Low Voltage Motors In Variable Speed Operation; Introduction; Winding Insulation; Phase To Phase Voltages - ABB Low Voltage Motors Manuel D'installation, D'exploitation Et De Maintenance

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
ABB/Manual for Low Voltage Motors 01-2009
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 of the
N
converter
U ≤ 500 V
N
U ≤ 600 V
N
U ≤ 690 V
N
U ≤ 690 V
N
AND
cable length > 150 m
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.

5.4 Bearing currents

Insulated bearings or bearing constructions, common
mode filters and suitable cabling and grounding methods
must be used according to the following instructions:
Winding insulation and
filters required
ABB Standard insulation
ABB Standard insulation
+ dU/dt filters
OR
ABB Special insulation
(variant code 405)
ABB Special insulation
(variant code 405)
AND
dU/dt-filters at converter
output
ABB Special insulation
(variant code 405)
EN-11