Siemens SINAMICS S120 Function Manual page 348

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Basic functions

6.21 Position tracking

Tolerance window (p0413)

After switching on, the difference between the stored position and the actual position is

determined and, depending on the result, the following is initiated:

● Difference within the tolerance window

● Difference outside the tolerance window

● The tolerance window is preset to quarter of the encoder range and can be changed.

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.

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 gears: 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).

Commissioning

The position tracking of the measuring gear can be activated in the drive wizard (STARTER)

during the configuration of the drive. During the configuration there is an item for encoder

parameterization. In the encoder dialog, click the "Details" button and activate the checkbox

for position tracking in the displayed dialog.

The parameters p0412 (Measuring gear, rotary absolute encoder, revolutions, virtual) and

p0413 (Measuring gear, position tracking tolerance window) can only be set via the expert

● Absolute encoder

The position is reproduced based on the actual encoder value.

Message F07449 is output.

Function Manual, (FH1), 01/2013, 6SL3097-4AB00-0BP3

Drive functions

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