Modern variable speed drives with their fast rising voltage pulses and high switching
frequencies can generate current pulses that flow through the motor bearings. This can
gradually erode the bearing races and rolling elements.
du/dt filters protect motor insulation system and reduce bearing currents. Optional common
mode filters mainly reduce bearing currents. Insulated N-end (non-drive end) bearings
protect the motor bearings.
■ Requirements table
These tables show how to select the motor insulation system and when a drive du/dt and
common mode filters and insulated N-end (non-drive end) motor bearings are required.
Ignoring the requirements or improper installation may shorten motor life or damage the
motor bearings and voids the warranty.
This table shows the requirements when an ABB motor is in use.
Requirement forNominal AC supply
voltage
Motor
type
ABB du/dt and common mode filters, insulated N-end
motor bearings
Motor insula-
tion system
P
N
≥ 350 kW
or
frame size ≥ IEC 400
100 kW ≤ P
N
< 350
kW
or
IEC 315 ≤ frame size
< IEC 400
P
N
< 100 kW
and frame
size <
IEC 315
P
N
≥ 469 hp
or
frame size >
NEMA 580
134 hp ≤ P
N
< 469 hp
or
NEMA 500 ≤ frame
size ≤ NEMA 580
P
N
< 134 hp
and frame
size <
NEMA 500
+ N + CMF+ N-Standard
U
N
≤ 500 V
Random-
wound
M2_, M3_
and M4_
+ N + du/dt + CMF+ N + du/dt+ du/dt
Standard
500 V < U
N
≤ 600 V
or
+ N + CMF+ N-Reinforced
+ N + du/dt + CMF+ N + du/dt+ du/dt
Reinforced
600 V < U
N
≤ 690 V
(cable length ≤
150 m)
+ N + CMF+ N-Reinforced
600 V < U
N
≤ 690 V
(cable length >
150 m)
P
N
< 500 kW:
+N + CMF
+ N + CMFn.a.Standard
380 V < U
N
≤ 690 V
Form-
wound
HX_ and
AM_
P
N
≥ 500 kW +N +
du/dt + CMF
+ N + du/dt with voltages over 500 V + CMF
Check with the
motor manu-
facturer.
380 V < U
N
≤ 690 V
Old
1)
form-
wound
HX_ and
modular
+ N + CMFEnamelled
wire with fiber
glass taping
0 V < U
N
≤ 500 V
Random-
wound
HX_ and
AM_
2)
+ N + du/dt + CMF500 V < U
N
≤ 690 V
Consult the motor manufacturer.HDP
1)
manufactured before 1.1.1998
Guidelines for planning the electrical installation 67