66 Guidelines for planning the electrical installation
Motor cable shield
If the motor cable shield is used as the sole protective earth conductor of the motor, make
sure that the conductivity of the shield is sufficient. See subsection General rules above, or
IEC 61439-1. To effectively suppress radiated and conducted radio-frequency emissions,
the cable shield conductivity must be at least 1/10 of the phase conductor conductivity.
The requirements are easily met with a copper or aluminum shield. The minimum
requirement of the motor cable shield of the drive is shown below. It consists of a
concentric layer of copper wires with an open helix of copper tape or copper wire. The
better and tighter the shield, the lower the emission level and bearing currents.
Armored cable / shielded power cable
Six conductor (3 phases and 3 ground) type MC continuous corrugated aluminum armor
cable with symmetrical grounds is available from the following suppliers (trade names in
parentheses):
• Anixter Wire & Cable (Philsheath)
• BICC General Corp (Philsheath)
• Rockbestos Co. (Gardex)
• Oaknite (CLX).
Shielded power cables are available from Belden, LAPPKABEL (ÖLFLEX) and Pirelli.
Planning the braking system
See chapter Resistor braking.
Selecting the control cables
Shielding
All control cables must be shielded.
Use a double-shielded twisted pair cable for analog signals. We recommend this type of
cable for the pulse encoder signals also. Employ one individually shielded pair for each
signal. Do not use common return for different analog signals.
1 Insulation jacket
2 Copper wire screen
3 Helix of copper tape or copper wire
4 Inner insulation
5 Cable core
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