Siemens Simovert Masterdrives Compendium page 9

Definitions and Warnings
Recidual risks upon operation of synchronous motors (brushless DC)
DANGER
4
Using fault analysis, the machinery construction OEM is in the position
to determine the residual risk at his machine regarding the control.
The following residual risks are known:
♦ An acceleration of the motor speed or axis motion can be caused by
the following faults:
− Faults in the absolute measuring systems (CD track or
EnDat/SSI absolute encoder).
− Cyclically interchanged phases of the motor connections (V-W-U
instead of U-V-W).
− Interchanged control sense (e.g. A/B track confused, opposing
attachment of measuring system, etc.).
− Electric faults (defective components, etc.).
♦ If two power transitions in the inverter are simultaneously destroyed,
depending on the motor pole number, this can cause brief axis
movement.
− Example: Synchronous motor:
For a 6–pole synchronous motor, the axis can move by a
maximum of 30 degrees.
With a ballscrew that is directly driven (e.g. 20 mm per
revolution) this corresponds to a maximum linear motion of
approximately 1.6 mm.
− Example, synchronous linear motor:
For a synchronous linear motor, the movement can be a
maximum of one pole width.
For a linear motor, this corresponds to the following distances:
 1FN3
-...
♦ For a 1–encoder system, encoder faults are detected by various HW
and SW monitoring functions. It is not permissible that these
monitoring functions are deactivated and they must be
parameterized carefully.
♦ Stop function Category 0 according to EN 60204-1 means that the
spindle/axes are not braked. Depending on the kinetic energy
involved, they coast down for a long time.
This has to be integrated in the logic of the protection concept (e.g.
with a logic operation with the signal n < nx).
♦ When a limit value is violated, higher speeds than have been set
can briefly occur or the specified position can be exceeded to some
degree from between the error being detected and the system
responding. This depends on the dynamic response of the drive and
the parameter settings.
♦ Parameterization and programming errors made by the machinery
construction OEM cannot be identified. The required level of safety
can only be assured by thorough and careful acceptance testing.
20 mm
6SE7087-6QX70 (Version AN)
Compendium Motion Control
08.2012
Siemens AG
SIMOVERT MASTERDRIVES