Siemens SINAMICS S150 NEMA, Operating Instructions Manual

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Functions, monitoring and protective functions
9.3 Drive functions
Enclosed Drives
594
Operating Instructions, 12/2018, A5E36652151A
● A 4x evaluation of the pulse encoder signals allows a minimum speed to be detected
which is a factor of 4 lower than for the 1x evaluation. For incremental encoders with
uneven pulse duty factor of the encoder signals or where the encoder signals are not
precisely offset by 90 °, a 4x evaluation can result in an actual speed value that is
somewhat "unsteady".
● The following formula defines the lowest speed where a distinction can be made to 0:
n
min
= 60 / (x * p0408) [rpm]
with x = 1 or 4 (x times evaluation)
Note
Use the 1x evaluation
The reduction to 1x evaluation is only possible in conjunction with edge zero mark or without
zero mark. Detection with an accuracy of one pulse is no longer possible for zero marks with
"unambiguous range" or distance-coded zero marks.
9.3.25.8 Setting the measuring time to evaluate speed "0"
This function is only necessary for slow-speed drives (up to 40 rpm rated speed) in order to
be able to correctly output actual speeds close to 0. For a stationary drive, this prevents that
the I component of the speed controller slowly increases and the drive unnecessarily
establishes a torque.
Commissioning
The desired measuring time is entered in parameter p0453. A speed actual value of "0" is
output, if, within this time, no pulses are detected from the A/B track.
9.3.25.9 Sliding averaging of the speed actual value
For slow-speed drives (< 40 rpm), when using standard encoders with a pulse number of
1024, a problem is encountered due to the fact that the same number of encoder pulses is
not available for every current controller clock cycle (for p0430.20 = 1: Speed calculation
without extrapolation, "Incremental difference"). The different number of encoder pulses
means that the speed actual value display jumps, although the encoder itself is rotating at a
constant speed.
Commissioning
"Sliding averaging" is activated with p0430.20 = 0 (edge time measurement).
The number of current controller clock cycles must be entered in parameter p4685, from
which the average value is generated for calculating the speed. The averaging means that
individual incorrect pulses, depending on the number of specified clock cycles, are
smoothed.