Safe Torque Off (STO)
Instruction handbook b maXX BM4400, BM4600, BM4700
Document No.: 5.12008.07 Baumüller Nürnberg GmbH
334
of 358
C.2
C.2.2.1 Shutdown paths
Shutdown
path A
Safety relay of the BM4000
The function of the safety relay is executed in fail-safe-technology, also named closed-circuit
principle. The safety function is active, if no voltage is applied to the input terminals (102-3/4;
X103-3/4). At power failure the safety function is ensured. 24V must be applied to the particular
terminals (X102-3/4; X103-3/4), in order to deactivate the function.
The present switching state must be responded at the positively driven feedback contact, to
monitor the safety relay externally (X102-1/2; X103-1/2). The positively action contacts are
closed (NC contact), if there is no voltage at the safety relay (STO is active). Also cable break
is recognized as error.
If the voltage at the input terminals of the relay (X102-3/4; X103-3/4) is switched off, the inverter
generates the message „Power unit warning 20: undervoltage safety relay“ or the message
„Power unit error 87: error safety relay“. At an inhibited pulse enable, the warning message
(warning is not saved) is generated. At pulse enable the error message (error message is
saved) is generated. Commissioning or enabling the drive is possible, if there is no error in the
error memory. This error memory can be reset via the digital input X1/1 of the function module
DIO-01. The input X1/1 must be configured accordingly. The starting pulse length at X1/1 must
last at least 5 ms.
Schematic diagram safety relay
NOTE
Th
e starting and the shutdown sequence of the enabling signals and the safety relay
must be considered, in order to assure a faultless operation of the drive.
See ZFigure 111– on page 335.
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