14
When working with high frequencies ( > 1kHz ) and power semiconductors
it is recommended to make all ground connections with large exposed metal
surfaces to minimize the 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, CSA 22.1.
All ground connections should be kept as short as possible and as close as
possible to the ground system, 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 lter 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 lter.
Use of shielded cable is recommended when high frequency emissions or
easily disturbed signals are present. Examples are as follows:
• Motor wires: Connect shield to ground at both the drive and 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 shield to ground at both ends.
• Analog control wires: Connect shield to 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 surface of the shield to the ground
point. Connection with a single wire from the braided shield reduces the
effectiveness of the shield 70%. Metal conduit clamps work well for this. Be
sure the t is tight.
1.2.9. Ground
Connections
1.2.10. High Frequency
Shielding
Electrical Connection
To Next Page
Loading...
Need help?
General