Planning the electrical installation68Selecting the control cablesAll control cables must be shielded.As a general rule, the control signal cable shield should be earthed directly in theACS800-67. The other end of the shield should be left unconnected or earthedindirectly via a high frequency, high voltage capacitor of a few nanofarads(e.g. 3.3 nF / 3000 V). The screen can also be earthed directly at both ends if theyare in the same earth line with no significant voltage drop between the end points.Use a double shielded twisted pair cable (see figure a) for analogue signals. Thistype of cable is recommended for the pulse encoder signals also. Employ oneindividually shielded pair for each signal. Do not use common return for differentanalogue signals.A double shielded cable is the best alternative for low voltage digital signals butsingle shielded twisted multipair cable (figure b) is also usable.Run analogue and digital signals in separate, shielded cables.Relay controlled signals, providing their voltage does not exceed 48 V, can be run inthe same cables as digital input signals. It is recommended that the relay controlledsignals be run as twisted pairs.Never mix 24 VDC and 115/230 VAC signals in the same cable.Relay cableThe cable type with braided metallic screen (e.g. ÖLFLEX LAPPKABEL, Germany)has been tested and approved by ABB.Coaxial cable (for use with Advant Controllers AC 80 / AC 800M)• 75 ohm• RG59, diameter 7 mm or RG11, diameter 11 mm• Maximum cable length: 300 m (1000 ft)aDouble shielded twisted multipaircablebSingle shielded twisted multipaircable
