Upholder/Victoria Class Propulsion
Postulated Diagram of the Electrical Propulsion Layout of RCN Victoria Class Diesel-Electric Submarine
Postulate: Suggest or assume the existance, fact or truth of (something) as a basis for reasoning, discussion or belief
A comprehensive GEC article received some years ago, confirmed that the single large GEC double armature motor Fig 1a & Fig 1b, was in principle similar to the much smaller motors of submarines of some 60 years ago, found in pairs in twin shaft A Class and T Class submarines of WW2 vintage Fig 8a. Thus the basic switching control requirement to operate this type of motor was already known to the author from past experience. A review of the GEC article is to be found in Part 2.
In these earlier boats, all the heavy knife switches were manually operated by a Watch Keeper and ordered from the Control Room by a traditional mechanical telegraph Ahead Slow etc and an electrical operated Grouper telegraph, with the Watch Keeper advising he had acted as ordered by pressing a push button to ring a gong in the Control Room.
The Converted T Class designed about 1948, followed the same telegraph order principle, but the manual switching was a mix of heavy manual knife switches and manual Starting camshafts, one set for each of the four motors - two per shaft.
The P Class of 1958 followed, still manually controlled and responding to an order system (see table Fig 10a), but with a locally controlled, pilot motor operating the Starting camshaft and a manually operated Group camshaft. The similar, but improved O Class followed in 1960, retaining the same electrical propulsion as the P Class and order system (Fig 10b.
The RN Upholder Class > RCN Victoria Class eventually followed - the GEC Motor article summary in Part 2 Notes, indicates the first of class was on the drawing boards as early as 1979. From now on only the RCN Victoria Class name will be used in these notes unless inappropriate.
On the Victoria Class, the need for both camshafts to have pilot motors, becomes clear when it is understood that a remote order or control system - effectively takes the place of the Motor Room Watch Keeper of the past, the One Man Control system, adjacent to the Helmsman in the Control Room. Fig 5a & Fig 5b.
Expert Advice Received
Here are three informative messages from people with expert knowledge of the propulsion system that helped clarified other research.
Mr Hulme, Main motor has double armature control by a grouping cam and starting cam. Speed adjustment is done by amplifiers for each grouping. Pretty well the same technology as WWII.
There are 2 circuit breakers, one for each battery. It provides the submarine with more redundancy and it allows operator the ability to use one battery for propulsion. Batteries become unbalanced for various reasons and have to be discharged (same power/voltage). The circuit breakers for the propulsion switchboard are rated at about 3500 amps.Expert Advice 1
Mr Hulme, I will try to answer your questions to the best of my ability but as you have already alluded to a tour in person would benefit us both for an easy explanation. Essentially just like an 'O-Boat' the telegraphs are rung up in the control room and passed to the motor, but unlike an O-boat where I was the control system as the second motor room watch keeper, there is an automatic control unit (ACU) that positions both the grouping and the starting camshafts to the requested positions. The required RPM is also passed to the ACU and the system sets the RPM automatically. The appearance of buttons on the machinery control panel in the motor room is just indication so the motor room watch keeper can monitor the motor movements and system parameters.
Now if you are speaking about the buttons and rheostats on the motor control panel then, when that in engaged in local control then it is operated just like an O-Boat by the second motor room watch keeper. The cams are motor operated by the selector switches on the panel by the operator, and you are correct in assuming that the two dials control RPM and balance, with the grouping and starting cams being operated by the selector switches located on the right side of the panel. Just like an O-Boat the whole panel can be operated in Remote, Local remote and local Hand control. Hope this help.Expert Advice 2.
Mr Hulme, here are some notes etc that might be of value. You are quite correct, local control is on the Propulsion Switchboard (Secondary Control as well as Manual Mode 1 and Manual Mode 2)
Mr Hulme. The MCC is a Remote Operators Panel for the Diesel Generators and Auxiliary systems such as Motor Generators, Saltwater Cooling, Freshwater Cooling.Expert advice 3 (ex-RN).
There are also number of Internet Videos of media tours of this class of submarine in RCN service that have proved to be quite useful.
Submarine Association Of Canada (East) has provided contacts that have been most valuable and in particular, gratefully thanked are former submariners - Brum Tovey and Billy Dobson UK.
Notes on the preparation of the main diagram
This diagram has been built up progressively in a boxed colourful style so that as information and images came in from various sources, modifications could easily be applied. It has been left in this style in the hope it will also assist the reader's understanding. It is a diagram of a workable system, but accuracy in relation to relative placement of the MMBs and the Starting Contactors of the Victoria Class is a case of best endeavours, based on the limited expert advice available, some of it apparently contradictory and unable to be clarified, Reference is made as appropriate, to the preserved Alliance with dual armature motors and an image of her port switchboard is included. Fig 8a
T2400 Propulsion Switchboard
This large grey painted cubicle of some 4 tons and about 4m long, is secured above the length of the Main Motor,(as are the switchboards in the Alliance), it obviously keeps the heavy current leads as short as possible. In the cubicle compartments Fig 3c are the various elements of the heavy current motor switching shown in the main diagram and could be called the heart of the Main Motor control. At one end of the cubicle is a local control and indication panel, divided for purpose into three panel sections.
