Danfoss VLT AQUA Drive FC 202 Design Manual

Also see for VLT AQUA Drive FC 202: Service guide Installation guide Installation guide Operating guide Installation guide

Contents

7 RS-485 Installation and Set-up7.1 IntroductionRS-485 is a 2-wire bus interface compatible with multi-dropnetwork topology. Nodes can be connected as a bus, orvia drop cables from a common trunk line. A total of 32nodes can be connected to one network segment.Repeaters divide network segments. Note each repeaterfunction as a node within the segment in which it isinstalled. Each node connected within a given networkmust have a unique node address, across all segments.Terminate each segment at both ends, using either thetermination switch (S801) of the frequency converters or abiased termination resistor network. Always use screenedtwisted pair (STP) cable for bus cabling, and always followgood common installation practice.Low-impedance earth connection of the screen at everynode is important, including at high frequencies. Thus,connect a large surface of the screen to earth, e.g. with acable clamp or a conductive cable gland. If necessary,apply potential-equalizing cables to maintain the sameearth potential throughout the network. Particularly ininstallations with long cables.To prevent impedance mismatch, always use the sametype of cable throughout the entire network. Whenconnecting a motor to the frequency converter, always usescreened motor cable.Cable Screened twisted pair (STP)Impedance 120 ΩCable length Max. 1,200 m (including drop lines)Max. 500 m station-to-stationTable 7.1 Motor Cable7.1.1 Hardware SetupUse the terminator dip switch on the main control boardof the frequency converter to terminate the RS-485 bus.1 2S801ON130BA272.11Illustration 7.1 Terminator Switch Factory SettingNOTICEThe factory setting for the dip switch is OFF.7.1.2 Parameter Settings for ModbusCommunicationThe parameters in Table 7.2 apply to the RS-485 interface(FC-port)Parameter Function8-30 Protocol Select the application protocol to run onthe RS-485 interface8-31 Address Set the node address. Note: The addressrange depends on the protocol selected in8-30 Protocol8-32 Baud Rate Set the baud rate. Note: The default baudrate depends on the protocol selected in8-30 Protocol8-33 Parity / StopBitsSet the parity and number of stop bits.Note: The default selection depends on theprotocol selected in 8-30 Protocol8-35 MinimumResponse DelaySpecify a minimum delay time betweenreceiving a request and transmitting aresponse, which can be used forovercoming modem turnaround delays.8-36 Max ResponseDelaySpecify a maximum delay time betweentransmitting a request and receiving aresponse.8-37 MaximumInter-Char DelaySpecify a maximum delay time betweentwo received bytes to ensure timeout whentransmission is interrupted.Table 7.2 Modbus Communication Parameters7.1.3 EMC PrecautionsTo achieve interference-free operation of the RS-485network, the following EMC precautions are recommended.Relevant national and local regulations, regardingprotective earth connection, for example, must beobserved. The RS-485 communication cable must be keptaway from motor and brake resistor cables to avoidcoupling of high-frequency noise from one cable toanother. Normally a distance of 200 mm (8 in) is sufficient.However, in situations where cables run in parallel overlong distances, keeping the greatest possible distancebetween cables is recommended. When crossing isRS-485 Installation and Set... Design Guide148 Danfoss A/S © Rev. 06/2014 All rights reserved. MG20Z20277