Danfoss VLT AQUA Drive FC 202 Design Manual

Also see for VLT AQUA Drive FC 202: Service guide Installation guide Installation guide Operating guide Installation guide

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7.9 dU/dt TestingTo avoid damage to motors without phase insulationpaper or other insulation reinforcement designed foroperation of the frequency converter, installation of adU/dt filter or LC filter on the output of the frequencyconverter is recommended.When a transistor in the inverter bridge switches, thevoltage across the motor increases by a dU/dt ratiodepending on:• Motor inductance• Motor cable (type, cross-section, length, screened,or unscreened)The natural induction causes an overshoot voltage peak inthe motor voltage before it stabilises. The level dependson the voltage in the DC-link.Peak voltage on the motor terminals is caused by theswitching of the IGBTs. The rise time and the peak voltageaffects the service life of the motor. If the peak voltage istoo high, motors without phase coil insulation can beadversely affected over time.With short motor cables (a few metres), the rise time andpeak voltage are lower. The rise time and peak voltageincrease with cable length.The frequency converter complies with IEC 60034-25 andIEC 60034-17 for motor design.7.9.1 Peak Voltage on MotorTo obtain approximate values for cable lengths andvoltages not mentioned below, use the following “Rules ofThumb”:1. Rise time increases/decreases proportionally withcable length.2. UPEAK = DC link voltage x 1.9(DC link voltage = Mains voltage x 1.35).3.dU /dt = 0.8 ×UPEAKRisetimeData is measured according to IEC 60034-17.Cable lengths are in metres.200–240 V (T2)Cablelength [m]Mainsvoltage[V]Rise time[μsec]UPEAK[kV]dU/dt[kV/μsec]36 240 0.226 0.616 2.14250 240 0.262 0.626 1.908100 240 0.650 0.614 0.757150 240 0.745 0.612 0.655Table 7.32 Frequency Converter, P5K5, T2Cablelength [m]Mainsvoltage[V]Rise time[μsec]UPEAK[kV]dU/dt[kV/μsec]5 230 0.13 0.510 3.09050 230 0.23 0.590 2.034100 230 0.54 0.580 0.865150 230 0.66 0.560 0.674Table 7.33 Frequency Converter, P7K5, T2Cablelength [m]Rise time[μsec]UPEAK[kV]dU/dt[kV/μsec]36 240 0.264 0.624 1.894136 240 0.536 0.596 0.896150 240 0.568 0.568 0.806Table 7.34 Frequency Converter, P11K, T2Cablelength [m]Mainsvoltage[V]Rise time[μsec]UPEAK[kV]dU/dt[kV/μsec]30 240 0.556 0.650 0.935100 240 0.592 0.594 0.807150 240 0.708 0.575 0.669Table 7.35 Frequency Converter, P15K, T2Cablelength [m]Mainsvoltage[V]Rise time[μsec]UPEAK[kV]dU/dt[kV/μsec]36 240 0.244 0.608 1.993136 240 0.568 0.580 0.832150 240 0.720 0.574 0.661Table 7.36 Frequency Converter, P18K, T2Cablelength [m]Mainsvoltage[V]Rise time[μsec]UPEAK[kV]dU/dt[kV/μsec]36 240 0.244 0.608 1.993136 240 0.560 0.580 0.832150 240 0.720 0.574 0.661Table 7.37 Frequency Converter, P22K, T2Cablelength [m]Mainsvoltage[V]Rise time[μsec]UPEAK[kV]dU/dt[kV/μsec]15 240 0.194 0.626 2.58150 240 0.252 0.574 1.929150 240 0.444 0.538 0.977Table 7.38 Frequency Converter, P30K, T2Specifications Design Guide164 Danfoss A/S © 09/2014 All rights reserved. MG20N60277