Fig 3b shows important basic aspects of the electrical motor propulsion such as Armature and Field Ammeters. It should noted in Fig 3a the RH panel section replicates the One Man Control at the Helm, Fig 5a & Fig 5b, for use when local operation of the remote control system is required when snorting or charging. There is an Automatic Control Unit (simply a grey box) that is mounted on the top of the cubicle shown in Fig 3c that could be called the brain, that takes the operator's orders (helm or local) and ensures they are executed and reports back.Lower down the front panel Fig 3a are Starting and Grouping manual camshaft options in the case of pilot motor failures.
Note - the 3500 amp ammeters are fed from a transducer in the main supply lead to each armature (see diagram). This is connected by a light current lead looped to the various armature ammeters on the consoles and T2400 Propulsion switchboard. Similar tranducers will be in the Battery and Generator leads.
The two large, internally electrically separate, DC Cumulative Compound Motors, are in one casing and on one shaft.Fig 1a & Fig 1b It would possible to start the two armatures via a common starting resistor and switches as in earlier small twin shaft submarines, but this is unlikely to be the case in the Victoria Class.
Each armature is started by applying the supply (battery) voltage to the armature via a substantial resistor to limit the current while the speed is built up. The resistor is tapped at several by - pass points so that it can be progressively reduced in value until the motor is at full speed and a contactor closes to completely bypass the starting resistor.This contactor has to be capable of carrying the maximum armature current in service. 3,500 amps per armature.
In a submarine like Victoria Class with one dual armature motor, there would be as much separation of the two armature systems as possible, with the damage control possibility of using only one armature (See incident report in Part 2 General Notes).
For the technically minded, the motor while rotating, acts as a generator producing a voltage in opposition to the supply voltage, thus limiting the current - beyond this, the principle should be studied in a text book - such as the still excellent Examples In Electrical Calculations - Admiralty BR 158 (52), replacing the 1933 edition, there are second-hand copies available.
The number of taps per resistor chosen is arbitrary on the author's part. The calculation of the number of taps and the value of each resistor section, is a relatively complex calculation that serves no purpose in the reader's basic understanding of the control system and is demonstrated in any electrical machine text book such as that mentioned above.
Armature Control - as shown in the diagram.
The overall control of the dual armature (A1-A2) motor is achieved by the various sets of contacts shown in the diagram, these being mechanically operated by two separate systems of camshafts driven by rods and maybe gears, in turn driven by pilot motors controlled by the Automatic Control Unit Fig 3c and remote control, usually the OMC Fig 5a. or if snorting or charging, then locally at the RH panel of the T2400 Switchboard Cubicle Fig 3a. The camshaft contacts in turn, closing the operating circuits of the heavy current contactors.
Note that all the contacts shown on the diagram are associated with the currents supplied to the armatures
The pilot motors (not shown on the diagram) are supplied with three phase 440 volt 60Hz and can be brought to an abrupt stop by removal of the power supply and +24 volt DC applied to two of the three terminals.
The Two Camshaft Operated Switch Systems.
Unfortunately no detailed description or image is available of the Victoria Class camshaft system, however there are indications of the likely basic design from earlier submarine systems, for instance, see Fig 10a, top paragraph that briefly, but clearly describes the P Class & O Class camshaft, with reference to a Geneva wheel and clutch. Geneva wheels are used in the Power industry in On Load Tap-Changers found on large power transformers for voltage control and no-doubt in similar mechanisms enabling step motion to be derived from continuous motion. Examples may be found on the web.
The official BR 1965 T Class Conversion 'Electrical Manual', tells in detail with images, of the hand wheel operated Start camshaft, with Geneva wheels and clutches, so we can assume with some confidence, that the Geneva wheel camshaft principle that served the RN in the Fleet of diesel submarines throughout the Cold war, would be similarly used in the camshaft systems of the Victoria Class
In the Victoria Class, one five position camshaft system (Grouping) is used to select the armature and battery interconnection arrangements > Slow - Off - Group Down - Group Up - Batteries In Series. Fig 9a The other camshaft (Starting) is then used to first, to set the contacts for the selected direction of rotation of the main motor and then go through the Starting sequence, progressively shorting out starting resistance taps until the motor reaches full speed, when the speed can be further increased by reducing the shunt field current.
There will be a reliable system of electrical and mechanical interlocks to prevent incorrect selection of contacts. The Alliance has a various mechanical and electrical interlocks, including the engine clutch.
In the diagram, the contacts are all shown numbered by the author's arbitrary system, with prefix letter indicating their function. The individual contact state (Closed or Open) is shown in boxed lists, coloured to show which of the two camshaft systems they belong to.
As previously stated in the summary, it has not been possible to get any diagrams or images to show the mechanics of the camshaft operated switches or the type of heavy current contactors.
