Siemens Sinamics S110 Function Manual page 153

To accept a high load torque even in the open-loop controlled range, the motor current can
be increased via p1612. To do so, the drive torque (e.g. friction torque) must be known or
estimated. An additional reserve of approx. 20% should also be added. In synchronous
motors, the torque is converted to the current via the motor torque constant (p0316). In the
lower speed range, the required current cannot be measured directly on the Power Module.
The default setting is 50% (synchronous motor) or 80% (induction motor) of the motor rated
current (p0305). When parameterizing the motor current (p1612), you must take into account
the thermal motor load.
Note
Operation without an encoder is not permitted for vertical axes or similar. Operation without
an encoder is not suitable for a higher-level closed-loop position control either.
The start behavior of synchronous motors from standstill can be improved further by
parameterizing the pole position identification (p1982 = 1).
Behavior once pulses have been canceled
Once the pulses have been canceled in operation without an encoder, the current actual
speed value of the motor can no longer be calculated. Once the pulses are enabled again,
the system must search for the actual speed value.
p1400.11 can be used to parameterize whether the search is to begin with the speed
setpoint (p1400.11 = 1) or with speed = 0.0 (p1400.11 = 0). Under normal circumstances,
p1400.11 = 0 because the motor is usually started from standstill. If the motor is rotating
faster than the changeover speed p1755 when the pulses are enabled, p1400.11 = 1 must
be set.
If the motor is rotating and the start value for the search is that of the setpoint (p1400.11 =
1), the speed setpoint must be in the same direction as the actual speed before the pulses
can be enabled. A large discrepancy between the actual and setpoint speed can cause a
malfunction.
Once the pulses have been canceled, no information about the motor speed is available.
The computed actual speed value is then set to zero, which means that all actual speed
value messages and output signals are irrelevant.
Switchover between closed-loop/open-loop operation and operation with/without encoder
Operation without an encoder is activated via parameter setting p1300 = 20. If p1300 = 20 or
p1404 = 0, operation without an encoder is active across the entire speed range. If the
speed value is less than the changeover speed p1755, the motor is operated in accordance
with the current/frequency.
During operation with an encoder, a switchover can be made to operation without an
encoder when the speed threshold p1404 is exceeded. If p1404 > 0 and p1404 < p1755, a
switchover to operation without an encoder is not made until the speed exceeds p1755.
Function Manual
Function Manual, 01/2011, 6SL3097-4AB10-0BP3
WARNING
Drive functions
7.1 Servo control
151