Burkert 8605 KK Instructions De Service page 28

Illustration 8-4: Out (Output) - Valve set-
tings
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 induc-
tivity 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 unnecessar-
ily 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 fre-
quency but also on the current pulse duty factor τ and the working point.
The valve reacts more sensitively when the working point with average pulse
τ
duty factors (
a pulse duty factor in the limit areas closes to 0 % or close to 100 %.
28 - 8605
Valve set-
~ 50 %) and more slowly when the opening corresponds to