Prerequisites - Siemens SINAMICS S120 Function Manual

In this case, for each encoder overflow, there is a load-side offset of 1/3 of a load
revolution, after 3 encoder overflows, the motor and load zero position coincide
again. The position of the load can no longer be clearly reproduced after one en-
coder overflow.
Note
The ratio stamped on the gearbox type 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 gearbox teeth must be requested from the gearbox
manufacturer.
Notice
The position can only be reproduced if, in the powered-down state, if 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
single-turn encoders.
Note regarding using synchronous motors with a measuring gearbox
Field-oriented control of synchronous motors requires a clear reference between
the pole position and encoder position. This reference must also be carefully main-
tained when using measuring gearboxes: This is the reason that the ratio between
the pole pair number and the encoder revolutions must be an integer multiple w1
(e.g. pole pair number 17, measuring gearbox 4.25, ratio = 4).
4.30.2

Prerequisites

S Absolute encoder
S Firmware release w 2.4
S CU320 with Order No. 6SL3040- ....- 0AA1 and Version C or higher
4.30.3 Integration
The position tracking and measuring gearbox functions are integrated as follows in
the system.
© Siemens AG 2006 All Rights Reserved
SINAMICS S120 Function Manual, 03/2006 Edition
Extended Functions
Position tracking/measuring gearbox
4-303