Rockwell Automation 1336T FORCE Series B - Manual (Page 249)

Appendix
A
A–1
Appendix
Motor Cables A variety of cable types are acceptable for 1336 FORCE drive
installations. For many installations, unshielded cable is adequate,
provided it can be separated from sensitive circuits. As an approximate
guide, allow a spacing of 1 meter (3.3 feet) for every 10 meters (33 feet)
of length. In all cases, long parallel runs must be avoided.
The cable should be 4–conductor with the ground lead being connected
directly to the drive ground terminal (PE) and the motor frame ground
terminal.
Shielded Cable – Shielded cable is recommended if sensitive circuits
or devices are connected or mounted to the machinery driven by the
motor. The shield must be connected to the drive ground terminal (PE)
and the motor frame ground terminal. It is important that the connection
be made at both ends to minimize the external magnetic field.
If cable trays or large conduits are used to distribute the motor leads for
multiple drives, shielded cable is recommended to reduce or capture the
noise from the motor leads and minimize “cross coupling” of noise
between the leads of different drives. The shield should be connected to
the ground (PE) connections at both the motor and drive end.
Armored cable also provides effective shielding. Ideally it should be
grounded only at the the drive (PE) and motor frame. Some armored
cable has a PVC coating over the armor to prevent incidental contact
with grounded structure. If, due to the type of connector, the armor must
be grounded at the cabinet entrance, shielded cable should be used within
the cabinet to continue as far as possible to the coaxial arrangement of
power cable and ground.
In some hazardous environments it is not permissible to ground both
ends of the cable armor. This is because of the possibility of high current
circulating at the input frequency if the ground loop is cut by a strong
magnetic field. This only applies in the proximity of powerful electrical
machines. In this case, the ground connection at one end may be made
through a capacitance which will block the frequency current but present
a low impedance to RF. Because of the highly pulsed nature of the
circulating current, the capacitor type used must be rated for
AC–to–ground voltage. Consult factory for specific guidelines.
Conduit – If metal conduit is preferred for cable distribution the
following guidelines must be followed:
1. 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, no further
conduit connections are necessary.