5. Low voltage motors in variable speed operation
5.1 Introduction
This part of the manual provides additional instructions for
motors used in frequency converter supply. Instructions
provided in this and respective manuals of selected
frequency converter must be followed to ensure safety and
availability of the motor.
Additional information may be required by ABB to decide
on the suitability for some machine types used in special
applications or with special design modifications.
5.2 Winding insulation
Variable speed drives cause higher voltage stresses than
the sinusoidal supply on the winding of the motor and
therefore the winding insulation of the motor as well as
the filter at the converter output must be dimensioned
according following instructions.
5.2.1 Phase to phase voltages
The maximum allowed phase to phase voltage peaks at
the motor terminal as a function of the rise time of the pulse
can be seen in Figure 1.
The highest curve “ABB Special Insulation” applies to
motors with a special winding insulation for frequency
converter supply, variant code 405.
The “ABB Standard Insulation” applies to all other motors
covered by this manual.
5.2.2 Phase to ground voltages
The allowed phase to ground voltage peaks at motor
terminals are:
Standard Insulation 1300 V peak
Special Insulation 1800 V peak
5.2.3 Selection of winding insulation for
ACS800 and ACS550 converters
In the case of ABB ACS800-series and ACS550-series
single drives with a diode supply unit (uncontrolled DC
voltage), the selection of winding insulation and filters can
be made according to table below:
Nominal supply
voltage U
N
of the
converter
Winding insulation and
filters required
U
N
≤ 500 V
ABB Standard insulation
U
N
≤ 600 V
ABB Standard insulation
+ dU/dt filters
OR
ABB Special insulation
(variant code 405)
U
N
≤ 690 V
ABB Special insulation
(variant code 405)
AND
dU/dt-filters at converter
output
U
N
≤ 690 V
AND
cable length > 150 m
ABB Special insulation
(variant code 405)
For more information on resistor braking and converters
with controlled supply units, please contact ABB.
5.2.4 Selection of winding insulation
with all other converters
The voltage stresses must be limited below accepted limits.
Please contact the system supplier to ensure the safety of
the application. The influence of possible filters must be
taken into account while dimensioning the motor.
5.3 Thermal protection
Most of the motors covered by this manual are equipped
with PTC thermistors in the stator windings. It is
recommended to connect those to the frequency converter
by appropriate means. See also chapter 3.8.2.
Low voltage motor manual 01-2009
| ABB Motors and Generators
EN-11