One concern regarding the diagram was that with each of the two armatures of the Victoria Class having twice the maximum current of one of the four, P Class & O Class armatures - in the order of 3500 amps, very large camshaft switches would be required, however a reliable source has advised that intermediate relays are energised by relatively light Camshaft contacts where heavy currents are involved. These relays have contacts that operate the closing mechanism of heavy motor current contactors. If this is the case, the camshaft operated contacts shown on the diagram will be those of the heavy current contactors operated by intermediate relays, in turn operated by the camshaft switches.
Apart from the Grouping and Shunt Field Control of the two armatures of the Main Motor, a facility is available to disconnect the direct battery supply from the forward armature and supply it with the output of a motor-generator supplied by the Variable Pressure ring main from the main batteries.The contacts etc are in a cubicle shown in Fig 3c. The forward main motor shunt field is set at a fixed value and the armature current and thus speed, is controlled by varying the output voltage of the M/G generator field set. This combination of three machines forms a Ward - Leonard set, a speed control system invented in the late 19th century that until possibly the arrival of the latest Power Semi - Conductors, was the best electric motor speed control system available, albeit somewhat expensive (there are articles on the web). This method of Creep or Slow Speed is a substitute for the ability in the Alliance and the P Class & O Class to put all four armatures in series, dividing the battery voltage across each for the Slow Speed.
The Two Shunt Fields - one each for the two armatures -fore and aft
One major difference from the O Class, is the use of electronic converters to supply the shunt fields - one per armature. This enables the speed within any Armature Group to be controlled by the Automatic Control Unit that reader will recall is fitted on top of the T2400 Propulsion Switchboard (aft in the Machinery Control Room) Fig 3c and consequently fine tuning the speed of the Main Motor, that can propel the submarine up to 20 knots submerged.
It is understood, there are critical speeds that if avoided propeller cavitation will be reduced,. The detail is not available. However there are number of scientific papers stating that any modern submarine going astern when submerged to quickly reduce speed, can produce a noisy vortex around the screw, as the submarine is still moving forward while the propeller is going in the astern direction. Apparently on some submarines (Fast Nuclear?) loss of control by the hydro planes can be experienced going astern in this manner, if the submarine hull is actually allowed go astern. An optical decoder is somehow used in the Field Control. It is assumed this is involved in some system that detects the position of the shaft as it rotates, a common use of optical de-coders, but the full nature of what is involved is unknown. It is said many developments for the earlier nuclear submarines were incorporated in the design are perhaps classified. Perhaps more will be revealed on this topic in the future?
The importance of the Shunt Field control is emphasised by, apart from there being one Field Converter per armature, there is a spare and manual option, but the emergency manual field option set-up, is not known, but in some manner it will be from the only source - the batteries.The Field Converters cubicles are fitted apart from the T2400 Propulsion Switchboard.
History - an older 'U' class submarine
The RN has done a lot of investigation into submarine screws since the commissioning of the HMS. Scotsman in 1948 as a fast trials submarine and there should little doubt the Victoria Class propeller will be quiet. But this was not the case with the numerous earlier U Class that bravely contributed so much in WW2 despite suffering from Singing Propellers. From the early appearance of Scotsman after WW2, one can assume the RN intended to intensify the study of submarine screws and noise, in preparation for future submarines.
The Machinery Control Room
The Machinery Control Room (MCR) is located near the aft escape hatch. Fig 9c.
The Machinery Control Room has a substantial Operator's Console (MCC) for the Diesel Generators and Auxiliary systems such as Motor Generators, Salt-water Cooling, Freshwater Cooling. In the same general area aft, are located the Main Motor and T2400 Propulsion Switchboard and called the motor room as in older submarines.
There is a small section of the desk console in the MCR that is concerned with the electrical propulsion Fig 4a that indicates only, the state of the propulsion system to the MCR Operator - such as the Main Battery Voltage, Groupings, and the Armature current as displayed in the T2400 Propulsion Switchboard located over the main motor Fig 3b. On this section Fig 4a there is an armature amps display by two analogue ammeter each centre scaled to show the maximum currents in the order of 3.5kA at high speed (Ahead or Astern), while the two 3-digit displays show the low current at slow speed. At the top are digital displays of the two main battery voltages. The state indicators of the two Main Motor Circuit Breakers and the grouping are discernible at the bottom of the image. It has not been possible at this time to precisely determine the use of the row of knobs and switches beneath the row of black MMB and Group Indicators. Efforts to find out will continue.
- Primary - controlled by the Helmsman in the Control Room operating the OMC (One Man Control) Fig 5a and Fig 5b via the ACU (Automatic Control unit) to the T2400 Propulsion Switchboard Fig 3a, Fig 3b and Fig 3c
- Secondary - Control - Motor Room Watch Keeper - at the panel on the T2400 Propulsion Switchboard 3a similar to the OMC, via the ACU. Especially when snorting and charging.
- Manual Mode 1 - Controlled by the Motor Room Watch Keeper at the T2400 Propulsion Switchboard (ACU not available). Note the two hand wheels to manually operate the camshafts. Fig 3a
- Manual Mode 2 - No ACU and no Armature Field Converters. Fields fixed.
There is little merit in going the detail of various switches for Manual modes as this is not a training instruction.
