A-BAdjustable 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. 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 

DRIVES-IN001A-EN-P.

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.

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 distance tables as tested with the drive, 

these cables are not recommended and their performance against the lead 

length limits supplied is not known.