Principles of naval engineering - Historic Naval Ships Association

Chapter 25. -NEW DEVELOPMENTS IN NAVAL ENGINEERING(1) Stem Sensitive RTD(2) Thermowell with Adapter(3) Tip Sensitive RTD(4) Thermowell with HolderFigure 25-21.— Resistance Temperature Detectors.140.93Information leaving the scaling module fordisplay is sent directly to the Digital Display Buffersand Readouts (44) and appear at the readoutunits on the console face.The entire operation from pick-up of the inputaddress to activation of the printout unitsrequires a time span of .0376 milliseconds. Theassembly will monitor the complete bank of 273inputs in approximately two seconds providingthere are no requests or alarms conditions presentedto the system during that time period.THROTTLE CONTROLFigure 25-23 is a block diagram of thethrottle control system. A reference input signalmay be taken from either the bridge or engineroom reference handwheel potentiometer and fedto the system. Negative voltages are used forahead speeds and positive for astern. The signalthen passes through a common operational amplifierwhere it is inverted and then goes to thecommon circuit for both the ahead and astern turbines.The function generators will accept onlya signal of a given polarity. The ahead functiongenerator accepts positive signals and the asternfunction generator negative signals. The signalto the function generator is also used as a referencesignal for the speed feedback system. Thiscircuit compares the reference and speed feedbacksignals and uses the algebraic sum as theinput to the speed error amplifier.The signal to the function generator is adjustedwithin the amplifier so that the output isequivalent to the cube of the input. This is doneto change the linear movement of the referenceto the non-linear characteristics of the throttlevalve. Inversion once again takes place in thefunction generator.The output of the function generator ismatched with the speed error signal and thethrottle position signal at the summing junctionand the algebraic sum is fed to the summing amplifier.Inversion takes place and the output controlsthe action of the SCR power package.The SCR power package will cause the pilotmotor to drive in either direction depending uponthe input. A positive input will cause the pilot649