Siemens SINAMICS G130 Engineering Manual page 275

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The special versions of motors for SIMOVERT A (motors in 1LA6 range of frame size 315L or higher,
motors in 1LA8 range with letters "QS" or "QT" in the order number, and motors in 1LA1 range in general)
are designed to be low-leakage, while converters like SINAMICS, which are PWM converters with voltage-
source DC-link, require high-leakage motors. If low-leakage motors are operated on a SINAMICS
converter, a higher current ripple with significantly higher current peaks can develop in the motor current.
On the one hand, this causes a higher temperature rise in the motor as the result of increased stray
losses. On the other, it poses the risk of overcurrent tripping in response to dynamic load peaks. For this
reason, very careful consideration should be given to certain factors before a SIMOVERT A converter,
which is operating with a special motor for SIMOVERT A, is replaced by a SINAMICS converter. A
replacement should only be considered as a serious option if the motor can provide thermal reserves in
the order of magnitude of about 5 % to 10 % and if the drive will be operated without pronounced load
peaks. In contrast, if the existing motors are from the 1LA6 series with frame size 315M or smaller, or
basic models of motors in the 1LA8 range, the current ripple and current peaks in the motor current do not
reach critical values.
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Motors in the 1LA1 range can be 3-phase (for 6-pulse operation) or 6-phase (for 12-pulse operation). The
6-phase variant always has a phase displacement angle of 30 °el. between the two winding systems.
6-phase motors of this type cannot be operated on SINAMICS units (including parallel converters) on
which firmware version 4.5 or lower is installed. With firmware version 4.6 and higher, winding systems
which are out of phase by 30° are basically possible if certain boundary conditions are fulfilled. Further
information is available on request.
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SIMOVERT A converters are generally designed for 4Q operation, i.e. without modification or upgrading.
When SINAMICS is chosen as a replacement converter, it is therefore necessary to clarify whether the
converter is required to operate in regenerative mode for the application in question so that the correct
converter for either 1Q or 4Q mode is selected.
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As a result of their pulse-width modulation operating principle, PWM converters like SINAMICS cause an
increase in motor noise as compared to the SIMOVERT A converters. For this reason, an increase in
motor noise of between about 5 dB(A) – 7 dB(A) must be expected if a SIMOVERT A converter is
replaced by a SINAMICS converter.
It is also important to note the potential problems affecting the motors:
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Voltage stress on the motor winding
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Bearing currents in the motor bearings.
Solutions to counter these problems are available. For example, motor reactors or motor filters can be installed at the
SINAMICS converter output, or the motor can be retrofitted with an insulated bearing in an approved service
workshop.
1. Measures recommended when replacing SIMOVERT A converters for a line supply voltage of 500 V
1.1 Operation with 1LA6 and 1LA8 motors:
·
Use a motor reactor on the SINAMICS converter to reduce the voltage rate-of-rise dv/dt and retrofit an
insulated bearing to the non-drive end of the motor
or
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Use a dv/dt filter plus VPL or a dv/dt filter compact plus VPL on the SINAMICS converter, but do not
modify the motor
1.2 Operation with 1LA1 motors with a 3-phase winding (for 6-pulse operation):
·
No measures required
2. Measures recommended when replacing SIMOVERT A converters for a line supply voltage of 690 V
2.1 Operation with 1LA6 and 1LA8 motors:
·
Use a dv/dt filter plus VPL or a dv/dt filter compact plus VPL on the SINAMICS converter, but do not
modify the motor
2.2 Operation with 1LA1 motors with a 3-phase winding (for 6-pulse operation):
·
No measures required
1)
Notice! If the motor is retrofitted with an insulated non-drive end bearing and also has a speed encoder, the
encoder must also be insulated or replaced by an encoder with insulated bearings.
General Engineering Information for SINAMICS
1)
SINAMICS Engineering Manual – November 2015
Engineering Information
275/528
Ó Siemens AG