rolls-royce User Manual Rolls-Royce Helicon X3 P&T Control System

(+/- 180 degrees).

4.2.1 Normal Control

The azimuth controller computes the thruster position and order on the basis of signals 

from the thruster feedback and control levers. A two-wiper linear potentiometer 

provides two outputs with 90 degrees of phase shift named cosine and sine phase 

respectively.

The lever order signals and feedback signals are monitored and verified against alarm 

limits. If the signals exceed the limits this will release an alarm to the alarm plant with 

a visual and audible system failure alarm on the manoeuvre stations.

4.2.2 Backup Control

The Backup Control system consists of closed loop control identical to the normal 

control system. The Backup Control is a separate system, and is independent of the 

Normal Control system. A system failure in the Normal Control system will 

automatically switch to and engage the Backup Control.

Lever order signals and feedback are monitored and verified against adjustable alarm 

limits. If the signals exceed the limits this will release an alarm to the alarm plant with 

a visual and audible system failure alarm on the manoeuvre stations.

4.2.3 Backup Control Operation

If a failure occurs on important parts of the Normal control for the Pitch/Azimuth/RPM 

control function, the control will automatically be switched over to the backup control 

system. A system failure audible and visible alarm will be activated on each of the 

control panels.

The thruster control will continue to follow the lever in command, and command 

transfer is done by using the common in command buttons. The command can be 

transferred between all bridge position and the bridge control levers will continue to 

work as in Normal Control.

A failure that occurs on important parts of the Backup control for the Pitch/Azimuth/

RPM control function, will not affect the Normal control system. If a system failure 

occurs on the Backup Control an audible and visible alarm will be activated on each of 

the control panels.

4.2.4 Backup Control Limitations

The backup control system has only interface to the control levers. The backup control 

system does not have interface to external control systems like Dynpos, Joystick or 

Autopilot.

Note: No azimuth restrictions or load control functions are included in the 

backup system.

When operating using the backup system, the operator must be careful not to overload 

the engine or the propeller system.

4.2.5 Local Control

Local control is used if both the normal control and the backup control fail to operate the 

thruster azimuth. The thruster azimuth can be operated locally on the actuator unit. The 

Control System must first be disconnected from the actuator unit. This can be done by 

means of the Local Control switch mounted in front of the Actuator Interface Unit, or 

by disconnecting the plug from the actuator unit. If frequency converter used, operate 

service switch inside converter cabinet.

The Thruster Instruction Manual will give more details for Local Control operation.

4.2.6 Azimuth Indication

The azimuth indication system independent of the normal control system by means of 

separate transmitters and electronic circuits. The Azimuth indicators are connected in 

series, and are driven from the Backup Control system. 

 RPM Control

The RPM Control function system controls the speed signal to the frequency converter 

for electrical drives or the engine governor for diesel or gas engines.

4.3.1 RPM Control Electric Drive Motor

The RPM Control system includes selection of different operational modes:

• Separate Mode

• Combined Mode

Selection between modes is possible by means of push buttons. RPM Control can be 

managed from engine control room only or from additional control panels.

4.3.2 External RPM Control

External RPM order signals from system as DP/Joystick/Auxiliary systems can be 

connected to the rpm controller.

The external rpm signal are checked against adjustable preset limits. Any error 

conditions on the rpm input signal will initiate a warning to the alarm plant and an error 

message will be displayed on the control panel.

4.3.3 RPM Order Output

The output signal from the controller is scaled to meet the actuator signal range from idle 

to full rpm, and then fed to external governor, IP converter or frequency converter. The 

output will follow a linear curve between idle and full rpm order. 

The RPM output rate of change is adjustable and can be adapted to the engine/frequency 

converter reversing speed from idle to full rpm (increasing order) and vice versa 

(decreasing order).

4.3.4 Propeller/Shaft RPM Indication

The propeller/shaft RPM indicators are connected in series and are driven from the 

Backup Control system.

4.4 Command Transfer

The term Command transfer is used to describe the procedure performed when the 

control is transferred between manoeuvre stations without acceptance on either of the 

stations. This is normally the procedure between wheelhouse (bridge) stations.

5 Location of Manufacturing Number