Rockwell Automation Publication 22C-UM001J-EN-E - January 2017
23
Installation/Wiring
Chapter 1
Motor Cable Types Acceptable for 200...600 Volt Installations
A variety of cable types are acceptable for 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 0.3 meters (1
foot) for every 10 meters (32.8 feet) of length. In all cases, long parallel runs
must be avoided. Do not use cable with an insulation thickness less than 15
mils (0.4 mm/0.015 in.). Do not route more than three sets of motor leads in a
single conduit to minimize “cross talk”. If more than three drive/motor
connections per conduit are required, shielded cable must be used.
UL installations must use 600V, 75°C or 90°C wire.
Use copper wire only.
Unshielded
THHN, THWN or similar wire is acceptable for drive installation in dry
environments provided adequate free air space and/or conduit fill rates limits
are provided.
Do not use THHN or similarly coated wire in wet areas.
Any
wire chosen must have a minimum insulation thickness of 15 mils and should
not have large variations in insulation concentricity.
Shielded/Armored Cable
Shielded cable contains all of the general benefits of multi-conductor cable
with the added benefit of a copper braided shield that can contain much of the
noise generated by a typical AC Drive. Strong consideration for shielded cable
should be given in installations with sensitive equipment such as weigh scales,
capacitive proximity switches and other devices that may be affected by
electrical noise in the distribution system. Applications with large numbers of
drives in a similar location, imposed EMC regulations or a high degree of
communications /networking are also good candidates for shielded cable.
Shielded cable may also help reduce shaft voltage and induced bearing currents
for some applications. In addition, the increased impedance of shielded cable
may help extend the distance that the motor can be located from the drive
without the addition of motor protective devices such as terminator networks.
Refer to Reflected Wave in “Wiring and Grounding Guidelines for PWM AC
Drives,” publication
Consideration should be given to all of the general specifications dictated by
the environment of the installation, including temperature, flexibility, moisture
characteristics and chemical resistance. In addition, a braided shield should be
included and be specified by the cable manufacturer as having coverage of at
least 75%. An additional foil shield can greatly improve noise containment.
A good example of recommended cable is Belden® 295xx (xx determines
gauge). This cable has four (4) XLPE insulated conductors with a 100%
coverage foil and an 85% coverage copper braided shield (with drain wire)
surrounded by a PVC jacket.
