POWER TRAIN CONTROLS AND CONNECTIONS FOR AUXILIARY VESSELS

Abstract: The invention relates to power trains for auxiliary marine vessels such as tug boats. Prior power trains for such vessels lacked flexibility of operation, control, location, and were not as efficient as they could have been. In order to solve this problem power control units are used to control direct current drive motors which are used to power the propellers. Diesel motors (10) are used to drive alternating current generators. The output from these generators is supplied to direct current motors (20) which drive the propellers (24) of the vessel. The direct current motors (20) are controlled by silicone control rectifiers (17) and variable current controls (18). An additional benefit of the use of such a power train is that the diesel motors (10) may be located in the forward part of the vessel and the direct current motors (20) may be located in the aft part of the vessel for trim purposes and to shorten the propeller shaft. Benefits of this power train when used on auxiliary vessels are economy of fuel and space.

Description: -1- Description Power Train Controls and Connections for Auxiliary Vessel Technical Field The invention relates generally to power trains for powering auxiliary marine vessels, and more particularly to diesel-electric power trains having silicon voltage control rectifiers for vessels subject to a wide range of loads, uses and space limitations. In the prior art, power trains for the purposes note lacked flexibility of operation and control, and within such limitations often operated at less than maximum effi iency. Background Art The prior art " , West German Patent No. 2,316,423, pro vided for a power producing unit comprising an electrical generating means for producing a constant alternating cur cent voltage, and power control units connected in series with the rotor coil of a shunt wound direct current motor means. Power control units are silicon rectifiers which rectify the alternating current voltage from the generati means. United States Patent No. 1, 861,750 provided for plurality of generators powered by diesel engines, the po producing units being parallel, and a plurality of motors in parallel with each other, but in series with the field coil of a direct current motor for rectifying and control ling current to the coil. United States Patent No. 3,148, 318, provided for using a rotor control to control motor speed for base revolutions per minute of 100% and less, a field coil controls to control motor speed for base revol¬ utions per minute of above 100%. United States Patent No. 3,351,830, provided for two motors driving one output sha through a gear box. " RE Disclosure of Invention In accordance with the present invention, there is provided a power train for auxiliary marine vessels that is .controllable by a plurality of power control units in forward and reverse directions from zero to maximum revol¬ utions per minute. There is also provided a power train as stated above comprising a plurality of power producing and power using units that have respectively different performance charact- eristics that are complementary to supply a variety of loads at respectively maximum unit efficiency. There is also provided a standby for each power pro¬ ducing, using and control unit to prevent a failure of one from interferring with the flexibility and control for the full- efficient use of said power train. There is also provided a power train that is suscept- able to division for an installation of maximum convenience and space saving. There is also provided a method of complementing the maximum advantages of power producing and power using units and eliminating the respective disadvantages of both. Brief Description of Drawings The details of the invention will be described in connection with the accompanying drawings, in which figure 1 is a schematic diagram of a typical power train according to the invention; figure 2 is a graph of a typical diesel engine performance curve; figure 3 is a graph of the per¬ formance curve of a shunt wound direct current motor; figure 4 is a graph of a propeller revolution per minute curve and vessel speed curve for a towing tug having a conventional reduction gear drive; figure 5 is a graph similar to figure 4 but with the tug free running with not tow, and with in¬ vention drive data comparably entered; figure 6 is a graph IU REΛTΓ OMP showing fuel consumption of a typical diesel engine run¬ ning at rated revolutions per minute; figure 7 is a graph similar to figure 5 comparing a two diesel reduction gear drive with two and three diesel electric drives according to the invention. Best Mode for Carrying Out the Invention Referring to figure 1, a typical power train 9 of the invention comprises two main diesel motors - alter¬ nating current generator units, or power producing units 10, connected in parallel and to a smaller auxiliary diesel motor - alternating current generator, or power producing unit 12, through a transformer 14. A third diesel motor alternating current generator, or power producing unit 10', shown in phantom, may be added to the power train if desired. The output of power producing units 10 is rectified and voltage controlled by power control units 16 comprising four silicon rectifiers 17 and four variable current con¬ trols 18. • The silicon control rectifiers 17 are connected through magnetic contacts 19 to shunt wound direct current motors, orpower using units 20. Current through the shunt field windings 21 is regulated by said current controls 18 mounted between the output of said power producing units 10 and said field windings or coil 21. Main propulsion motor 20 respectively receive the output of a power control unit 16, the propulsion motors being mounted in pairs to drive respective main propellers and propeller shafts 24, either singly or jointly, through respectively common gear boxes 26. Single motors 20 are provided to drive main auxiliaries such as a bow thruster 28 and a tow winch 30, respectively. These motors are connected, each alternatively to a pair of silicon control rectifiers 17 and each to a variable current control 18 to provide standbys in case of a failure of one. OMPI Wlp < Referring to figure 2, the performance characteris¬ tics of a diesel engine is shown to be that torque and horsepower rises with revolutions per minute until a maximum for all three is reached. Since the diesel of t disclosure cannot safely be run above 900 revolutions pe minute, the torque and horsepower at this speed is maxi at 100%. Referring to figure 3, the performance charact istics of a shunt wound motor is shown to be that torque is constant at 100% from zero through 100% of base revol utions per minute to maximum at 100% of the base revolut ions per minute as voltage to motor is increased. There after revolutions per minute can be increased up to 200% of the base revolutions .per minute without damage by reducing shunt field current. In this mode, horsepower remains constant at 100% and the torque varies downward shown in figure 3. Referring now to figure 4, a tug and tow performanc curve shows that the 5578 shaft horsepower, the tug and tow will make 10.7 knots with propeller speed of 145.7 revolutions per minute. Now referring to figure 5, it i seen that when running free, the tug of figure 4 is limi by its gear reduction drive to a propeller speed of 150 revolutions per minute to use only 3330 shaft horsepower the 5578 shaft horsepower available to make 14.63 knots. It is seen in comparison, that thei electric drive of the invention with one engine of 2600 shaft horsepower can drive the tug 13.9 knots with both propellers at a speed of 140 revolutions per minute using all available shaft horsepower, which is only .73 knots less than the reduct ion gear drive does with two engines. If two engines ar used in the electric drive of the invention which can in crease its motor, shaft and propeller speeds without dam by reducing the motor field current, it is seen that at revolutions per minute all available 5200 shaft horsepow is used to drive the tug 15.7 knots. Referring now to figure 6, the fuel consumption curve of a diesel engine shows that fuel consumption per brake horsepower hour decreases as the load increases to its rated capacity. Thus in the case of figure 5 for the gear reduction drive tug, only 3400 brake horsepower of the.5750 available is used, that is about 60% for a fuel consumption rate of .409 pounds per brake horsepower hour, or 197.2 gallons per hour. Whereas the invention using one engine utilizes the full 2875 brake horsepower available to con- sume only .392 pounds per brake horsepower hour, or 158.3 gallons per hour. In free running, the electric drive of the invention will use 734 gallons of fuel per day less to travel the same distance, that is a savings of about 18%. Even if -the power train of the invention has about 10% loss against 3% loss in the gear reduction drive power train, or a net loss of 7%, nevertheless there is a fuel economy gain of 18%, plus half the lubricating oil and half the engine time expended for 8% slower time for the trip. Referring to figure 7, a further comparison is made as in figure 5, but with diesel engines of lesser brake horse¬ power in two and three engine installations. In addition to economy of operation, the power train of the invention lends itself to a further economy in the use of limited space available on an auxiliary marine vessel. Thus power producing units may be mounted forward to better trim the vessel without an addition of ballast when loaded or working, and the power using units may be mounted aft to shorten porpeller shafts and save the space required by longer ones. Power control units may be mounted wherever convenient, their mass and occupied space being negligible. It should be understood that the invention can be separately and jointly connected in any arrangement in number and function so that power using units can be run independently of each other off one power producing unit through one or more power control units, or vice versa.

