Yaskawa MP920 Communications Module - Manual (Page 309)

D.3 Outdoor Panel-to-Panel Wiring
D-17
D
D.3 Outdoor Panel-to-Panel Wiring
D.3.1 Wiring Precautions
The procedure for laying communications cables is based on the procedure described in D.2
Indoor Panel-to-Panel Wiring , but heed the following precautions.
• For outdoor wiring, always lay the communications cables along an above-ground struc-
ture such as steel frames (see Fig. D.11 (a) below).
• Where there is no above-ground structure, house the communications cables in an under-
ground pit or tunnel, or bury them in the ground (see Fig. D.11 (b) and (c) below).
• Do not lay bare communications cables overhead. Otherwise, the cables will collect
inductive noise from electric waves in the air and cause transmission errors.
• The transmission system is not protected against lightning surge. If the communications
cables are laid overhead, the equipment may be damaged due to lightening.
• Communications cables expand according to the surrounding temperature. Generally, the
temperature coefficient of communications cables is approximately 0.05% per 10 °C.
For example, a 500-meter communications cable expands 25 cm when the temperature
increases 10
°C. Normally, this amount of expansion can be absorbed within the cabling
route. However, where communications cables are laid along above-ground structure, the
temperature difference will be considerably large and cable expansion or contraction
may not be absorbed within the cabling route. To prevent this, the communications
cables must be given some play so that their expansion and contraction can be absorbed
within the route.
• If the communications cables are housed in a metal wiring conduit or duct, water will be
trapped inside the conduit or duct and apply mechanical stress to the communications
cables when frozen in winter. To prevent this, provide the conduit or duct with drain
holes.