Rockwell Automation 8720MC High Performance Drives Installation Manual - Manual (Page 67)

Publication 8720MC-IN001D-EN-P — December 2002
Connecting Your 8720MC 3-5
Conduit
For applications above 130 amperes, metal conduit is required for
cable distribution. Follow these guidelines:
• Drives are normally mounted in cabinets, and ground connections
are made at a common ground point in the cabinet. If the conduit
is connected to the motor junction box and the drive end is
connected to the ground panel in the cabinet, you do not need
any additional conduit connections.
• Route no more than three sets of motor leads and a ground wire
through a single conduit. This minimizes cross talk that could
reduce the effectiveness of the noise reduction methods
described. If more than three drive/motor connections per conduit
are required, use shielded cable. If practical, each conduit should
contain only one set of motor leads.
• It is recommended that you use a thick insulation lead wire, such
as type RHW-2 or equal.
General Wire Guidelines
You should observe all applicable safety and national and local
regulations when selecting the appropriate wire size for your system.
Due to the drive overload capacity of 150% of the continuous current
rating for one minute, the conductors for the transformer primary and
secondary must be sized (at a minimum) for 125% to 160% of the
maximum continuous input current for the motor selected. The motor
conductors must also be rated for a minimum of 125% to 160% of the
full load motor continuous current. If less than 150% overload is
required the torque limit parameters must be set in the drive
accordingly. The distance between the drive and motor may affect the
size of the conductors used. To protect against interference, use
shielded wire in motor and control circuits. A shielded cable is
required for all feedback signal wires.
ATTENTION
!
To avoid a possible shock hazard caused by
induced voltages, ground unused wires in the
conduit at both ends. For the same reason, if a
drive sharing a conduit is being serviced or
installed, disable all drives using this conduit.
This eliminates the possible shock hazard from
cross coupled drive motor leads.