Motor Bearing Currents - Danfoss VLT FC 300 Operating Instructions Manual

How to Install
3.3.14 Mains Disconnectors, 12-Pulse
Frame size
380-500 V
F9
F9
F9
F9
F11
F11
F11
F11
F13
F13
525-690 V
F9
F9
F9
F9
F11
F11
F11
F13
F13
F13
3.3.15 Motor Insulation
For motor cable lengths ≤ the maximum cable length
listed in the General Specifications tables, 5.1.1 Cable
Lengths and Cross Sections, the following motor insulation
ratings are recommended because the peak voltage can be
up to twice the DC link voltage, 2.8 times the mains
voltage, due to transmission line effects in the motor
cable. If a motor has lower insulation rating, it is
recommended to use a dU/dt or sine wave filter.
Nominal Mains Voltage [V] Motor Insulation [V]
≤ 420
U Standard U
N
420 < U ≤ 500 Reinforced U
N
500 < U ≤ 600 Reinforced U
N
600 < U ≤ 690 Reinforced U
N

3.3.16 Motor Bearing Currents

All motors installed with FC 302 250 kW or higher power
drives should have NDE (Non-Drive End) insulated bearings
installed to eliminate circulating bearing currents. To
minimize DE (Drive End) bearing and shaft currents proper
grounding of the frequency converter, motor, driven
machine, and motor to the driven machine is required.
VLT ® Automation Drive FC 300 12-Pulse
Operating Instructions High Power
Power
P250
P315
P355
P400
P450
P500
P560
P630
P710
P800
P355
P400
P500
P560
P630
P710
P800
P900
P1M0
P1M2
Standard Mitigation Strategies:
= 1300
LL
= 1600
LL
= 1800
LL
= 2000
LL
®
MG34Q202 - VLT is a registered Danfoss trademark
Type
ABB OETL-NF600A
ABB OETL-NF600A
ABB OETL-NF600A
ABB OETL-NF600A
ABB OETL-NF800A
ABB OETL-NF800A
ABB OETL-NF800A
ABB OT800U21
Merlin Gerin NPJF36000S12AAYP
Merlin Gerin NPJF36000S12AAYP
ABB OT400U12-121
ABB OT400U12-121
ABB OT400U12-121
ABB OT400U12-121
ABB OETL-NF600A
ABB OETL-NF600A
ABB OT800U21
ABB OT800U21
Merlin Gerin NPJF36000S12AAYP
Merlin Gerin NPJF36000S12AAYP
1. Use an insulated bearing
2. Apply rigorous installation procedures
- Ensure the motor and load motor are
aligned
- Strictly 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
frequency converter for instance by
screened cable which has a 360°
connection in the motor and the
frequency converter
- Make sure that the impedance from
frequency converter to building ground
is lower that the grounding impedance
of the machine. This can be difficult for
pumps
- Make a direct earth connection between
the motor and load motor
3. Lower the IGBT switching frequency
3 3
45