Siemens SINAMICS S120 Function Manual page 415

Speed setpoint when the essential service mode is active
● p3881 specifies the speed setpoint. If you have defined an analog input as setpoint source
using p3881, then for wire breakage, the converter can switch over to setpoint p3882.
● Wire-break monitoring can only take place with a setting as current input at the analog inputs
of the CU310-2 and the TM31. Wire-break monitoring cannot take place with a setting as
voltage input in essential service mode, thus there is no switchover to the alternative
setpoint p3882.
Interaction between bypass and the essential service mode
● If, when activating the essential service mode, bypass operation is active, converter
operation is selected internally in order to ensure that the setpoint is entered via the source
intended for the essential service mode.
● If faults are still present after the number of start attempts parameterized in p1211, then the
converter goes into a fault condition with F07320. In this case, there is an option of switching
over to bypass operation and then directly connecting the motor to the line supply.
Behavior with active speed limitations
In essential service mode, the adjustable speed setpoint of the ESM source observes the
settings of active speed limitations:
● If the set ESM speed is less than the minimum speed, the minimum speed is effective in
essential service mode.
● The settings of the skip frequency bands and maximum speeds are observed.
Automatic switchover to encoderless operation for encoder faults
By automatically pre-assigning parameter p0491 (Motor encoder fault response ENCODER)
with a value of "1", the drive maintains the essential service mode even when the encoder
develops a fault condition.
In addition, setting values "5" or "6"can be used. These setting values are lost after a power
interruption at the Control Unit or the drive restarts. The drive then continues to operate with the
automatic pre-assignment (p0491 = 1).
Pending drive standstill in the essential service mode (ESM)
As a result of the automatic drive switchover to encoderless operation, controlled starting of
the drive after a power interruption can fail, in spite of the fact that the automatic restart
function (AR) is activated. If the drive comes to a standstill, then this can cause severe injury
or death, e.g. for ventilation and smoke extraction systems.
● To avoid the motor coming to a standstill, when the essential service mode (ESM) is
Drive functions
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
8.27 Essential service mode (ESM) for CU310-2 on Blocksize power units
WARNING
activated, switchover the drive to encoderless operation.
Basic functions
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