ABB ACS880-04F, Hardware Manual, Page: 59 / 172

Guidelines for planning the electrical installation 59

Protecting the motor insulation and bearings
The drive uses modern IGBT inverter technology. Regardless of frequency, the drive
output has pulses of approximately the drive DC bus voltage with a very short rise time. Up
to twice bus voltage can be at the motor terminals, depending on the attenuation and
reflection properties of the motor cable and the terminals. The increased voltage can
cause additional stress on the motor and motor cable insulation.
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.
Optional d u /d t 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
The following table shows how to select the motor insulation system and when optional
ABB d
u /d t filters, insulated N-end (non-drive end) motor bearings and ABB common mode
filters are required. Failure of the motor to fulfill the following requirements or improper
installation may shorten motor life or damage the motor bearings and voids the motor
warranty.
Motor type Nominal AC supply
voltage Requirement for
Motor insulation system ABB d u /d t and common mode
filters, insulated N-end motor
bearings
ABB motors
Random-
wound M2_,
M3_ and M4_ U
N
< 500 V Standard + N + CMF
Form-wound
HX_ and AM_ 380 V < U
N
< 690 V Standard P
N
< 500 kW:
+N + CMF
P
N
> 500 kW
+N + d u /d t + CMF
Old* form-
wound HX_
and modular 380 V < U
N
< 690 V Check with the motor manufacturer.
Random-
wound HX_
and AM_ ** 0 V < U
N
< 500 V Enamelled wire with fiber
glass taping + N + CMF
HDP Consult the motor manufacturer.
* manufactured before 1.1.1998
** For motors manufactured before 1.1.1998, check for additional instructions with the motor manufacturer.