Danfoss VLT AutomationDrive FC 302 Design Manual

Also see for VLT AutomationDrive FC 302: Service guide Programming guide Instruction manual Installation guide Operating guide

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Danfoss VLT AutomationDrive FC 302 Design Manual Manual pdf 161 page image

Using RCDsWhere residual current devices (RCDs), also known asground leakage circuit breakers, are used, comply with thefollowing:• Use RCDs of type B only as they can detect ACand DC currents.• Use RCDs with a delay to prevent faults due totransient ground currents.• Dimension RCDs according to the system configu-ration and environmental considerations.The leakage current includes several frequenciesoriginating from both the mains frequency and theswitching frequency. Whether the switching frequency isdetected depends on the type of RCD used.130BB958.12f swCable150 Hz3rd harmonics50 HzMainsRCD with low f cut-RCD with high f cut-Leakage currentFrequencyIllustration 10.14 Main Contributions to Leakage CurrentThe amount of leakage current detected by the RCDdepends on the cut-off frequency of the RCD.130BB957.11Leakage current [mA]100 Hz2 kHz100 kHzIllustration 10.15 Influence of the RCD Cut-off Frequency onLeakage Current10.10 IT MainsMains supply isolated from groundIf the drive is supplied from an isolated mains source (ITmains, floating delta, or grounded delta) or TT/TN-S mainswith grounded leg, the RFI switch is recommended to beturned off via parameter 14-50 RFI Filter on the drive andparameter 14-50 RFI Filter on the filter. For more detail, seeIEC 364-3. In the off position, the filter capacitors betweenthe chassis and the DC link are cut off to avoid damage tothe DC link and to reduce the ground capacity currents,according to IEC 61800-3.If optimum EMC performance is needed, or parallel motorsare connected, or the motor cable length is above 25 m(82 ft), Danfoss recommends setting parameter 14-50 RFIFilter to [ON]. Refer also to the Application Note, VLT on ITMains. It is important to use isolation monitors that arerated for use together with power electronics (IEC61557-8).Danfoss does not recommend using an output contactorfor 525–690 V drives connected to an IT mains network.10.11 EfficiencyEfficiency of the drive (ηVLT)The load on the drive has little effect on its efficiency. Ingeneral, the efficiency is the same at the rated motorfrequency fM,N, whether the motor supplies 100% of therated shaft torque or only 75%, in case of part loads.The efficiency of the drive does not change even if otherU/f characteristics are selected. However, the U/f character-istics influence the efficiency of the motor.The efficiency declines slightly when the switchingfrequency is set to a value of above 5 kHz. The efficiency isslightly reduced when the mains voltage is 480 V, or if themotor cable is longer than 30 m (98 ft).Drive efficiency calculationCalculate the efficiency of the drive at different speeds andloads based on Illustration 10.16. The factor in this graphmust be multiplied by the specific efficiency factor listed inthe specification tables in chapter 7.1 Electrical Data, 380–500 V and chapter 7.2 Electrical Data, 525–690 V.1.00.990.980.970.960.950.930.920% 50% 100% 200%0.94Relative Efficiency130BB252.111.01150%% Speed100% load 75% load 50% load 25% loadIllustration 10.16 Typical Efficiency CurvesElectrical Installation Con... Design GuideMG38C202 Danfoss A/S © 01/2018 All rights reserved. 15910 10