ABB FSO-12, User Manual

Page: 94 / 388

94 Safety functions
Safely-limited speed (SLS)
The SLS prevents the motor from exceeding user-defined speed limits. The drive
limits the motor speed so that it stays between the SLS speed limits.
If the motor speed is above the user-defined SLS limit when SLS function is
activated, the motor speed is first decelerated to the required speed. You can
configure the SLS function to use either the time monitoring or ramp monitoring
method when the motor speed is decelerated. You can also configure the reaction of
the SLS function in case that the drive modulation is lost during the deceleration
ramp.
Time monitoring
When SLS function is activated at a speed higher than SLS limit, motor starts to
decelerate according to deceleration ramp time defined by drive parameters. The
motor speed must reach SLS limit within monitoring time limit, otherwise SSE
function is activated (see section
SLS with time monitoring and speed above
monitored speed on page 97 ).
Ramp monitoring
When SLS function is activated at a speed higher than SLS limit, motor starts to
decelerate according to deceleration ramp slope defined by SLS SAR1 function. The
motor speed must decelerate within SAR1 minimum and maximum limits, otherwise
STO function is activated (see section
SLS with ramp monitoring and speed above
monitored speed on page 99 ).
Note: If the SLS monitoring must be activated immediately after the SLS request,
regardless of the current speed, time monitoring with a zero time delay (parameter
SLSx.04 ) must be used instead of ramp monitoring.
When the SLS monitoring is active, the drive limits the motor speed, but if the motor
speed still reaches the SLS trip limit, the FSO module activates the SSE function (see
section
SLS trip limit hits on page 121 ).
SLS reaction when modulation is lost during deceleration ramp
SLS function decelerates with a predefined SAR ramp if user has requested SLS
function when motor speed is above the SLS limit. If the drive modulation is lost
during deceleration due to drive error or power failure and FSO is using safe speed
estimate for safety function purposes, then FSO does not know the motor speed and
motor coasts to a stop. When it is critical to react to this situation, FSO parameters
can be set accordingly, starting from FSO rev. H. User can select, whether, in the
case of modulation loss, STO indication is activated. This lets the user to activate, for
example, a safe brake The reaction and delay for the STO indication to activate after
the modulation loss can be set with the FSO parameters.