Summary of Motor & Control Notes
The Victoria Class Control Room watch helmsman operating the OMC Fig 5a & Fig 5b can set the basic propulsion requirement as in earlier submarines such as grouping and Ahead/Astern etc, but once propulsion status is ordered, instead of a Motor Room Watch Keeper setting the propulsion manually Fig 10a and Fig 10b, the ACU. performs this role and sets the grouping and field currents to obtain the ordered speed. It can be seen there is an Ordered RPM indicator together with an Actual RPM indicator in the Helmsman's position and similar on the T2400 Propulsion Switchboard. These digital indicators have been included in the diagram
It is important to reiterate that provision has been made on the T2400 Propulsion Switchboard for a control panel Fig 3a identical to that in the OMC in the Control Room Fig 5a. and normal remote control is transferred aft to the motor room panel under certain operating situations such as snorting and battery charging. And that provision is made for manual control of the two camshafts in event of Pilot Motor failure or if the ACU fails. A spare Shunt Field Converter is provided and other provisions to maintain the essential shunt fields.
Included is an image Fig 8a of the port Switch Board of an A Class submarine, the preserved Alliance, that controls the dual armature motor on the port shaft. The main switches are clearly shown and labelled. The motor is much smaller than the single Victoria Class motor (17.5 vs 83 tons), but requiring same switching for Grouping, Ahead/Astern and Starting through resistors. The older-style large dual ammeters show the Armature current -motoring or charging, as does a similar ammeter showing battery discharging or charging currents. These instruments are to found in Victoria Class, but in a modern, smaller style, with the qualification that submarines like the Alliance, also employ the dual-armature motor as a generator for charging, but this does not prevent Alliance being used as an open demonstration of the basics of the more sophisticated switching, in cubicles, in the Victoria Class.
To avoided confusion, comparison is being made with only one of the two motors on the twin Alliance, also it should noted the armature current at maximum speed is quite high as the battery voltage is nominally only 220 volts, dropping with load (Power = Voltage x Current). Thus the open Alliance switches are quite heavy, being for currents in the order of 1200 amps and this aids a sensible comparison to be made with the Victoria Class.
A simple circuit is shown and the Sw Brd components labelled. The single knife switch (LH) is not provided in the single shaft Victoria Class, as this was to enable the four armatures of the A Class to be placed in Series for Slow speed as describe above. Also there is no switching to select whether the two main batteries are in Series or Parallel - Series for High Speed. This battery grouping system was first installed after WW2 in the RN to increase the motor voltage for high submerged speed, in the converted T Class and the P Class & O Class.
To introduce some submarine history from before WW2 - a small number of the famous wartime S Class had a single armature motor on each of the two shafts and grouped the battery, divided into two parts, to gain the two ranges of speed. This was later discarded in favour of armature grouping with the batteries permanently in parallel. As the Alliance is now.
The two batteries are in two tanks separated by a main bulkhead. Fig 7e. They are basically similar to tanks in earlier classes in being stepped to fit the circular hull and finished to contain acid leaks and a sump to collect leaking acid, that has a viewing port and connection to the ship's pumping system. As in earlier submarines, the cells sit, wedged, on waxed teak gratings that ease the movement of cells for removal. Fig 7f.
At about 550 kg each cell, this is a difficult operation with only the access hatches to lift them through, requiring some chess - like moves to get the faulty cell under the hatch. Fig 7f
The heavy current from the battery to the Battery Switchboard Fig 7b passes through carefully placed Equalising Cables that create a magnetic field that cancels the field produced by current passing the through the battery itself. (This is also the case in the Alliance)
Each of the two Battery Switch Board has a main Circuit Breaker that connect the battery to the main bus and the Auxiliary Circuit Breaker that as is implied feeds the various auxiliary supplies.
As indicated on the diagram, the batteries are charged by the two Diesel-Generator sets, that other than mentioning them, are technically beyond the scope of this article - here is an image of the two D/G Circuit Breakers that connect them to the main bus. Fig 7a.
More information on the engines may be obtained at the Paxman History web site. However the obvious will be stated - one of the attributes required of modern submarine D/G sets is the ability of high speed engines to stand the stresses of snorting - the low speed, direct drive, four stroke engines of the Alliance seemed to the author to be robust in this regard. It is interesting to compare the Victoria Class engine (2010 bhp at 1350 rpm, max 1418 rpm.) with the Alliance (2150 bhp at 460 rpm).
It has been difficult to find console images of the Main Battery charging instrumentation (Basically Battery Amperes & Volts) in both the Control Room and MCR aft apart from Fig 5b & Fig 7c, however from the Victoria Class information available, there is every reason to believe the charging regime of the Victoria Class is very similar to that of the earlier O Class that is described in detail in the Canadian Forces, O Class Submarines,Training Notebook and specifically the aft 'O' Main Battery instrumentation and controls, are listed here Fig 7g
Battey Cell Ampere/Hour Capacity
The 5 Ahr rates for RN Submarine Battery cells have risen considerably since WW2, for instance the T Class - 5350 and A Class - 6630. The major change in regard to all aspects was seen the P Class & O Class - 7420, until Upholder/Victoria Class 8800. Also the number of cells has increased per battery - O Class 224 cells in each of the two batteries - in the Victoria Class 240 cells in each of the two batteries. A nominal power increase of 27%. from the O Class to the Victoria Class. The mass of each cell is similar to the O Class cell.
