Grid Type And Protection; Grid Types; Currents On Protective Earth And Potential Equalization/Leakage Currents - Danfoss iC2-Micro Series Design Manual

Design Guide | iC2-Micro Frequency Converters

Grid Type and Protection

7.3

Grid Types

7.3.1
The drive can operate in different network types with rated network supply voltage:
TN-S
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TN-C
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TN-C-S
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TT
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IT (only supported by C4 version)
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Delta-grounded grids (only supported by C4 version)
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For detailed information about the parameters related to grid types, refer to the application guide.
7.3.2

Currents on Protective Earth and Potential Equalization/Leakage Currents

A properly dimensioned protective earth (PE) setup is essential for the safety of the drive system protecting against electric shock. The PE
connections of the drive installation ensure that the drive system remains safe preventing that single fault currents generate hazardous
voltages on accessible conductive parts, such as conductive enclosure parts.
The drive must be installed according to the requirement for PE connection and supplementary protective bonding as specified in
EN 60364-5-54:2011 cl. 543 and 544. For the automatic disconnection if there is a fault at the motor side, it must be ensured that the
impedance of the PE connection between drive and motor is sufficiently low to ensure compliance to IEC/EN 60364-4-41:2017 cl. 411 or
415. The impedance must be verified by initial and periodic test according to IEC/EN 60364-4-41:2017.
Local requirements may also apply.
Designing the system according to IEC/EN 61800-5-1:2017 ensures the suitability for the connection of PE and protective bonding of
accessible conductive parts according to EN 60364-5-54:2011. When the drive is used as a component inside specific applications, special
requirements for the proper connection to the PE, for example those specified in EN 60204-1:2018 and IEC/EN 61439-1:2021, can apply.
In low-voltage networks currents can arise on the protective conductor (PE) and equipotential bonding conductors and structures
connected to earth potential as an undesirable effect. Since there are different causes for these currents, it is beneficial to know them to
avoid them.
A drive setup consists of a mains supply, the drive inverter, its cabling, and a motor with the load side. Due to the behavior of the active
and passive components and the electrical setup of the installation, several phenomena may appear resulting in currents on the PE
conductor.
Inductive coupling due to asymmetry in mains cables and/or busbars can cause PE current at the mains frequency and its
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harmonics.
Inductive coupling due to asymmetry in motor cables can cause PE current at the motor fundamental frequency.
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As part of the EMI filter DC link, capacitive decoupling to PE can cause PE currents at 150 Hz/180 Hz.
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Voltage distortion/harmonic content on the mains can typically cause PE currents in the 150 Hz–2000 Hz range.
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Common-mode currents due to motor cable capacitance from motor phases to PE typically result in PE currents at the switching
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frequency and harmonics typically above 2 kHz.
The PE current is made up of several contributions and depends on various system configurations:
RFI filtering
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Motor cable length
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Motor cable shielding
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Drive power
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Electrical Installation Considerations
AJ402315027937en-000401 / 130R1239