Patent GB-894972-A (GB)
Title: Improvements in or relating to position indicating apparatus
Inventor: CAMPBELL RONALD HUGH
IPC: G08B25/00
Filed: 1959-07-06
Abstract: 894,972. Measuring electrically. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. July 17, 1960 [July 6, 1959], No. 23107/59. Class 40 (1). Apparatus for monitoring the positions of a number of synchronously adjustable members comprises a position transmitter associated with each member, a receiver whose rotor represents, by its angular disposition, a reference position, a switch whereby position signals from the transmitters are fed to the receiver cyclically, a servo loop responsive to an error signal produced by difference between the reference position and the position being signalled to the receiver to rotate the receiver rotor to eliminate the error signal, and alarm means operated when the error signal exceeds a predetermined level. As shown, Fig. 2, the linear position of each of a plurality of control-rods in the core of a nuclear reactor is represented electrically by the threephase output of one of synchro transmitters 1... 18, which are actuated by motor units controlling the positions of the rods. The transmitters are cyclically connected, via a uniselector switch 30, the wiper of which is operated by an indexing motor 51 to remain at each position for a uniform time, e.g. 30 seconds, to a common synchro receiver 34, and to the actuating mechanism of a pointer 53 (see also Fig. 3) which co-operates with a scale 54 to register the position of the rod being scanned. Misalignment between a transmitter and the receiveer 34 produces an error signal in the latter which is amplified in a non-thermionic (e.g. transistor) amplifier 38 and used to operate a motor 35 to drive, through gearing 36, the rotor of receiver 34 to its null position. The output of a tachometer generator 41 on the motor shaft is fed degeneratively back to the amplifier. A second uniselector switch D, operated in synchronism with 30, controls circuits containing lamps 55 which are illuminated in succession to indicate the rod being scanned. When the rods are stationary in the same relative positions, or are moving into or out of the reactor core in synchronism, error signals are zero or comparatively small; if, however, one rod is out of position relative to the others, scanning that one rod produces a large error signal which energizes a relay 43, thus opening contacts 40 to prevent the receiver rotor following the out of line transmitter, and closing contacts 45, 46, to operate an audible or visual alarm 47, and to stop indexing motor 51, respectively. Scanning is resumed by pressing a button 56 (Fig. 3) corresponding to the erring rod; this closes contacts 57 (Fig. 2) to energize a relay 32 which opens contacts 31 in the line from the relevant transmitter and closes contacts 59 to apply a stepping potential to the relevant fixed contact of a third uniselector E. Thus the rod which caused the alarm is by-passed in scanning until it is re-introduced by operation of a button 58 which releases contacts 57. If any of the control-rods is intentionally misaligned, the relevant transmission circuit is provided with a manuallyset synchro differential to compensate the transmitter output for the effect of the misalignment.