Danfoss VLT AQUA Drive Design Manual

Also see for vlt aqua: Instructions Design guide Instruction manual Operating instructions Design guide

Contents

a. Correct groundingControl cables and cables for serialcommunication must be fitted withcable clamps at both ends to ensurethe best possible electrical contact.1b. Wrong groundingDo not use twisted cable ends (pig-tails). They increase the shield impe-dance at high frequencies.1c. Protection with respect toground potential between thePLC and VLTIf the ground potential between theadjustable frequency drive and thePLC (etc.) is different, electric noisemay occur that will disturb the entiresystem. Solve this problem by fittingan equalizing cable next to the con-trol cable. Minimum cable cross-sec-tion: 0.025 in 2 [16 mm 2].1d. For 50/60 Hz ground loopsIf very long control cables are used,50/60 Hz ground loops may occur.Solve this problem by connectingone end of the shield to ground via a100nF capacitor (keeping leadsshort).1e. Cables for serial communica-tionEliminate low-frequency noise cur-rents between two adjustable fre-quency drives by connecting one endof the shield to terminal 61. This ter-minal is grounded via an internal RClink. Use twisted-pair cables to re-duce the differential mode interfer-ence between the conductors.15.9.1. AC Line Supply Interference/HarmonicsAn adjustable frequency drive takes up a non-sinusoidal current from the line power, whichincreases the input current I RMS . A non-sinus-oidal current is transformed by means of aFourier analysis and split up into sine-wavecurrents with different frequencies, i.e., dif-ferent harmonic currents I N with 50 Hz as thebasic frequency:Harmonic currents I1 I 5 I7Hz 50 Hz 250 Hz 350 HzVLT® AQUA Drive Design Guide 5. How to InstallMG.20.N2.22 - VLT® is a registered Danfoss trademark. 1115