This does not seem sufficient to provide the Victoria Class Main Motor with the power to achieve 20 knots for an hour and still have some capacity for slow operation, while the O Class could only sustain 17 knots for about 20 to 30 minutes and this with 2 x 3000 shp Main Motors. But no doubt the hull shape and efficiency conferred by a single propeller, contribute considerably to the performance of the Victoria Class.
Efficient hull design kept propulsion loads and discharge rate low, despite the increased operational electrical load. Patrolling at slow speeds would require 40 to 60 minutes of snorkelling per day; a transit at 8 knots would require snorting approximately 30% of the time. Top speed submerged matched that of any similar SSK and could be maintained for more than 90 minutes from a fully charged battery. Further, once a submarine reached the end voltage, it still had considerable capacity remaining for operationally useful speeds.
He also commented that the Unseen was an excellent submarine, ideal for giving young Captain's experience before moving to SSN.
The development of the USN Guppy conversion submarines and the considerable increase in cell capacity in the same volume, is detailed at length in USN Guppy Conversions
The management of the safe disposal of the hydrogen gas, has become more and more critical as the capacity of the cells has increased, installed in relatively small internal hull volumes. This is particularly so when snorting and in the Victoria Class that all practical steps appear to have been taken, including a comprehensive main battery ventilation system, Hydrogen Clearance fans and Palladium Hydrogen Eliminators, with Hydrogen detectors located at critical positions. To see the battery ventilation of the RCN O Class, see Snorting in the Royal Navy, 1945 onwards
Commander John Powis RN (ret) advised the author that in the Unseen, gassing charges had to be carried out in harbour and Captain (S/M)'s permission granted.
Conclusion Part 1.
Every attempt has been made to give an accurate description of the Electrical Propulsion System of this former Royal Navy Class of Submarines, now in service with the RCN, but the fact they are in service means that unlike past articles on older submarines classes that are out of service, detailed crew manuals and dockyard drawings are not available. Fortunately contacts with former RN crew members have been made and they have been very helpful as have contacts at SOAC (West) Canada, thus it is believed this article gives a reasonably accurate view of the electric propulsion of the Victoria Class submarine. Unlike other RN submarines, their short period in the service of the RN has not produced as many anecdotes as has been the case in the past article.
General Notes on the RCN VictoriA Class submarine, formerly the Upholder Class of the RN, originally designed by Vickers as 2400.
These notes complement Part 1 - the diagram and technical notes that are focused on the electrical propulsion of the Upholder Class submarine of the Royal Navy, developed by Vickers as 2400, four in class, transferred to the RCN as the Victoria Class class. This article on the Electric Propulsion (including diagrams, images and explanatory notes) is rather different in format from earlier articles, as it has proven rather difficult to get detailed official technical information about a submarine class in service. In the case of the article on older T Class conversion and the P Class & O Class, official manuals became available, together with other documents. Also the Upholder Class did not serve for very long in the RN before being decommissioned for some years before being purchased by Canada. This means there is not the same large pool of RN ex-submariners who served on the Upholder Class as was the case with older classes, who might have been able to provide the informative anecdotes as they have in the past.
From here only the current RCN class name - Victoria Class unless otherwise appropriate
The notes follow on articles also posted on this web site, concerning the electrical conversion and streamlining of eight T Class (programme commenced 1948) with an appendix about the electrical propulsion of the P Class first commissioned in 1958, followed by the very similar, but improved O Class 1960. The P Class & O Class had twin shafts and thus two dual armature motors - the total power was 6000 bhp compared to the Victoria Class with 5400 bhp, however the significantly larger battery and modern hull shape with the more efficient single screw, gave the Victoria Class a superior submerged speed and endurance performance. Fig 9b
The modern approach to the control of all aspects of the submarine's operation enables a substantial reduction in crew - it is tentatively suggested this enabled a overall improvement in design in that the reduced accommodation space kept the volume down and thus the displacement, despite a substantial increase in battery size and other equipment. For those wishing to pursue this aspect of the overall design the author suggests Concepts In Submarine Design, the authors of this book based it on the Vickers 2400 design that became the RN Upholder Class. They were academically based submarine consultants involved in the design of the 2400 and very readable for those wanting to increase their basic knowledge of submarine design. Authors - Burcher and Rydill.
Submarine Propulsion Machinery
It is worth considering the matter of redundancy of propelling machinery in diesel submarines. Immediately post WW2, the USN consulted submarine captains about the future and one thing in particular emerged - they were not happy with the idea of a single screw, but as was pointed out to them there was no recorded case of a US submarine returning from patrol on one screw (Admiral I J Galantin USN (ret Submarine Acmiral). Nevertheless the first post WW2,USN New-Build class was the twin screw Tang, as were the first two SSN. Quite separately the USN saw a need for a fast unarmed target submarine and thus the Albacore design was developed after much thought by the scientists, using model trials at the David W Taylor Model Basin - USN Portsmouth Naval Shipyard, based on the British R101 and the USN Akron airships. Series 58 model of hull shape that is apparently known as a body of continuous revolution.
