4
3. Bow Thruster
On the bow thruster side, the target value default settings are received serially by the
operating unit and the relevant proportional-magnet-valves are activated via a servo control
(impulse length control). For return information, the actual value of the propeller angle is
registered analogously and then evaluated.
If target and actual position are too far from each other, the relevant transistor output
(increase or decrease angle) connects through completely. The actual value now tracks the
target value and gets close to it. Within this close-up range, the two proportional solenoid
valves are activated by the impulse durations. Therefore, there should always be a stabile
condition when the system is deactivated (actual value = target value).
The close-up range must be regarded as positive and negative offset around the actual value.
The default value for it corresponds to a certain angle which can be adjusted over 6 DIP-
switches on the circuit board in the terminal box. At this, two criteria have to be considered:
a) The smaller the close-up range can be chosen, the more precisely the actual value is
adjusted to the target value.
b) On the other hand, the value should be chosen high enough to allow balancing (in the
relevant system) of deviations caused by oil leakages, within the range of the impulse length
activation or within the close-up range.
The solenoid valves do not open before a minimum current is reached. The minimum current
is usually 20% of the rated current. This minimum current can be adjusted with a special DIP-
switch.
a) Level 1 = 16% minimum current, which means that the valve is still closed at the start of
the control range.
b) Level 2 = 24% minimum current, which means that the valve is always opened a little bit at
the start of the control range.
The solenoid valves are only activated in connection with enabled start function. The
conditions for enabled start function are as described above.
4. Failure Report
Relay K4 serves for failure report at the bridge side, as well as at the bow thruster side. An
open contact signalises a failure, missing configuration (see Setup) or wire breakage and can
thus be evanluated or indicated correspondingly. Additionally, in case of failure, the start
release is cancelled and the solenoid valves are switched idle.
5. Commissioning
In order to make the system ready for operation, it has to be programmed via the integrated
adjustment software. If programming has not yet been done, the system can not work. In this
case, the failure-relay K4 is activated after switching on of the device and the lamp “ready for
operation” on the bridge flashes in a 5-seconds-cycle; 1 second on, 4 seconds off. Thus, the
user is requested optically to do the programming.