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FAULT
ENABLE is active; the
READY LED is active; no
current to the solenoid (no
pressure-build-up).
ENABLE is active, the
READY LED is active and
the pressure is instable.
ENABLE and START
(PIN 6) are active, READY
LED is ON, the pressure
control works, but the pres-
sure is not equal to the
command input.
4
Maybe you have to adjust / optimize the solenoid control loop (P and I).
5
In most applications (particularly pressure-actuated pumps) with pressure valves a lower PWM-frequency is the better
solution.
Page 33 of 34
CAUSE / SOLUTION
No pressure command input is available or the parameterization is incorrect.
With the WPC-tool you can check if a command input is available. If not, you
should check the wiring and/or the command set-point (in the PLC for example).
If the command input is correct, you have to check the valve control parameter.
If the current is set too low (parameter CURRENT), the output current and the
expected pressure are too low.
Wrong configured pressure sensor. If the input-scaling is set to voltage (V) and
the pressure sensor supplies a current signal (4... 20mA), the measured pres-
sure value is always high. The output signal to the valve is therefore low.
The pressure valve is controlled correctly (the output is going up to the nominal
current). In this case you may have a hydraulic problem or you are using free-
wheeling-diodes in the solenoid plug. Please remove the free-wheeling-diodes
to allow a correct current measurement.
In many cases you may have a hydraulic problem.
Electrical problems may be:
Electrical noise at the wire of the power supply.
Very long solenoid wiring (> 40 m), disturbance in the current control loop
Instable current control loop. The adjustments of the PWM-frequency and the
dither (frequency and amplitude) have to be checked carefully. Good experi-
ences are made with:
a.
PWM-frequency = 2600 Hz (higher frequency), the dither has to be aligned
to the valve (amplitude and frequency).
PWM-frequency = 100... 400 Hz (lower frequency), the dither amplitude is
b.
set to 0 % (disabled)
The system works generally, but wrong control loop settings or wrong adjustment of
the input signals cause control errors.
1.
The feedback value is proportional to the command input value, but the output
values are too high or too low. In this case the scaling of one input is wrong.
a. The scaling of the valve is affected by the adjustment of the output current
and the parameter MAX.
E.g. the valve has a nominal range of 320 bar and the working pressure
range is 240 bar, the parameter MAX has to be decreased.
b. AIN-command for sensor scaling. The working range of the sensor is 400
bar and the control range should be 240 bar following changes have to be
done:
AIN:X 400 240 0 V.
c. For a sensor with current output you have to consider the 4... 20 mA scaling:
AIN:X 1250 1000 2000 C
d. 4... 20 mA plus sensor scaling:
AIN:X 1250 600 2000 C (600 = 1000 * 240 bar / 400 bar).
PQP-171-P
5
.
4
.
05.06.2020
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