hello guys 

what is the difference between controlling OFF1 and OFF2 and using safety function ( STO and SS1 ) ?

Hi, SS1 or STO safety functions ALWAYS take priority over any other running conditions.

Most Siemens drive manuals explain the functions of the OFF categories

OFF1 accel/decel drive based on ramp

OFF2 disconnect power i.e. coast to standstill

OFF3 ramp down based on the separate OFF3 ramp time

SS1 is also a ramp based deceleration safety function, and STO is the power disconnection (i.e. no torque hence the STO acronym: Safe Torque Off).

STO usually follows an SS1 although, this is not always the case and an STO can be applied instantly but this means that any kinetic energy will still be present.

Regards,

Graeme