130BB956.12THVD=0%THVD=5%Leakage currentIllustration 2.22 Influence of Line Distortion on LeakageCurrentNOTICEWhen a filter is used, turn off 14-50 RFI Filter whencharging the filter to avoid a high leakage currentmaking the RCD switch.If the leakage current exceeds 3.5 mA, EN/IEC61800-5-1(Power Drive System Product Standard) requires that earthgrounding must be reinforced in one of the followingways:• Earth ground wire (terminal 95) of at least 10mm2• 2 separate earth ground wires both complyingwith the dimensioning rulesSee EN/IEC61800-5-1 and EN50178 for further information.Using RCDsWhere residual current devices (RCDs), also known as earthleakage circuit breakers (ELCBs), are used, comply with thefollowing:• Use RCDs of type B only, capable of detecting ACand DC currents• Use RCDs with an inrush delay to prevent faultsdue to transient earth currents• Dimension RCDs according to the system configu-ration and environmental considerationsSee also Protection Against Electrical Hazards.130BB958.12f swCable150 Hz3rd harmonics50 HzMainsRCD with low f cut-RCD with high f cut-Leakage currentFrequencyIllustration 2.23 Main Contributions to Leakage Current130BB957.11Leakage current [mA]100 Hz2 kHz100 kHzIllustration 2.24 Influence of the Cut-off Frequency of the RCDWhat is Responded to/Measured2.14 Control with Brake Function2.14.1 Selection of Brake ResistorIn certain applications, for instance centrifuges, it isdesirable to bring the motor to a stop more rapidly thancan be achieved through controlling via ramp down or byfree-wheeling. In such applications, dynamic braking with abraking resistor can be utilised. Using a braking resistorensures that the energy is absorbed in the resistor and notin the frequency converter.If the amount of kinetic energy transferred to the resistorin each braking period is not known, the average powercan be calculated based on the cycle time and brakingtime also called intermittent duty cycle. The resistorintermittent duty cycle is an indication of the duty cycle atIntroduction Design Guide36 Danfoss A/S © Rev. 06/2014 All rights reserved. MG20Z20222
