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2. Technical Data
1.5.10 High Frequency Shielding
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.
Ridged metal conduit can be used as the shield of the motor wires. Always
observe the following points :
- remove all paint from the control cabinet and motor housing where the
conduit is fastened
- securely fasten all conduit  ttings
- run only the motor wires through the conduit, all other wires, high voltage AC
and low voltage signal, should be pulled through a separate conduit.
- connect the control panel to the Sub-panel with a heavy ground strap.
If EMI  lters are used, they should be mounted to the inverter 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. Always use the shielding plate provided with the  lter when
connecting the  lter to the inverter.
Shielding of control wires:
If digital signal wires are terminated on a terminal block in the control panel,
the shields should be  rmly connected to the sub-panel on both sides of the
terminal block.
The shields of digital signal wires originating outside the control cabinet which
are not terminated on a terminal block, must be connected to the sub-panel at
the point where the cable enters the control panel and at the inverter.
If the shield is terminated to the sub-panel within 8 inches (20cm) of the
inverter, then the shield no longer needs to be connected to the inverter.
When using un-shielded signal wires, they should always be installed as a
twisted pair (signal and common).
Low voltage signal wires should cross high voltage wires at right angles.
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