SIMOVERT MV Medium-Voltage Drives 660 kVA to 9100 ... - Industry

SIMOVERT MVEngineering informationEMC – Electromagnetic compatibilityUse and operation (continued)Single-sided groundingof the cable screensFor analog signal cables, whichconduct low signal levels (mV ormA), the cable screen is connectedon one side to thescreen rail in the cabinet (thisavoids ground loops and inductive/parasiticinterference at theline frequency). The open end ofthe screen can then be connectedto the housing througha noise suppression capacitor(e.g. 0.1 mF 100 V MKT).Routing cables¦ All of the signal cables mustbe screened.¦ The signal cables must beseparated in accordancewith signal groups.¦ Cables with digital signalsmay not be routed togetherunscreened next to cableswith analog signals. If sharedsignal cables are used, theindividual signals must bemutually screened.¦ Cables must be routed asclose as possible togrounded sheet steel panels.This reduces noise signalswhich are inductively coupledin.¦ Unnecessary cable lengthsshould be avoided since theyresult in additional couplingcapacitances and couplinginductances.¦ There must be a minimumclearance of > 20 cmbetween signal cables andpower cables below 500 VAC; there must be a clearance> 30 cm to powercables above 1 kV AC.¦ If possible, power cablesshould cross over oneanother at an angle of 90°.Undampened contactorsIt is not permissible to use undampenedcontactors in thedrive converter cabinets. Thus,all of the contactors mounted inthe factory are dampened. Ifundampened contactors areused in an adjacent cabinet,then the cabinets must be partitionedoff using side panels.Contactor coils which are connectedto the same supply networkas the drive converterauxiliary power supply, or locatedclose to the drive converter,must be provided with surgelimiters (RC elements, varistors).Additional cablingAny additional cabling in thecabinet should be kept as shortas possible, and should berouted close to the cabinethousing or mounting panels.Unscreened cables associatedwith the same circuit (outgoingand incoming conductor)should be twisted.System componentsCircuit-breakerThe circuit-breaker, connectedat the primary side of the incomingtransformer, is part ofthe drive converter safety system.If a fault was to occur withinthe drive converter, then theenergy discharged at the faultlocation must be limited. This isrealized as a result of the inductanceof the incoming transformer(V K min = 6%), which limitsthe rate-of-rise and thecircuit-breaker which trips asquickly as possible.In order to guarantee theseconditions, the circuit-breakermust have the following features:¦ The complete release time ofthe circuit-breaker may notexceed 80 ms.¦ The circuit-breaker must beequipped with an undervoltagerelease. The undervoltagerelease (undervoltagecoil) is controlled through therelease circuit, into whichalso the “undervoltagerelease” output of the driveconverter is to be integrated.The power is supplied by theauxiliary voltage (safe supply)of the switching unit.Note:In drive converters, the undervoltagerelease is usuallynot supplied by voltage transformersconnected to themain grid; so undervoltage inthe main grid will not lead toturn-off by the switching unit/ voltage transformer.¦ Additional delay times in thecontrol of the circuit-breakermust be avoided. All commandsfrom the drive converterto the circuit-breakermust act directly without anyrelays involved.¦ There must be one checkbacksignal for the ON statusand for the OFF status of thecircuit-breaker either. Thecheckback signals must notbe delayed, i.e. don’t usecoupling relays.¦ The circuit-breaker musthave an overcurrent-timeprotection.¦ The circuit-breaker must byno means be switched onexternally neither by electricalnor by mechanical control. Amechanical interlock of themanual ON command at thecircuit-breaker prevents thedrive converter from beingdestroyed due to uncoordinatedpower-on.¦ To prevent the drive converterfrom switching offshowing sequential signalswhich cannot be assigned ifthe circuit-breaker is trippedexternally, the drive convertermust be powered off bymeans of a leading contactbefore the main circuitbreakercontacts open. Inaddition, a relating signal(“circuit-breaker external tripping”)is generated/emitted.6Siemens DA 63 · 2004 6/15