Claims: Clai s 1. Apparatus for interconnecting and controlling .units-o a power train for maximum flexibility and economy in the operation of auxiliary marine vessels having pro- • pellers and propeller shafts driven thereby, and com¬ prising in combination: a plurality of power producin unit means connected in parallel, each comprising ele trical generating means for producing a constant volt age and frequency alternating current, and diesel eng means for producing maximum torque and brake horsepow at maximum rated revolutions per minute with minimum fuel consumption per brake horsepower hour for drivin said electrical generating means; a plurality of powe control unit means connected in parallel with each ot and respectively in series with said power producing unit and comprising a plurality of silicon control re tifier means for rectifying and voltage controlling t constant voltage and frequency output of said electri cal generating means into variable voltage direct cur rent, and a plurality of electrical current control means connected in parallel with each other and in series with said electrical generating means for rec¬ tifying and varying the current; and a plurality of shunt wound direct current motor means having rotor coils and field coils, said rotor coils for connectin together in parallel, and to the silicon control rec¬ tifier means in series with said power producing unit means for activation and control of varying speeds of said direct current motor means below 100% of base revolutions per minute, said field coils being connec ed in series through said electrical current control means with said electrical generating means and in parallel with each other for activating said direct current means in combination with said silicon contro -βUR OM . Λ, rectified means and controlling said varying speeds above said 100% of base revolutions per minute of said direct current motor means. 2. Apparatus as described in claim 1 wherein a pair of said plurality of direct current motor means are mounted to jointly and severally drive each of said propellers and propeller shafts through a common gear box, the shunt wound field coils of said pair of direct current motor means being connected in series to current controlled direct current, and the rotor coils to voltage controlled direct current. 3. Apparatus as described in claim 1 wherein at least one of said plurality of shunt wound direct current motor means is for driving auxiliary equipment, and its rotor coil is connected alternatively to the silicon control rectifier means of a pair of said plurality of direct current motor means, and its field coil is connected to an independent current control means. 4. Apparatus as described in claim 1 wherein said plural¬ ity of ' power producing unit means are mounted forwardly in said auxiliary marine vessel for substantially trim¬ ming said vessel when loaded and working without the use of ballast and the loss of space therefor. 5. Apparatus as described in claim 1 wherein said plurality of power using unit means are mounted aft in said aux- iliary marine vessel for minimizing the length of said propeller shafts and the space required for said shafts. 6. Method of interconnecting and controlling units of a power train mounted in an auxiliary marine vessel for • complementing the maximum efficiency operating charac eristics of each unit with the other units for maximu operating efficiency of the combination, comprising t steps of: mounting diesel engine means having limite speed control and adapted to drive fully loaded at maximum rated speed a constant speed alternating curr generator for an output of constant voltage and fre- quency alternating current with minimum fuel consumpt connecting power control units to said constant volta and frequency alternating current output, said power control units having silicon control rectifier means for rectifying some o£ said alternating current outpu mounting shunt wound direct current motors having per formance characteristics of constant maximum torque up to maximum rated revolution ' per minute and maximum constant shaft horsepower t erebeyond; and connecting said shunt wound direct current motor to the output of said power control units for controlling the revol utions per minute of said power using units to fully load said diesel engine means for delivering and usin maximum engine per brake horsepower hour.

Inventors: OBRIEN H
Applicants: OBRIEN H
Application year: 1978
Main classification: B63B9
IPC codes: B63H21, B63H23, F02B3