Operation Without An Encoder - Siemens Sinamics S110 Function Manual

Drive functions
7.1 Servo control
7.1.11

Operation without an encoder

NOTICE
The operation of synchronous motors without an encoder must be verified in a test
application. Stable operation in this mode cannot be guaranteed for every application.
Therefore, the user will be solely responsible for the use of this operating mode.
Description
This allows operation without an encoder and mixed operation (with/without encoder).
Encoderless operation with the motor model allows a higher dynamic response and greater
stability than a standard drive with V/f control. Compared with a drive with an encoder,
however, speed accuracy is lower and the dynamic response and smooth running features
deteriorate.
Since the dynamic response in operation without an encoder is lower than in operation with
an encoder, accelerating torque pre-control is implemented to improve the control dynamic
performance. It controls, knowing the drive torque, and taking into account the existing
torque and current limits as well as the load moment of inertia (motor moment of inertia:
p0341*p0342 + load torque: p1498) the required torque for a demanded speed dynamic
performance optimized from a time perspective.
Note
If the motor is operated with and without an encoder (e.g. p0491 not 0 or p1404 < p1082),
the maximum current during operation without an encoder can be reduced via p0642
(reference value is p0640) in order to minimize interfering, saturation-related motor data
changes during operation without an encoder.
A torque smoothing time can be parameterized via p1517 for the torque pre-control. The
speed controller needs to be optimized for operation without an encoder due to the lower
dynamic response. This can be carried out via p1470 (P gain) and p1472 (integral time).
In the low-speed range, the actual speed value, the orientation, and the actual flux can no
longer be calculated during operation without an encoder due to the accuracy of the
measured values and the parameter sensitivity of the process. For this reason, an open-loop
current/frequency control is selected. The switchover threshold is parameterized via p1755
and the hysteresis via p1756.
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Function Manual, 01/2011, 6SL3097-4AB10-0BP3
Function Manual