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POS-123-P-PFN
5.6.2
DAMPL (Dither amplitude)
5.6.3
DFREQ (Dither frequency)
Command
Parameter
Unit
Group
DFREQ
X
DAMPL
X
x= 60… 400
x= 0… 3000
Hz
0.01 %
POWERSTAGE
The dither signal
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can be defined with these commands. Different amplitudes or frequencies may be required
depending on the valve. The dither amplitude is defined in % (peak to peak value) of the nominal output cur-
rent
6
. The dither frequency is defined in Hz. Depending on the internal calculations, the frequency is adjustable
in steps only
7
.
CAUTION: The PPWM and IPWM parameters influence the effect of the dither setting. These
parameters should not be changed after the dither has been optimized.
CAUTION: If the PWM frequency is less than 500 Hz, the dither amplitude DAMPL should be
set to zero.
5.6.4
PWM (PWM Frequency)
Command
Parameter
Unit
Group
PWM
X
x= 60
… 2
941
Hz
POWERSTAGE
The frequency can be changed in defined steps (60 Hz, 70 Hz, 80 Hz, 90 Hz, 100 Hz, 110 Hz, 120 Hz, 130
Hz, 150 Hz, 199 Hz, 230 Hz, 280 Hz, 336 Hz, 405 Hz, 511 Hz, 1069 Hz, 1470 Hz, 1960 Hz, 2352 Hz, 2941
Hz). The optimum frequency depends on the valve.
Attention: The PPWM and IPWM parameters should be adapted when using low PWM frequencies
because of the longer dead times which forces a reduced stability of the closed loop control. This set-
tings are done automatically if ACC is set to ON.
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The dither is a square wave signal which is superimposed on the current set point and is defined by the amplitude and
frequency: the dither frequency and the PWM frequency.
The dither frequency should not be confused with the PWM fre-
quency
.
In some documentations the PWM frequency is described as a dither. This can be recognized by the lack of the
dither amplitude.
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The dither amplitude is a command signal. Derivations between the commanded amplitude and the real amplitude are
possible, depending on the dynamic of the solenoid.
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The lower the dither frequency, the smaller the steps. Therefore no practical problems are expected.
