Safe Speed Monitor (Ssm) - Mitsubishi Electric MELSEC Q Series Programming Manual

2 SAFETY OBSERVATION FUNCTION

2.5 Safe Speed Monitor (SSM)

Motor speed
(SLS monitoring speed)
Specified speed
(Safety speed)
Shut-off signal
(Y A)
SSM signal output
The safe speed monitor signal (SSM signal) is turned ON if both the command speed
and feedback speed are the safety speed or lower during speed monitoring. The
output signals of safety signal module are used as SSM signal.
If the command speed or feedback speed exceeds the safety speed, SSM signal
output is turned ON to OFF regardless of the speed monitoring error detection time.
If both command speed and feedback speed become smaller than the hysteresis width
from safety speed, SSM signal output is turned OFF to ON again. The SSM signal
chattering can be prevented by setting hysteresis width when the motor speed
fluctuates around the safety speed.
Set the device number of SSM signal output and hysteresis width by parameter.
V
SSM signal output is constantly updated regardless of the safety observation error
while the speed monitoring enabled signal is ON. SSM output is OFF when the speed
monitoring enabled signal is OFF.
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Hysteresis width
t
If the speed continues to exceed
the safety speed, the error occurs.