Selection Of Winding Insulation With Frequency Converters; Thermal Protection Of Windings; Bearing Currents; Elimination Of Bearing Currents - ABB M3JM Betriebsanleitung

6.3.3 Selection of winding insulation with
frequency converters
The selection of winding insulation and filters can be made
according to table below:
Nominal supply
voltage U of
N
the converter Winding insulation and filters required
≤ 500 V
U ABB Standard insulation
N
≤ 600 V
U ABB Standard insulation + dU/dt filters
N
OR
ABB Special insulation
(variant code 405)
≤ 690 V
U ABB Special insulation
N
(variant code 405)
AND
dU/dt-filters at converter output
6.4 Thermal protection
of windings
All cast iron Ex -motors are equipped with PTC thermistors
to prevent the winding temperatures exceeding the
thermal limits of used insulation system. In all cases it is
recommended to connect them.
NOTE!
If not otherwise indicated on the rating plate, these
thermistors do not prevent motor surface temperatures
exceeding their temperature classes (T4 or T5).
ATEX-countries:
If the motor certificate requires, the thermistors must be
connected to a thermistor circuit relay functioning indepen-
dently and that is dedicated to reliably trip off the supply to
the motor according to the requirements of the "Essential
Health and Safety Requirements" in Annex II, item 1.5.1 of
the ATEX Directive 94/9/EC or 2014/34/EU.
Non-ATEX countries:
It is recommended that the thermistors are connected to a
thermistor circuit relay functioning independently and that
is dedicated to reliably trip off the supply to the motor.
NOTE!
According to the local installation rules, it may be
possible to also connect the thermistors to equipment
other than a thermistor relay; for example, to the
control inputs of a frequency converter.

6.5 Bearing currents

Bearing voltages and currents must be avoided in all
variable speed applications to ensure the reliability and
safety of the application. For this purpose, insulated
bearings or bearing constructions, common mode filters
and suitable cabling and grounding methods (see chapter
6.6) must be used.
14 – ML/EN ABB Motors and Generators | 3GZF500730-47 rev E 06-2015

6.5.1 Elimination of bearing currents

The following methods must be used to avoid harmful
bearing currents in frequency converter driven motors:
Frame size
250 and smaller No actions needed
280 – 315 Insulated non-drive end bearing
355 – 450 Insulated non-drive end bearing
AND
Common mode filter at the converter
For the exact type of bearing insulation, see the motor's
rating plate. Changing the bearing type or insulation
method without ABB's permission is prohibited.

6.6 Cabling, grounding and EMC

To provide proper grounding and to ensure compliance
with any applicable EMC requirements, motors above
30 kW must be cabled using shielded symmetrical cables
and EMC glands, i.e. cable glands providing 360° bond-
ing. Also for smaller motors, symmetrical and shielded
cables are highly recommended. Make the 360° ground-
ing arrangement at all cable entries as described in the
instructions for the glands. Twist the cable shields into
bundles and connect to the nearest ground terminal/
busbar inside the terminal box, converter cabinet, etc.
NOTE!
Proper cable glands providing 360° bonding must be
used at all termination points, e.g. at motor, converter,
possible safety switch, etc.
For motors of frame size IEC 280 and upward, additional
potential equalization between the motor frame and the
driven equipment is needed, unless both are mounted on
a common steel base. In this case, the high frequency
conductivity of the connection provided by the steel base
should be checked by, for example, measuring the poten-
tial difference between the components.
More information about grounding and cabling of variable
speed drives can be found in the manual "Grounding and
cabling of the drive system" (Code: 3AFY 61201998) and
material on fulfilling the EMC requirements can be found in
respective converter manuals.

6.7 Load and speed limitations

6.7.1 General

NOTE!
The maximum speed of the motor must not be
exceeded even if the loadability curves are given up
to 100 Hz.