184 Safety functions
SSM with a safe speed estimate
This section describes situations when an encoder is not used and the drive stops
modulating when the SSM monitoring is on.
Case A: This applies when the drive stops modulating after the SSM monitoring limit
has been reached.
A SSM1 limit positive (parameter SSMx.13)
B SSM1 limit negative (parameter SSMx.12)
C Time to zero speed (parameter STO.14): When the drive stops modulating, SSM1
indication goes on after this delay.
SSM limits (A and B)
Step Description
1 The SSM1 request is received (for example, from the I/O) and the FSO starts the
SSM1 monitoring. The motor speed is between the SSM1 limit positive (A) and SSM1
limit positive (B). The SSM1 indication goes on.
2 The drive stops modulating and the FSO starts a counter for time C. The motor speed
starts to decelerate. While the drive is not modulating, the state of the FSO outputs is
based on the latest speed information from modulation.
3a The drive starts to modulate again and the FSO receives the actual motor speed again.
The motor speed is between the SSM1 limit positive (A) and SSM1 limit positive (B),
and the SSM1 indication stays on.
3b Time C has elapsed, but the drive is still not modulating. The FSO assumes that the
motor has stopped. The motor speed is still between the SSM1 limit positive (A) and
SSM1 limit positive (B), and the SSM1 indication stays on.
4 SSM1 request is removed and the FSO stops the SSM1 monitoring. The SSM1
indication goes off.
SSM1 state &
indication
SSM1 request
Motor speed
Time
A
1
B
2 3a
4
3b
STO.14
C
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