ABB FSO-21 - Page 189

Safety functions 189
Step Description
1 The SDI positive request is received (for example, from the I/O). The motor rotates into
the forbidden direction (in this case, negative). The drive starts to decelerate the motor
speed to zero speed. The drive (parameter 23.13 or 23.15) defines the deceleration
ramp. The FSO module starts a counter for time A. The SDI active indication is off.
2 The motor speed reaches zero and the motor stops. The FSO starts the SDI monitoring
according to the SDI tolerance limit degree (not shown in this figure, see section SDI
with correct rotation direction on page 186). The SDI active indication goes on.
2b The FSO starts the SDI monitoring at the latest here, that is, after the SDI delay (A) has
elapsed.
Note: If the rotation direction of the motor is not correct after the SDI delay (A) has
elapsed, the FSO module activates the SDI monitoring. If the motor rotates to the
forbidden direction more that the SDI tolerance limit degree (parameter SDI.14, not
shown in this figure) allows, the FSO activates the SSE function and the motor coasts
to a stop (in this case the SSE function has been configured as “Immediate STO”). See
section SDI trip limit hits on page 192.
3 The user gives a new speed reference. The motor starts to rotate into the correct
(positive) direction.
3b Zero speed limit (B) reached. If the SSE function was activated at 2b, the STO
acknowledgement becomes allowed and the FSO starts the SDI monitoring.
4 The SDI request is removed and the FSO stops the SDI monitoring. The SDI function is
acknowledged (automatic SDI acknowledgement) and the SDI active indication goes
off.