As an aside. It is of interest to note that amongst aerodynamic articles studied were those of the British mathematician, Hilda Lyons, and in the early stages of the project, official US comparative power/speed curves were issued showing submarines in service at the time and the new submarine called the 'Lyons Shape'. Ms Lyons (a Cambridge mathematics graduate) had been in the team of mathematicians designing the R101, but had no personal contact with the people designing the new USN submarine, having been deceased for some time, though its of interest that shortly after the unfortunate crash of the R101 due to fuel problems, Ms Lyons took up a Masters scholarship at MIT in the US, working on the wind tunnels with a variety of airship hull shapes, her Thesis is published on the web. She returned to the UK and worked successfully in the aircraft industry until her premature death in 1946. She produced quite a number of papers on matters concerning Aerodynamics that could and were applied in Hydrodynamics. The now, public report on the Albacore, from the David W Taylor Model Basin, acknowledges Ms Lyons articles in the reference list.
The USN went on the build the successful Barbel class based directly on the Albacore hull design. Only three were built, as the USN moved to become a solely nuclear submarine navy.The plans being later passed to Japan and the Netherlands to produce submarines based on the Albacore hull. A USN civilian expert advises the author, that after applying the Albacore design to the SSN Skipjack, the USN carried out a number of trials at the David W Taylor Model Basin (report public 1955) to determine the effect of introducing a cylindrical mid-body into the tear drop (Series 58) shape and the loss of speed was found operationally acceptable with a significant gain in space for men and equipment.
This then is the shape of the Victoria Class, not the perfect Albacore hull 'Tear Drop' shape, as so often stated.
To continue the redundancy theme - until the 1958 P Class, RN submarines like the A Class had a twin shaft propulsion drive, where the diesel engines could drive, through the engine clutches, through the electric motor's shaft, through the tail clutches to one of the two screws giving options in case of failure.
The WW2 U Class was an exception, being small and and before 1939, intended only for training in local waters. Fitted with twin D/Gs and motors - possibly because the small hull prevented the in-line shafts of the direct drive propulsion? There would have been a saving in having no shaft clutches. Also the mass of the higher speed engine would be smaller for the same bhp - but all this is speculation.
Following the converted T Class still with the direct drive if required and the unmodified, but streamlined A Class Fig 8a, came the 1958 P Class, apparently delayed by post-war costs, followed by the very similar and successful O Class, where the diesel engines only drove electric generators to charge the batteries and supply the electric motors that turned the twin screws. It is beyond the scope of this article whether or not the Victoria Class was a normal successor to the ageing O Class, but rather a class built for a specific purpose in the Cold war?
In regard to the Victoria Class, it is to be assumed that every design effort was made to allow a single armature to propel if the other failed. For instance separate starting resistances as has been assumed in the diagram Part 1.
It is worth noting the VII C U-Boats of WW2, were basically similar to the Alliance with direct drive and continued this practice in the famous XXI fast U-Boat with engines and motors geared to the propeller shaft. Notably, after WW2, the German Submarine builders, having raised a sunken XXI and converted it as a trial and development boat (1960),the Wilhelm Bauer (U-2540) and changed the propulsion machinery from direct drive to diesel-generator sets and separate electric motors driving the twin propellers. And as is well known they have gone on to build successful submarines with modified Albacore style hulls.The Wilhelm Bauer is now preserved at Bremerhaven.
A significant change in RN diesel submarine propulsion design, was the use of electronic converters to supply, adjust and stabilise the two motor shunt fields in the Victoria Class instead of the manual rheostats used in earlier submarines for controlling the field supply from the main batteries on the Port & Starboard switchboards adjusted by substantial hand wheels, as can seen on the preserved Alliance Fig 8a, that needed an involved shaft and gear system between the switchboard hand wheel and the variable contact mechanism on the large air cooled resistance box mounted at the back of each switchboard. Each field of the two pairs of Shunt fields had their own rheostat, but manually adjusted on each side, by a common mechanism.
Whether a similar electronic shunt field control would have been of value in the design of the earlier submarines is irrelevant as power semiconductors were way in the future.
The Main Motor of the Victoria Class submarine is a modern version of the type of motor used in RN Submarines since at least 1920's. The overall design of this submarine having been apparently conceived about 1978, it can be assumed the latest materials and techniques were employed, particularly in the commutator area, improving reliability. It would reasonable to say that the well tried, conventional motor used in the Victoria Class was a sound choice, using electronically controlled shunt fields, that enable sophisticated remote speed control within each armature/battery grouping speed.
To use any other type of motor with the main battery DC supply as in submarine, required a radical design in overall motor design such as that found in the modern German design by Siemens (trade name Permasyn), using permanent magnet excited AC motors and Insulated Gate Bipolar Transistors electronics. However it should be noted that Siemens are currently also offering a version of the DC Dual Armature motor (trade name DC Prop), very similar to that found in the Victoria Class.
