ABB FSO-12, Руководство пользователя

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Safety information and considerations 33
During the deceleration, when the motor torque is -100%, the motor slip is again in its
maximum value. Because of the torque direction, FSO speed estimates are below the
actual motor speed (amount of the slip). After the FSO safe speed estimates reach 0
rpm, they begin to show reverse (negative) motor speed due to the negative motor
slip. The FSO module starts to compare the safe speed estimation to the negative
SLS trip limit value. Because the trip limit is much lower than the estimated speed,
there will be no fault trip.
Transient mute time feature
WARNING! The transient mute time increases the response time of the safety
system. This must be considered in the design.
FSO module has a transient mute time feature that can be used to mute the
monitoring limits for a short period so that unnecessary trips can be eliminated. This
can be especially useful with the safe speed estimate due to its inaccurate nature.
In rapid speed change situations, for example in acceleration or direction changes,
the safe speed estimation can reach the safety function trip limit for a short period of
time. These situations can cause an unnecessary trips. The transient mute time
feature can mute the monitoring for short pre-defined periods and prevent
unnecessary trips.
Transient mute time means that for example in case of a limit hit, the FSO safety
function reacts only after the transient mute time has passed if the speed is still above
the trip limit. However, the transient mute time should be set as short as possible.
Transient spikes in the speed signal ( 200.01 FSO speed ch1 , 200.02 FSO speed
ch2 ) should be verified with the Drive composer pro tool. You must test all transient
situations within the whole speed range of the application without any safety functions
active.
Using the transient mute time with the safe speed estimation
When there are spurious transients in safe speed estimate, you can use the transient
mute time in the safety functions. The transient mute time can be set to cover the
transient situation with the parameter:
• FSOGEN.31 Transient mute time
The setting covers limit hits, monitoring start and zero speed limits