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Inverter Unit

Technical Information

Catalogue No: C1023
Category: Navigation/Inertial
Object Type: Power Supply/Conditioner
Object Name: Inverter Unit
Part No: CD11951
Serial No: R02FJB204
Manufacturer: Elliott Bros
Division: Unknown
Platform(s): Navy Equipment 
Year of Manufacture: Unknown
Width (mm):
Height (mm):
Depth (mm):
Weight (g):
Location: Main Object Store

Inverter Unit
N.S. No. 6605-99-529-2383
Drg. No. CD11951
Ser. No. R02FJB204
WT. (kg)
DL Iss. 15


The Naval Compass Stabiliser NCS1 is a stabilised gyrocompass system designed to provide heading and vertical reference data for systems that use such data, on board a ship. Development of NCS1 started in 1971 and quantity production was underway by 1976 with 80 systems delivered to British and other Navies by 1984. NCS1 provides as standard outputs of Heading, Pitch, and Roll but with an additional card can give own ship acceleration and velocity. The ships Latitude and Longitude are continuously computed.
There are three major units; Space Reference Unit (SRU), Electronic Pack (EP) and a Mount Assembly. The SRU comprises a stabilised platform containing 2 two axis gyroscopes and 2 single axis accelerometers mounted in a gimbal system which is contained in a closed binnacle with associated control electronics. The SRU is protected against shock by the Mount Assembly which provides the interface to the deck.
The EP contains power inverters, a digital computer, control /indicator Panel and a standby battery. The Transformer Rectifier units convert ship’s power to 28v dc and in the event of a supply failure the standby battery will support the system. Two identical controlled inverters produce all the regulated dc supplies required by NCS1. The computer is the 12/12P, a variant of the standard Company unit. The Interface Unit carries out such functions as synchro digital conversion, analogue to digital conversion and the reverse, signal buffering and built-in test. A Control and Indicator panel hosts switches and displays to select the mode of operation, set in information, display selected outputs and enable computer controlled or manual testing.
Initial sea trials were carried out in HMS Antrim. NCS1 was designed and manufactured within the Guidance Systems Division at Rochester between 1976 and possibly beyond 1984.
This is one of the Inverter Units from the Electronic Pack.

The NCS1 is a tall unit and there is a story that in order to calibrate the system using the Pole Star that a hole had to be cut in the roof of the clean room test area!

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