Functions
8.18 Fail-safe functions
Control Units CU240S
8-102 Operating Instructions, 11/2006, A5E00766042B AA
Forced dynamisation
The forced dynamisation process delays the switch-on process after a Safe Torque Off
(STO), but it ensures that all the fail-safe features of the inverter are functioning correctly.
However, should this delay after a STO be unacceptable for the user application, it can be
disabled by setting parameters P9601 = P9801 = 0.
The forced dynamisation process is automatically initiated by the following events:
● On power-up of the inverter.
● When the Latched Safe Torque Off (LSTO) function is deactivated.
● When the Safe Torque Off (STO) is left (if P9601 = P9801 = 2).
● When Safe Stop 1 (SS1) is left after STO was reached (if P9601 = P9801 = 2).
● When commissioning of fail-safe functions is left.
Note
When carrying-out the forced dynamisation, the shutdown paths of the motor brake are
also tested. This results a brief opening command (2 ms to 30 ms) in the motor brake.
The mechanical part of the brake generally requires longer than 30 ms to open. This
means that this dynamic operation generally has no influence on the motor shaft itself.
Process dynamisation
The process dynamisation will be performed after STO initialisation or SS1 end only if P9601
= P9801 = 2.
The testing includes both shutdown paths, but does not perform a processor self-test or a
test of the Safe Brake Control.
Warning
Dynamisation of the shutdown paths
For safety reasons, it is necessary to initiate a safe torque off as a test at intervals of
maximal 8760 hours (one year) in order to check its operability. Thus, 8760 hours after the
last activation of the safe torque off the converter sets a status bit that specifies this
requirement.
The process control must then initiate the safe torque off at the next opportunity, for
example, when the drive has in any case a short phase with zero speed. If the converter
returns the "safe torque off initiated" status signal, the torque off can be released again. The
setting and clearing of the status bit and the dynamisation must be logged as process data
by the higher-level control.
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