STO (Safe Torque Off)
The status of the STO activity is included in bit 15 of the CiA status word (0x6041 (P780.00)).
This status information is required since the activation of STO causes all integral control parts to be deleted.
In case of hoists, for instance, the inverter would be sagging without any corrective measures after completing STO.
In order to prevent this unwanted state, the control has to be preloaded with a starting value after completing STO:
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In case of a control type with encoder, the integral-action component of the speed controller must be preloaded.
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In case of V/f characteristic control for asynchronous motor (VFC closed loop), the slip frequency must be preloaded.
If STO is inhibited, a changeover to the "Ready to switch on" device state takes place and a warning is output.