It is also notable that main motors of the Swedish designed RAN Collins submarine (6 in class) are also dual-armature motors. Albeit larger at 7400 HP, built by Jeumont-Schneider, with the overall submarine design approved in about 1987.
Creep - Slow Speed
With only one double armature motor in the Victoria Class, it was not possible, as had been the case on the O Class and earlier classes to connect the four armatures of two shafts in series for a creep speed, so there is an arrangement where the single forward armature is diverted from the main battery supply to the output of a Motor Generator Set. Described in Part 1 and shown in the diagram.
Soviet practice of the time was to provide a small creep motor with armature on the main shaft. The well known WW2 type XXI used V-Belts to connect creep motors to the shaft. The earlier twin shaft RN submarines, were able to connect all four armatures into series, reducing the voltage applied to each armature, hence lower RPM. It is stated the Australian RAN Colins Class, has a separate hydraulic drive and screw.
The Double Armature Motor
Comment on and extracts from a technical paper by the Manager of GEC Alsthom Large Machines Ltd
Comment on and extracts from a technical paper by the Manager of GEC Alsthom Large Machines Ltd
Dr Ian Buxton kindly made available a copy of Electrical Propulsion for Conventional Submarines by R Pratt, GEC Alsthom Large Machines Ltd, dated 1989, that describes in detail the design of a large double armature motor Fig 1a & Fig 1b, suitable for the 2400 submarine. It is interesting to quote from the article:
In 1979 GEC Large Machines carried out a design study for Marconi Command and Control Systems on behalf of the Ministry of Defence, on a new propulsion system for a conventional (conventional in the sense it was not nuclear) submarine to replace the O Class. A number of designs were considered, to suit the overall length, diameter and weight restrictions laid down in the specification
Then the article goes on to detail features that are beyond the technical scope of this article, however it seems that a non-compensated machine was chosen unlike the motors of the past (the details of the consequence of this change can be studied in any Electrical Machine book). The bearing arrangements as described are quite interesting - there was end float allowance of 16 mm for hull deflection when diving and when subject to depth charge explosions. Great care was taken in the commutator brush design. The author's experience in older submarines, like the A Class & T Class, was that the main motors were very reliable in peacetime service.
Battery and Motor Configuration (Submerged)
The article provide the basic detail about the two solid state converters, one the forward machine (armature) and one for the aft machine (armature), with one emergency spare. They enable automatic field control in all modes of propulsion and there are two manually operated back-up regulators in the event of failure in the automatic mode. One point the author makes, that should be noted, is that the voltage of each battery varies over a wide range (typical 2:1) depending on whether charging or discharging.
|Battery and Motor Configurations|
|batteries in series, armatures in parallel.
batteries in parallel, armatures in parallel.
batteries in parallel,armatures in series.
Efficiency - here as stated verbatim in the paper by R Pratt:
The overall objective for the vessel is to maximise cruising range in all modes of propulsion when on battery supply.The requirement for high efficiency at low propulsion power is very significant and the motor design has been based on maximising efficiency at the expense of size.
Propulsion Motor Fans
The GEC article extensively describes the 2400 propulsion motor ventilation, that consists of two substantial Series DC Motor driven fans and four outlets, as one would expect each outlet passes through a water - cooled heater exchanger Fig 1b. As the control on occasion, requires only one fan running, shutters prevent air passing the fan duct of the fan that is shut down. It would seem complex control has been avoided by supplying the fan with the same voltage as the armatures, thus anticipating the prospective losses generated within the motor in any given propulsion speed range. Particularly when submerged on battery. In some circumstances, with fans shut down completely. The performance of motors with the main field in series with the armature, is significant in the efficient control of the motor ventilation. Further detail is beyond the scope of this article.
In the old submarines like the preserved Alliance, each fan (one per propulsion motor) is driven by a compound DC motor controlled by a manual three step controller, set to suit the propulsion conditions by the Watch Keeper. Quite often run at speeds higher than strictly needed, creating unnecessary electrical losses that had to be supplied by the battery.
The large journal bearings of the main motor, have oil pumped into them prior to starting, the normal practice for machines of this size. The lube oil pumps are fixed to each end of the main motor frame and appear have an electric motor of about 7.5hp. The bearings are also designed to cope with the movement of the submarine and shock. This shock would not be underestimated as there are WW2 reports of motor and engines being lifted off their beds while being depth charged.
R Pratt - Conclusion
R Pratt, the author concludes by stating:
following the above design study (commenced 1979), a large double-armature single screw propulsion unit was designed and constructed by GEC Alsthom Large Machines Ltd and fitted in the submarine that was expected to be commissioned soon.
In fact it was commissioned (Royal Navy) 2 June 1990 as HMS Upholder and proved to be a successful overall design once the 'bugs' were experienced and removed, with no failures related to the quality and design the GEC Main Motor.
