Figure 16:
Out (output) - Valve setting
ValV (ValVe) - setting Of the ValVe type
CauTion!
danger from the selection of the wrong valve type!
The valve can be damaged if the wrong valve type is selected.
•
Pay attention to the choice of the right valve type.
The Control Electronics, Type 8605, can be used for the whole range of Bürkert proportional valves. Depending on
the nominal sizes and fluidic performance data, the individual valve types contain solenoid coils with very different
sizes, winding data and dynamic properties (defined by the inductivity and Ohmic resistance).
The ability to react to a PWM voltage signal with a small dither movement and hence to give the valve a particularly
good response depends to a very great extent on the dynamic characteristic of the coil.
As a general rule of thumb it can be said that small coils with low magnetic force still react well even to higher
frequencies. At low frequencies, they even generate excessively large movement amplitudes and an unnecessarily
high noise level. Large coils with high magnetic force still generate dither movements only at low frequencies and
thus ensure sliding friction states.
The reaction of a valve to a PWM signal is dependent not only on its frequency but also on the current pulse duty
factor
and the working point.
τ
The valve reacts more sensitively when the working point with average pulse duty factors (τ ~ 50 %) and more slowly
when the opening corresponds to a pulse duty factor in the limit areas close to 0 % or close to 100 %. In order to
compensate this dependence, control is effected with a PWM frequency that is dependent on the pulse duty factor
whose curve follows a triangular function (see Figure 17: PWM frequency / pulse duty factor). Here the frequency
is lowest at the limit points (0 %, 100 %), and highest at τ = 60 %.
24
english
Type 8605
Configuration