DSC - Outputs
Page 22 of 80
1.4 OUTPUTS
1.4.1 Directional Solenoid
Description
The directional solenoid output provides the port and starboard rudder
commands to the 4-way directional solenoid valve on the Hydraulic Power
Unit. The solenoid common signal is a positive 12V or 24V signal that is
connected to the common wire of the 4-way directional valve. The PORT
and STBD command signals provide on-off or proportional commands to
pull the spool of the 4-way valve in either direction. The directional
solenoid outputs are generated either by the DSC or by the backup NFU
system described in section 1.3.6
. The directional solenoid outputs from
the DSC are provided with short circuit protection via Fuse #2 on the DSC.
On-Off commands output full voltage signals that completely shift the
spool of a directional valve giving on-off control of rudder position.
Proportional commands output a pulse width modulated signal that
controls the current flow to a proportional directional valve. Increasing the
current to a proportional valve increases the amount of spool shift and
therefore the flow rate of the hydraulic fluid. The proportional signals allow
the DSC to control the acceleration, deceleration and speed of the rudder
movements. Proportional control provides for smooth quiet operation of
the rudder and reduces wear and tear on the mechanical components of
the steering gear.
The directional solenoid output signals from the DSC are only operational
if the switched power signal is applied to the DSC. Arranging the signals
in this manner will ensure that the directional solenoids are only being
energized when power steering is available. The DSC monitors certain
signals such as rudder feedback in order to shut down the directional
solenoid outputs and hold the present rudder position if a failure in the
signal is detected.
The directional solenoid output signals are routed through the RFU to take
advantage of rudder angle limit switches contained in the RFU. These
limit switches serve to stop the steering gear travel before any mechanical
stops are reached. The adjustable limit switches are cam operated and
directly coupled to the rudder stock through a mechanical linkage.
Specifications
Output Voltage............................. 12 or 24 VDC
Output Format.............................. Common positive
Maximum Output Power .............. 48 W
PWM Frequency .......................... 2 kHz
Connector: ...................................5.08mm pitch screw terminals
Doc No.: MAN01504, 20-02-06 DSC 100 & MCP 100 Manual
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