could prove to be most troublesome dur- 

 ing switching operations and, in addi- 

 tion, would generate a substantial mag- 

 netic field which could be fatal for other 

 devices, such as magnetic compasses and 

 magnetometers. 

 — Another area sometimes overlooked is 

 the desirable separation of conductors 

 capable of carrying high level fault cur- 

 rents from conductors attached to explo- 

 sive-operated devices. A high fault cur- 

 rent could possibly induce a firing cur- 

 rent in the explosive squib and could 

 prematurely activate some system. 

 The foregoing considerations define the 

 tasks involved in the power distribution de- 

 sign. In general, the following recommenda- 

 tions are offered for these applications: 



— The connector or hull penetrator must 

 have a power rating in excess of the 

 maximum fault current which may flow 

 through the respective circuit as limited 

 by circuit protective devices. 

 — On all DC power circuits each polarity 

 should be taken through separate con- 

 nectors or penetrators. 

 — AC power circuits, especially three-phase 

 440 VAC, for example, should be carried 

 through a single nonmagnetic penetra- 

 tor or connector. Before attempting to 

 separate these conductors into separate 

 penetrators or connectors, a hard look 

 would have to be taken at the inductive 

 heating effects of these conductors sepa- 

 rated by magnetic materials, since detri- 

 mental, or even destructive, heating of 

 these materials could occur. If nonmag- 

 netic materials are used in the magnetic 

 field between conductors, the heating ef- 

 fect would be greatly reduced. However, 

 eddy current heating in any electrically 

 conductive material would still remain a 

 possibility. 

 — Circuits susceptible to noise or interfer- 

 ence should not be routed through a 

 connector or penetrator which carries 

 power and control circuits. 

 Regarding external distribution specifi- 

 cally, the importance of connectors (between 

 energy source and external distribution box) 

 capable of carrying the maximum fault cur- 

 rent generated by the energy source is em- 

 phasized. The group feeder breakers (Fig. 

 7.37) provide added connector protection be- 



tween the external distribution center and 

 the vehicle and the hull penetrator. In se- 

 lecting suitable sensing devices on the tie 

 and feeder breakei-s, the rating of the con- 

 nectors used in these areas must be suffi- 

 cient to handle the maximum fault amperage 

 which may flow prior to tripping a particular 

 breaker. The DOT Handbook further cau- 

 tions that penetrators through the hull 

 should be protected by circuit protective de- 

 vices to reduce the possibility of damage. 



As an aid in providing design guidelines, 

 component specifications and selection crite- 

 ria for circuit interruption devices, the DOT 

 Program undertook to produce reference 

 (45), the emphasis of which is almost entirely 

 on the use of on-off mechanical contactors in 

 pressure-compensating fluids. The author, 

 Pocock, states that subsequent editions will 

 include additional chapters on circuit break- 

 ers, solid state circuit interrupting devices 

 and fuses. 



INSTRUMENT 

 INTERFERENCE 



A great proportion of the instruments on 

 contemporary submersibles are electronic 

 and thus susceptible to electric interference 

 which can degrade their performance by 

 blanking out data or generating erroneous 

 data. Many of the instruments may be 

 classed as electroacoustic, which are also 

 subject to acoustic interference. Regarding 

 this problem, Mr. K. R. Haigh of the Admi- 

 ralty Experimental Diving Unit, Ports- 

 mouth, states (46): 



"T/ie presence, origin and nature of 

 electrical and acoustical interference 

 in the majority of current submers- 

 ibles has received scant attention from 

 the owners and operators with the 

 result that many users have been una- 

 ble to realize the full potential of the 

 boat in its scientific or survey role.''^ 



Haigh further reflects that such interfer- 

 ence is not a new problem but is one that has 

 been solved before in military submarines, 

 and he attributes its existence in submers- 

 ibles to lack of dissemination or suppression 

 methods to civilian submersible builders. To 

 appreciate that such interference can be a 



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