Danfoss VLT AutomationDrive FC 360 Design Guide

7.6.4 Motor Insulation
For motor cable lengths that are less than or equal to the maximum cable length listed in chapter Cable Lengths and Cross-sections, use
the motor insulation ratings shown in the following table. If a motor has lower insulation rating, Danfoss recommends using a dU/dt or
sine-wave filter.
Table 14: Motor Insulation Ratings
Nominal mains voltage Motor insulation
U
N
≤420 V Standard U
LL
=1300 V
420 V<U
N
≤500 V Reinforced U
LL
=1600 V
500 V<U
N
≤600 V Reinforced U
LL
=1800 V
600 V<U
N
≤690 V Reinforced U
LL
=2000 V
7.6.5 Motor Bearing Currents
To eliminate circulating bearing currents in all motors installed with the drive, install NDE (non-drive end) insulated bearings. To minimize
DE (drive end) bearing and shaft currents, ensure proper grounding of the drive, motor, driven machine, and motor to the driven
machine.
Standard mitigation strategies:
l Use an insulated bearing.
l Follow proper installation procedures.
¢ Ensure that the motor and load motor are aligned.
¢ Follow the EMC Installation guideline.
¢ Reinforce the PE so the high frequency impedance is lower in the PE than the input power leads.
¢ Provide a good high frequency connection between the motor and the drive. Use a shielded cable that has a 360° connection in
the motor and the drive.
¢ Ensure that the impedance from the drive to building ground is lower than the grounding impedance of the machine. This
procedure can be difficult for pumps.
¢ Make a direct ground connection between the motor and load motor.
l Lower the IGBT switching frequency.
l Modify the inverter waveform, 60° AVM vs. SFAVM.
l Install a shaft grounding system or use an isolating coupling.
l Apply conductive lubrication.
l Use minimum speed settings if possible.
l Try to ensure that the mains voltage is balanced to ground. This procedure can be difficult for IT, TT, TN-CS, or grounded leg systems.
l Use a dU/dt or sine-wave filter.
7.7 Residual Current Devices (RCD) and Insulation Resistance Monitor (IRM)
Use RCD relays, multiple protective earthing, or grounding as extra protection, provided they comply with local safety regulations.
If a ground fault appears, a DC current can develop in the faulty current. If RCD relays are used, local regulations must be observed.
Relays must be suitable for protection of 3-phase equipment with a bridge rectifier and for a brief discharge on power-up. See chapter
Leakage Current for more details.
60 | Danfoss A/S © 2024.01 AJ435824192086en-000101 / 130R1295
Design Guide | VLT® AutomationDrive FC 360

Danfoss VLT AutomationDrive FC 360 Specifications

General

Brand	Danfoss
Model	VLT AutomationDrive FC 360
Category	DC Drives
Language	English