Rockwell Automation 1336T Wiring and Grounding Guide, (PWM) AC Drives - Manual (Page 72)

72 Rockwell Automation Publication DRIVES-IN001M-EN-P - March 2014
Chapter 4 Best Practices
Signal TB
If an encoder or tachometer feedback is used, a separate terminal block or blocks
is sometimes provided.
Cables terminated here are typically shielded and the signals being carried are
generally more sensitive to noise. Carefully check the user manual for
recommendations on shield termination. Some shields can be terminated at the
terminal block, and other shields are terminated at the entry point.
Moisture Refer to NEC Article 100 for definitions of damp, dry, and wet locations. The
U.S. NEC permits the use of heat-resistant thermoplastic wire in both dry and
damp applications (Table 310-13). However, PVC insulation material is more
susceptible to absorbing moisture than XLPE insulation material (XHHW-2)
identified for use in wet locations. Because the PVC insulating material absorbs
moisture, the corona inception voltage (CIV) insulation capability of the damp
or wet THHN was found to be less than ½ of the same wire when dry. For this
reason, certain industries where water is prevalent in the environment do not use
THHN wire with IGBT drives.
Based on Rockwell Automation research, tests have determined that the cable
type described below is superior to loose wires in dry, damp, and wet applications
and can significantly reduce capacitive coupling and common mode noise:
PVC jacketed, shielded type TC with XLPE conductor insulation
designed to meet NEC code designation cross-linked polyethylene high
heat-resistant water-resistant (XHHW-2) (use in wet locations per the
U.S. NEC, Table 310-13).
Other cable types for wet locations include continuous welded armor cables or
CLX-type cables.
IMPORTANT Consult the user manual for these phase-sensitive connections. Improper
wiring can lead to incorrect drive operation.