Danfoss FC 300 Design Manual

Also see for FC 300: Operating instructions Instruction manual Design guide Design guide Design guide

Contents

Danfoss FC 300 Design Manual Manual pdf 165 page image

9. RS-485 Installation and Set-up9.1. RS-485 Installation and Set-up9.1.1. OverviewRS-485 is a two-wire bus interface compatible with multi-drop network topology, i.e., nodes canbe connected as a bus, or via drop cables from a common trunk line. A total of 32 nodes can beconnected to one network segment.Network segments are divided up by repeaters. Please note that each repeater functions as a nodewithin the segment in which it is installed. Each node connected within a given network must havea unique node address across all segments.Terminate each segment at both ends using either the termination switch (S801) of the adjustablefrequency drives or a biased termination resistor network. Always use shielded twisted pair (STP)cable for bus cabling, and always follow good common installation practice.Low-impedance ground connection of the shield at every node is very important, also at highfrequencies. This can be achieved by connecting a large surface of the shield to ground, by meansof a cable clamp or a conductive cable gland, for example. It may be necessary to apply potential-equalizing cables to maintain the same ground potential throughout the network, particularly ininstallations where there are long lengths of cable.To prevent impedance mismatch, always use the same type of cable throughout the entire net-work. When connecting a motor to the adjustable frequency drive, always use shielded motorcable.Cable: Shielded twisted pair (STP)Impedance: 120 OhmCable length: Max. 3,396 ft [1,200 m] (including drop lines)Max. 1,640 ft [500 m] station-to-station9.1.2. Network ConnectionConnect the adjustable frequency drive to the RS-485 network as follows (see alsodiagram):1. Connect signal wires to terminal 68 (P+) and terminal 69 (N-) on the main control boardof the adjustable frequency drive.2. Connect the cable shield to the cable clamps.NOTEShielded, twisted-pair cables are recommended in order to reduce noise betweenconductors.FC 300 Design Guide 9. RS-485 Installation and Set-upMG.33.B9.22 - VLT® is a registered Danfoss trademark. 1659