STO FUNCTION
APPLICATION MANUAL
SINUS PENTA
PENTA MARINE
IRIS BLUE
11/
27
The circuit operation is straightforward, and similar to the previous example.
In both cases, the ENABLE-A and ENABLE-B command circuits shall be carried out with care on the
cables layout, avoiding that possible damage to cable insulation could result in unwanted circuit excitation.
In particular, shielded cables are recommended if the signals shall be routed for long distances and cables
might be damaged.
In this case,
the shield shall be connected to the 0Vdc circuit. The ‘0’ terminal beside the ‘S’ terminal and
terminal “22” shall be used for the connection of the cable shield to the 0Vdc/CMD circuit.
If the shielded cable is severed, the short circuit between the shield and the internal conductor will de-
energize the affected ENABLE circuit, guaranteeing the activation of the STO function.
WARNING
The Safe Torque Off function does not cut off the mains voltage and auxiliary
circuits from the drive. Therefore, maintenance work on electrical parts of the
drive or the motor can only be carried out after isolating the drive system from
the mains supply.
NOTE
The Safe Torque Off function can be used for stopping the drive in emergency
stop situations. In normal operating mode, it is recommended not to stop the
drive by using the Safe Torque Off function. If a running drive is stopped by
using the Safe Torque Off function, the drive will trip and perform a coast to
stop. If this is not acceptable, e.g. causes danger, the drive and machinery
must be stopped using the appropriate stopping mode instead of adopting the
STO function.
NOTE
Note concerning permanent magnet motor drives in case of multiple
IGBT power semiconductor failure:
Due to the possible DC output voltage present for certain multiple IGBT
failures, in spite of the activation of the Safe Torque Off function, the drive
system can produce an alignment torque which maximally rotates the motor
shaft by 180/p degrees (p is the pole pair number).
NOTE
It is recommended to route two separate conductors for the ENABLE-A and
ENABLE-B input signals to the drive. This will avoid common failures that can
result in an unwanted deactivation of the STO function.
