Danfoss VLT 380-500 V Design Manual

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Danfoss VLT 380-500 V Design Manual Manual pdf 117 page image

11 Mains11.1 Mains ConfigurationsThere are several types of AC mains systems for supplyingpower to frequency converters. Each affects the EMCcharacteristics of the system. The 5-wire TN-S systems areregarded as best regarding EMC, while the isolated ITsystem is the least preferred.SystemtypeDescriptionTN mainssystemsThere are 2 types of TN mains distribution systems:TN-S and TN-C.TN-S A 5-wire system with separate neutral (N) andprotective earth (PE) conductors. It provides thebest EMC properties and avoids transmittinginterference.TN-C A 4-wire system with a common neutral andprotective earth (PE) conductor throughout thesystem. The combined neutral and PE conductorresults in poor EMC characteristics.TT mainssystemsA 4-wire system with a grounded neutral conductorand individual grounding of the drive system. It hasgood EMC characteristics when grounded properly.IT gridsystemAn isolated 4-wire system with the neutralconductor either not grounded or grounded via animpedance.Table 11.1 AC Mains Systems and EMC Characteristics11.2 Mains Terminal ConnectionsWhen connecting the mains, observe the following:• Size the wiring based on the input current of thefrequency converter. For maximum wire sizes, seechapter 6.5 Power-dependent Specifications.• Comply with local and national electrical codesfor cable sizes.NOTICEMULTIPLE MAINS CABLESIf connecting more than 1 set of mains terminals, use thesame number, size, and length of cables for each set ofterminals. For example, do not use 1 cable on one mainsterminal and 2 cables on another mains terminal.2-drive module systemsIllustration 10.8 and Illustration 10.9 show the mainsterminal connections for 6-pulse and 12-pulse 2-drivesystems, respectively.• If a common terminal design is used with a 6-pulse, 2-drive system, there is 1 set of mainsterminals.• Common terminal design cannot be used with12-pulse connection of mains in a 2-drive modulesystems. The mains cables are connected directlyto the drive input terminals.• There are individual brake terminals available ineach drive module. Connect an equal number ofrecommended cables to the individual braketerminals.4-drive module systemsIllustration 10.10 shows the mains terminal connections for4-drive systems. If a common terminal design is used, thereis 1 set of mains terminals in each cabinet.11.3 12-pulse Disconnector ConfigurationThis section describes how to use a disconnector for a 12-pulse drive system. When using disconnectors orcontactors, make sure to install an interlock. SeeIllustration 11.1. When installed, both contactors or discon-nectors must close to avoid 1 set of rectifiers not working.Use NC auxiliary contacts with contactors or mains discon-nectors. Connect the interlock in series with the Klixonswitch of the brake. If only 1 contactor/disconnector hasclosed, the LCP shows the error Brake IGBT Fault and doesnot allow the drive system to power the motor.Illustration 11.2 shows a BRF connection with 12-pulsedisconnector and interlock.Mains Design GuideMG37N102 Danfoss A/S © 6/2016 All rights reserved. 11511 11