Filters; Filt1; Filt2 - ABB ACSM1 Firmware Manual

Filters

FILT1

(10069)
Illustration
Execution time
Operation
Inputs
Outputs

FILT2

(10070)
Illustration
Execution time
Operation
TLA1 1 msec
I
T1
7.59 µs
The output (O) is the filtered value of the input (I) value and the previous output value
(O ). The FILT1 block acts as 1st order low pass filter.
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Note: Filter time constant (T1) must be selected so that T1/Ts < 32767. If the ratio
exceeds 32767, it is considered as 32767. Ts is the cycle time of the program in ms.
If T1 < Ts, the output value is the input value.
The step response for a single pole low pass filter is:
-t/T1
O (t) = I(t) × (1 - e )
The transfer function for a single pole low pass filter is:
G(s) = 1/ (1 + sT1)
Input (I): REAL
Filter time constant input (T1): DINT, 1 = 1 ms
Output (O): REAL
TLA1 1 msec
X
FRQ
RESET
6.30 µs
The output (Y) is the filtered value of the input (X). The FILT2 block acts as a 2nd order
low pass filter.
When the RESET input value is set to 1, the input is connected to the output without
filtering.
Notes:
• The -3 dB cutoff frequency (FRQ) is limited to its maximum value (16383 Hz).
• The frequency of the input signal must be less than half of sampling frequency (fs) –
any higher frequencies are aliased to the allowable range. The sampling frequency is
defined by the time level of the block; for example, 1 ms corresponds to a sampling
frequency of 1000 Hz.
The following diagrams show the frequency responses for 1, 2, 5 and 10 ms time levels.
The -3 dB cutoff level is represented as the horizontal line at 0.7 gain.
FILT1
67
(1)
O
FILT2
68
(1)
Y
O(67)
Y(68)
Standard function blocks
349