Electrical Code) standards.
• Switchgear systems and motors are usually grounded via a separate local ground connection. In the case of a
ground fault with this configuration, the ground fault current is divided and flows through the ground connections in
parallel. With this grounding system, no impermissible contact voltages can occur, despite the PE conductor cross-
sections used in the above table.
Based on experience with different grounding configurations, however, we recommend that the ground wire from
the motor should be routed directly back to the converter. For EMC reasons and to prevent bearing currents,
symmetrical, three-wire, three-phase cables should be used in this case rather than four-wire cables. The ground
connection (PE) must be routed separately or must be arranged symmetrically in the motor cable. The symmetry of
the PE conductor is achieved using a conductor surrounding all phase conductors or using a cable with a
symmetrical arrangement of the three phase conductors and three ground conductors. For further information,
please refer to the sections "Bearing currents caused by steep voltage edges on the motor" and "Line filters" of the
chapter "Fundamental Principles and System Description".
• Through their controllers, the converters limit the load current (motor and ground fault currents) to an rms value
corresponding to the rated current. We therefore recommend the use of a PE conductor cross-section analogous to
the phase conductor cross-section for grounding the converter cabinet.
SINAMICS Engineering Manual – May 2008
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© Siemens AG
With several cables on a
common cable rack
[A] [A]
95
121
146
169
194
222
261
289
Minimum cross-section of the external PE
Minimum phase conductor cross-section
Minimum half the phase conductor cross-section
conductor
2
mm
16