Danfoss VLT 380-500 V Design Manual

Contents

Danfoss VLT 380-500 V Design Manual Manual pdf 107 page image

10 Motor10.1 Motor CablesSee chapter 6.10 Cable Specifications for more informationon wire type and sizes.Voltage ratingPeak voltages up to 2.8 times the mains voltage of theVLT® Parallel Drive Modules drive system can occur in themotor cable. High peak voltages can severely stress themotor cable. Use motor cables with rated voltage specifi-cation of at least 0.6/1 kV. Cables in this range providegood resistance to insulation breakdown.DimensionsFollow local codes for current capacity data for cables andconductors. Widely used codes include: NFPA 70, EN60204-1, VDE 0113-1, and VDE 0298-4. Overdimensioningfor harmonics is not required.LengthKeep cables as short as possible. Voltage drop and heatdissipation depends on the frequency and are proportionalto cable length. Consult the cable manufacturer specifi-cations regarding the length and expected voltage dropwhen connected to the drive system. Seechapter 6.10 Cable Specifications.NOTICECABLE LENGTHWith a standard VLT® Parallel Drive Modules drivesystem, shielded cables up to 150 m (492 ft) long orunshielded up to 300 m (984 ft) long provide full voltageat the motor. If this cable length is exceeded, use a sine-wave filter. For information on the selection of a sine-wave filter, refer to the VLT® FC-Series Output Filter DesignGuide.ShieldingSee chapter 9.5 EMC Recommendations for information oneffective shielding.NOTICETWISTED SHIELD ENDS (PIGTAILS)Twisted shield ends increase the shield impedance athigher frequencies, which reduces the shield effect andincreases the leakage current. To avoid twisted shieldends, use integrated shield clamps. Refer toIllustration 10.1.12130BE747.10PEPEPEPE1 Correct grounding of shielded ends2 Incorrect grounding using twisted shield ends (pigtail)Illustration 10.1 Example of Shield Ends10.2 Motor Coil InsulationFor motor cable lengths that are less than or equal to themaximum cable length listed in chapter 6.10 Cable Specifi-cations, use the motor insulation ratings shown inTable 10.1. If a motor has lower insulation rating, Danfossrecommends using a dU/dt or sine-wave filter.Nominal mains voltage Motor insulationUN≤420 V Standard ULL=1300 V420 VN≤ 500 V Reinforced ULL=1600 V500 VN≤ 600 V Reinforced ULL=1800 V600 VN≤ 690 V Reinforced ULL=2000 VTable 10.1 Motor Insulation Ratings10.3 Motor Bearing CurrentsTo eliminate circulating bearing currents in all motorsinstalled with VLT® VLT® AutomationDrive FC 302 90 kW orhigher power frequency converters, install NDE (non-driveend) insulated bearings. To minimize DE (drive end)bearing and shaft currents, ensure proper grounding of thefrequency converter, motor, driven machine, and motor tothe driven machine.Here are some standard mitigation strategies:• Use an insulated bearing.• Follow proper installation procedures.- Ensure that the motor and load motorare aligned.- Follow the EMC Installation guideline.- Reinforce the PE so the high frequencyimpedance is lower in the PE than theinput power leads.Motor Design GuideMG37N102 Danfoss A/S © 6/2016 All rights reserved. 10510 10