Rockwell Automation 20A PowerFlex 70 Adjustable Frequency AC Drive User Manual
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Rockwell Automation Publication 20A-IN009D-EN-P - June 2013
PowerFlex 70 Adjustable Frequency AC Drive
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. Use shielded cable for installations with
sensitive equipment such as weigh scales, capacitive proximity switches, and other
devices that can 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 can also help reduce shaft voltage and induced bearing currents for
some applications. In addition, the increased impedance of shielded cable can
help extend the distance that the motor can be 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,
publicatio
Consider the general specifications of the environment of the installation,
including temperature, flexibility, moisture characteristics, and chemical
resistance. In addition, a braided shield can 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 295
xx (xx determines gauge).
This cable has four Cross-linked Polyethylene (XLPE) insulated conductors with
a 100% coverage foil and an 85% coverage copper braided shield (with drain
wire) surrounded by a Polyvinyl Chloride (PVC) jacket.
Other types of shielded cable are available, but the use of these types can limit the
allowable cable length. For example, some of the newer cables bundle four
conductors of THHN wire and wrap them tightly with a foil shield. This type of
construction can greatly increase the cable charging current that is required and
reduce the overall drive performance. Unless specified in the individual distance
tables as tested with the drive, these cables are not recommended and their
performance against the lead length limits is not known.
Table 7 - Recommended Shielded Wire
Location
Rating/Type
Description
Standard
(option 2)
Tray rated 600V, 90 °C
(194 °F) RHH/RHW-2
Anixter OLF-7xxxxx or
equivalent
Three tinned copper conductors with XLPE insulation.
5 mil single helical copper tape (25% overlap minimum) with three bare
copper grounds in contact with the shield.
PVC jacket.
Class I and II;
Division I and II
Tray rated 600V, 90 °C
(194 °F) RHH/RHW-2
Anixter 7V-7xxxx-3G
or equivalent
Three bare copper conductors with XLPE insulation and impervious
corrugated continuously welded aluminum armor.
Black sunlight resistant PVC jacket overall.
Three copper grounds on #10 AWG and smaller.
ATTENTION: To avoid a possible shock hazard caused by induced voltages,
unused wires in the conduit must be grounded at both ends. Also, if a drive
sharing a conduit is being serviced or installed, disable all of the drives that are
using that conduit. This helps minimize the possible shock hazard from cross
coupled motor leads.