Bearing Currents; Motor Protection - Siemens SINAMICS G130 Engineering Manual

11.9

Bearing currents

The fast-switching IGBTs in the inverter cause steep voltage edges which generate bearing currents in the motor.
Under unfavorable conditions, these currents can reach relatively high values, cause damage to the bearing and
therefore reduce its lifetime.
To prevent damage by bearing currents, it is recommended that converter-fed motors above a certain shaft height
are equipped with an insulated bearing at the non-drive end (NDE).
Insulated bearings at the non-drive end are available as an option for SIMOTICS SD standard motors of shaft height
225 and larger and this option is strongly recommended if these motors are to be fed by converters.
All SIMOTICS TN series N-compact trans-standard motors of types 1LA8, 1PQ8 and 1LL8 which are designed for
converter-fed operation ("P" in the 9th position of the order number, e.g. 1LA8315-2PM80) are equipped as standard
with insulated non-drive end bearings.
The converter-optimized motors from the SIMOTICS FD range are equipped as standard with an insulated NDE
bearing.
The SIMOTICS TN series H-compact and H-compact PLUS trans-standard motors for converter-fed operation are
equipped as standard with an insulated non-drive end bearing.
SIMOTICS M series 1PL6, 1PH7 and 1PH8 compact asynchronous motors in frame size 180 and larger are
optionally available with insulated non-drive end bearings (order code L27). These compact asynchronous motors are
equipped as standard with insulated non-drive end bearings in frame size 225 and larger.
In systems with speed encoders, it must be ensured that the encoder is not installed in such a way that it bridges the
bearing insulation, i.e. the encoder mounting must be insulated or an encoder with insulated bearings must be used.
For further information, please refer to the section "Bearing currents caused by steep voltage edges on the motor" of
the chapter "Fundamental Principles and System Description".
11.10

Motor protection

Motors can be protected against thermal overloading by the I
firmware. This mechanism prevents motors from operating continuously at excessive motor currents and represents a
simple method of thermal motor protection which can operate without external components.
More precise motor protection, which also takes into account the influence of the ambient temperature, is possible by
temperature detection using KTY84 or PT1000 temperature sensors or PTC thermistors in the motor winding.
Depending on the motor series, the following must be stated in the order for a KTY84 sensor:
- 1LE1 motors:
- 1LG6, 1LA8/1PQ8 motors:
- 1PL6, 1PH7 and 1PH8 motors:
Depending on the motor series, the following must be stated in the order for PTC temperature sensors:
- 1LE1 motors with 3 temperature sensors for tripping:
- 1LE1 motors with 6 temperature sensors for warning and tripping:
- 1LG6 motors with 3 temperature sensors for tripping:
- 1LG6 motors with 6 temperature sensors for warning and tripping:
- 1LA8/1PQ8 motors with 3 temperature sensors for tripping:
- 1LA8/1PQ8 motors with 6 temperature sensors (warning and tripping): Motor option A12
For thermal monitoring of the windings of 1LG6, 1LE1 and 1LA8/1PQ8 motors, PT100 temperature sensors
(resistance thermometers) are available as an alternative.
Depending on the motor series, the following must be stated in the order for PT100 temperature sensors:
- 1LE1 motors with 3 temperature sensors:
- 1LE1 motors with 6 temperature sensors:
- 1LG6 motors with 3 temperature sensors:
- 1LG6 and 1LA8/1PQ8 motors with 6 temperature sensors: Motor option A61
On SINAMICS G130 built-in units, the KTY84 or PT1000 temperature sensors and the PTC thermistors are
connected to terminal –X41 of the Power Module for evaluation. On SINAMICS G150 and S150 cabinet units, the
sensors can be connected to the optionally available customer terminal block (TM31 Terminal Module / option G60).
If the converter or inverter is equipped with an SMC30 Sensor Module for connection of a pulse encoder, the
temperature sensors can also be connected to the Sensor Module.
The TM150 Terminal Module can also be used to evaluate any of the temperature sensors specified above (KTY84,
PT1000, PT100 and PTC). This has been available as a SINAMICS system component with integrated DRIVE-CLiQ
connection since introduction of firmware version 4.5 and can be ordered as option G51 – G54 for the converter
cabinet units, see also section "Options G51 – G54 (TM150 Terminal Module)" in chapter "Description of Options for
Cabinet Units".
2
t monitoring function integrated in the SINAMICS
Letter F in the 15th position of the order number
Motor option A23
Installed as standard
Letter H in the 15th position of the order number
Letter J in the 15th position of the order number
Motor option A60
SINAMICS Engineering Manual – November 2015
Engineering Information
Letter B in the 15th position of the order no.
Letter C in the 15th position of the order no.
Motor option A11
Motor option A12
Installed as standard
Ó Siemens AG
Motors
527/528