Danfoss VLT AutomationDrive FC 302 Instruction 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 Instruction Manual Manual pdf 33 page image

3.4.16 Motor Bearing CurrentsMotors with a rating 110 kW or higher combined withadjustable frequency drives are best with NDE (Non-DriveEnd) insulated bearings to eliminate circulating bearingcurrents caused by motor size. To minimize DE (Drive End)bearing and shaft currents, proper grounding is requiredfor:• Adjustable frequency drive• Motor• Motor-driven machine• Motor to the driven machineAlthough failure due to bearing currents is infrequent, usethe following strategies to reduce the likelihood:• Use an insulated bearing• Apply rigorous installation procedures• Ensure that the motor and load motor arealigned• Strictly follow the EMC Installation guideline• Reinforce the PE so the high frequencyimpedance is lower in the PE than the inputpower leads.• Provide a good high frequency connectionbetween the motor and the adjustable frequencydrive• Ensure that the impedance from adjustablefrequency drive to building ground is lower thanthe grounding impedance of the machine. Makea direct ground connection between the motorand load motor.• Apply conductive lubrication• Try to ensure that the line voltage is balanced toground.• Use an insulated bearing as recommended by themotor manufacturer (note: motors from reputablemanufacturers typically have insulated bearingsas standard in motors of this size).If found to be necessary and after consultation withDanfoss:• Lower the IGBT switching frequency• Modify the inverter waveform, 60° AVM vs.SFAVM• Install a shaft grounding system or use anisolating coupling between motor and load• Use minimum speed settings, if possible.• Use a dU/dt or sinus filterThe electronic thermal relay in the adjustable frequencydrive has received UL-approval for single motor protection,when parameter 1-90 Motor Thermal Protection is set forETR Trip and 1-24 Motor Current is set to the rated motorcurrent (see the motor nameplate).For thermal motor protection, it is also possible to use theMCB 112 PTC thermistor card option. This card provides anATEX certificate to protect motors in explosion hazardareas, Zone 1/21 and Zone 2/22. Whenparameter 1-90 Motor Thermal Protection is set to [20] ATEXETR is combined with the use of MCB 112, it is possible tocontrol an Ex-e motor in explosion hazardous areas.Consult the Programming Guide for details on how to setup the adjustable frequency drive for safe operation of Ex-e motors.3.4.17 Control Cable RoutingTie down all control wires to the designated control cablerouting as shown in Figure 3.19, Figure 3.20, andFigure 3.21. Remember to connect the shields in a properway to ensure optimum electrical immunity.Serial communication bus connectionConnections are made to the relevant options on thecontrol card. For details, see the relevant serial communi-cation bus instructions. The cable must be placed in theprovided path inside the adjustable frequency drive andtied down together with other control wires (seeFigure 3.19 and Figure 3.20).Installation Instruction ManualMG37A222 Danfoss A/S © Rev. 2014-02-07 All rights reserved. 313 3