ABB FSO-21, User Manual

Page: 140 / 540

140 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.
Note: All SLS functions can be active at the same time. Motor speed is limited to the
lowest SLS limit. The lowest trip limit will trip the drive.
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 monitoring limit within monitoring time limit, otherwise
SSE function is activated (see section
SLS with time monitoring and speed above
monitored speed on page 143 ).
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 145 ).
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 FSO monitors and 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 167 ).
SLS reaction when modulation is lost during deceleration ramp
If the user requests the SLS function while the motor speed is above SLS limit, SLS
function will trigger a deceleration ramp to bring motor to SLS speed. 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 have the
motor speed information anymore and the motor coasts to a stop. When it is critical to
receive a safe indication of 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 activate, for example, a safe break. The