Media Reported Electrical flash-over Failure during 'Crash Reversal' exercise
One event is often reported in the technical media of today - that in a trial emergency astern manoeuvre, a flash-over and short circuit of the maximum available short current from the batteries occurred, due to make before break switching failure due to faulty software. The anecdotes that follow give good reason to believe, this was not the complete description of the failure. They also demonstrate the vital ability of the submarine to retain useful propulsive power with one armature system out of service on this single shaft vessel.
- Contact was made with the Navigating Officer who was aboard Upholder at the time. He holds an engineering degree and from his comments it is clear that the converter for the shunt field of one of the dual armatures, did not function and thus this armature did not act as normal and generate a back EMF, essential to oppose the battery voltage thus moderating the armature current. The author believes that then the quite complex brush gear contacting the copper commutator of the effected armature, without shunt field current (see earlier image of the motor) failed due to the excessive current and a complete battery short circuit developed. I was reliably informed that the Upholder returned to base without the need to be towed, therefore the other armature of the dual armature motor, was not involved in the incident and was supplied as normal with field current by it's own converter and not effected by the fault. A harbour trial was carried out with a load rotor fitted instead of the normal screw and the same fault occurred. The cause was located and no failures of this type have occurred since.
- Contact was also made with another person, who was also on Upholder at this time, here is his account of the event:
Recollections of an old member of the engineering branch
Upholder was conducting 'crash reversal' trials at safe depth. The Chief Tiff was looking through the inspection ports and as I had just past my 'Operators Board' this was my first official watch by myself. During on the crash reversals the Chief Tiff had noticed some sparking around the main motor, so he moved to another position to get a clearer view.
During that process the decision had been made to conduct another (think it was B-I-S) run. The speed was brought up via the Optical encoder from Group Up (as you can vary the speed through an optical decoder either at the OMC (Primary) or at the Propulsion Switchboard (Secondary)). The idea being that to help prevent cavitation the optical encoder was used at the 'half' position and was used to increase speed up to the full position.
Anyway back to 'the dit'
As they were attempting the next crash reversal, The Chief Tiff observed severe sparking around the Fwd Armature and shouted to me to stop the main motor. As you are aware you're not directly allowed to take propulsion away from the 'old man' so I piped 'Stop the Main Motor' – just as I did the battery tried to 'discharge' over the main motor. There was a massive flash, (still believe my imprint is located at the MCC) coupled with the obligatory bang. During this process the battery voltage lowered and as a consequence the 140kw MGs 'sensed' a loss of dc and tripped on under voltage. As a result the submarine was left in the dark for several minutes until the MG's had run down and it was safe to re-start them.
We surfaced and ran on single armature to Campbelltown where repairs were conducted the mishap was investigated. The Submarine then proceeded back to Barrow for a more thorough investigation.
There are no reports of a failure like this ever occurring again.
A Diesel Electric Submarine Propulsion Simulation
Dr Buxton also sent a paper A Diesel Electric Submarine Propulsion Simulation by Lt Commander M A Bowker, BSc, MSc, RN and Commander N A Hainses, BSc, MSc, RN. The purpose of the paper was to outline computer based simulation of a typical submarines propulsion system, with particular emphasis on snorting - the importance to this article was that the 2400 was the basis for the paper and though quite technical, it goes some way to explaining to those of us not familiar with modern thinking, the operating techniques to obtain the maximum range snorting in various circumstances.
One point of particular interest was that proceeding with the batteries in series and the armatures in parallel, was electrically more efficient than the conventional batteries in parallel when the armatures were in series, the lower speed range, group down.
It was interesting to note the authors also stated that the Slow speed Motor Generator, was of the Ward-Leonard style - and as stated earlier in Part 1, an old, but very effective method of controlling a DC supply for a special purpose.
That these submarines have apparently been plagued with problems in the RCN, has been well reported elsewhere, but this is not the concern of this article, that focuses on the electrical propulsion of the submarine that apart, from a major short circuit during an emergency reverse in the early trials in RN service, seems to have performed reliably in the RN without the need for major repair or alteration.
Unlike the earlier now decommissioned T Class conversion and the P Class & O Class, there had not been the benefit a detailed manual or speed trial document, to base an article of reasonable technical accuracy about the Electrical Propulsion of the Victoria Class, but having received some helpful information (shown in Part 1), a review of the GEC Machines article (part 2), combined with personal experience with earlier submarines, the author felt a sensible article could be put together based on a diagram postulating the detail of the motor control circuitry. This has been the case
|Excellent article. However the account of the flashover is slightly incorrect. I was the person looking into the Main Motor during the BIS crash reversal. (VSEL Commissioning Engr, it wasn't a "tiff"). I still have the hand-written reports of the incident (and the T-shirt!). As I recall, we propelled slowly back to Faslane on the aft armature only. She was then towed back to Barrow where modifications were made to the Starters, Groupers and Main Motor Breakers. The whole lot went up in another bang and a flash as Ship's Staff selected BIS (MMBs open) with shore supply connected just before leaving to continue with CSTs. That magnetised the hull which had to be demag'd at a cost, I believe, of £4M. Upholder/Chicoutimi has had an interesting history ;)