Siemens SINAMICS S120 Function Manual page 236

Basic functions
6.17 Position tracking
Virtual multiturn encoder (p0412)
With a rotary absolute encoder (p0404.1 = 1) with activated position tracking (p0411.0 = 1),
p0412 can be used to enter a virtual multiturn resolution. This enables you to generate a
virtual multiturn encoder value (r0483) from a singleturn encoder. It must be possible to
display the virtual encoder range via r0483.
NOTICE
If the gear factor is not equal to 1, then p0412 always refers to the motor side. The virtual
resolution, which is required for the motor, is then used here.
For rotary axes with modulo offset, the virtual multiturn resolution (p0412) is preset as p0421
and can be changed.
For linear axes, the virtual multiturn resolution (p0412) is preset as p0421 and extended by 6
bits for multiturn information (max. overflows 31 positive/negative)
If, as a result of extension of the multiturn information, the displayable area of r0483 (2
is exceeded, the fine resolution (p0419) must be reduced accordingly.
Tolerance window (p0413)
After switching on, the difference between the stored position and the actual position is
ascertained and, depending on the result, the following is triggered:
Difference within the tolerance window -> the position is reproduced based on the current
actual encoder value.
Difference outside the tolerance window -> An appropriate message (F7449) is output.
The tolerance window is preset to quarter of the encoder range and can be changed.
NOTICE
The position can only be reproduced if, in the powered-down state, the encoder was moved
through less than half of the range that it can represent. For the standard EQN1325
encoder, this is 2048 revolutions or half a revolution for singleturn encoders.
Note
The ratio stamped on the gear rating plate is often just a rounded-off value (e.g.1:7.34). If, for
a rotary axis, it is not permissible to have any long-term drift, then the actual ratio of the gear
teeth must be requested from the gear manufacturer.
Note regarding using synchronous motors with a measuring gear
Field-oriented control of synchronous motors requires a clear reference between the pole
position and encoder position. This reference must also be carefully maintained when using
measuring geares: This is the reason that the ratio between the pole pair number and the
encoder revolutions must be an integer multiple ≥ 1 (e.g. pole pair number 17, measuring
gear 4.25, ratio = 4).
236
Function Manual, (FH1), 10/2008, 6SL3097-2AB00-0BP5
bit)
32
Drive functions