Rockwell Automation 20L PowerFlex 700L Liquid-Cooled Adjustable Frequency AC Drive User Manual
Page 21
General Installation Information
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PowerFlex 700L Frames 2, 3A, and 3B Liquid-Cooled AC Drives User Manual
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 or
equal to 15 mils (0.4mm/0.015 in.). Use Copper wire only. Wire gauge
requirements and recommendations are based on 75 °C (167 °F). Do not
reduce wire gauge when using higher temperature wire.
Unshielded Cable
THHN, THWN, or similar wire is acceptable for drive installation in dry
environments provided adequate free air space and/or conduit fill rate limits
are used. Do not use THHN or similarly coated wire in wet areas. Any
wire chosen must have a minimum insulation thickness of 15 mils (0.4mm/
0.015 in.) and should not have large variations in insulation concentricity.
Shielded 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 communication/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 the motor can be located from
the drive without the addition of motor protective devices such as terminator
networks. See Chapter 5, “Reflected Wave” in Wiring and Grounding
Guidelines for Pulse Width Modulated (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. Additionally, a braided
shield should be included and 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
®
29528 - 29532 (AWG-1
through AWG-410). This cable has three XLPE insulated conductors plus
ground with a spiral copper shield 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,