Ground Connections; High Frequency Shielding - KEB COMBIVERT F5 Reference Manual

2.2.9 Ground
Connections
2.210 High Frequency
Shielding
When working with high frequencies (> 1kHz) and power semiconductors, it
is recommended to make all ground connections with large exposed metal
surfaces to minimize ground resistance.
The metal sub-plate the inverter is mounted on is regarded as the central ground
point for the machine or the equipment. For best results, use an unpainted,
galvanized, or plated sub-panel.
An additional high-frequency ground wire should be connected between the
inverter and the sub-panel. Use a stranded wire equal in size to the main line
conductor or a thick ground strap. This is in addition to the ground wire required
by NFPA 70, UL 508, and CSA 22.1.
All ground connections should be kept as short as possible and as close as
possible to the ground system, and sub-panels.
If other components in the system exhibit problems due to high-frequency
disturbances, connect an additional high-frequency ground wire between
them and the sub-panel.
The EMI filter should be mounted to the drive or as close as possible to the
inverter and on the same sub-panel as the inverter. Good metallic surface
contact to the sub-panel is required to provide adequate high-frequency
grounding of the filter.
Use of shielded cable is recommended when high frequency emissions or
easily disturbed signals are present. Examples are as follows:
• Motor wires: Connect the shield to the ground at both the drive and the
motor. NOTE the shield should never be used as the protective ground
conductor required by NFPA70 or CSA22.1. Always use a separate
conductor for this.
• Digital control wires: Connect the shield to the ground at both ends.
• Analog control wires: Connect the shield to the ground only at the inverter.
The connection of meshed shields to the ground connection should not be done
through a single strand or drain wire of the shield but with metallic clamps to
provide 360° contact around the shield's surface to the ground point. Connection
with a single wire from the braided shield reduces the effectiveness of the
shield by 70%. Metal conduit clamps work well for this. Be sure the fit is tight.
Electrical Connection
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