Rockwell Automation Publication 520-UM001K-EN-E - August 2021 33
Chapter 1 Installation/Wiring
Use copper wire only. Wire gauge requirements and recommendations are
based on 75 °C. Do not reduce wire gauge when using higher temperature wire.
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. 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. See Reflected Wave in “Wiring and Grounding Guide, (PWM) AC
Drives,” publication DRIVES-IN001
.
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 XLPE insulated conductors with a 100% coverage foil and
an 85% coverage copper braided shield (with drain wire) surrounded by a
PVC jacket.
Other types of shielded cable are available, but the selection of these types may
limit the allowable cable length. Particularly, some of the newer cables twist 4
conductors of THHN wire and wrap them tightly with a foil shield. This
construction can greatly increase the cable charging current required and
reduce the overall drive performance. Unless specified in the individual
WARNING: The distance between the drive and motor must not exceed the
maximum cable length stated in the Motor Cable Length Restrictions Tables in
“Wiring and Grounding Guide, (PWM) AC Drives,” publication DRIVES-IN001.
ATTENTION: Do not use THHN or similarly coated wire in wet areas.
To Next Page
Loading...
Need help?
General
