Prime-mover dynamo plants – Plural prime mover – Plural prime movers with fluid interconnection
Reexamination Certificate
1999-01-20
2001-02-13
Enad, Elvin (Department: 2834)
Prime-mover dynamo plants
Plural prime mover
Plural prime movers with fluid interconnection
C290S00400D, C290S00400D, C290S00400D, C290S00400D
Reexamination Certificate
active
06188139
ABSTRACT:
BACKGROUND OF INVENTION
This invention relates to integrated marine power distribution arrangements and, more particularly, to such arrangements that provide electric power at frequencies higher than the usual 60 Hz.
Conventional integrated marine electric drive systems generate AC power at 60 Hz and either utilize the AC power directly at 60 Hz, through frequency converters for the ship's propulsion motors and transformers for the ship's auxiliary power circuits, or rectify the AC power from the generator and distribute direct current (DC) power and then convert the DC power to AC power using conversion equipment for the ship's propulsion motors and also for the ship's auxiliary power circuits.
The Satterthwaite et al. U.S. Pat. No. 4,661,714 discloses an integrated marine propulsion system that produces AC power at a frequency two to three times the standard low voltage, 480 VAC, 60 Hz frequency, i.e., up to 180 Hz. The outputs of the AC power generators are supplied through a ship service switchboard to a series of frequency converters that supply the propulsion motors for the ship at frequencies that vary from 0 to 60 Hz. In addition, the switchboard supplies the higher frequency power to a transformer and frequency converter that produce the ship's service utility and auxiliary power at standard 60 Hz frequency.
The Levedahl U.S. Pat. No. 5,684,690 discloses an integrated electrical power supply system for propulsion and service power in a ship in which two alternators, a propulsion alternator and a separate service alternator, are powered from the same turbine or engine. The frequency of the power generation is not disclosed. In this arrangement, the use of added multiple generators in parallel is not practical.
The Dade et al. U.S. Pat. No. 5,199,192 discloses an electric power system for marine vehicles in which one or more AC generators supply both ship's propulsion and ship's service auxiliaries. The output from the generators is rectified to a DC voltage for distribution and reconverted to AC for the propulsion motors and also for ship service. There is no provision for an integrated electric plant whereby multiple generators are paralleled for maximum efficiency.
In the prior art, integrated electric plants with limitations of frequency, voltage, and generator arrangements are presented. Such integrated electric power systems have certain disadvantages with respect to size and weight that have not been heretofore addressed.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an integrated electric propulsion and distribution arrangement providing maximum power density that overcomes disadvantages of the prior art.
Another object of the invention is to provide an integrated electric propulsion and power distribution arrangement producing optimum engine/turbine prime mover speed that provides the highest power density and uses the lowest weight engine.
A further object of the invention is to provide an integrated power distribution system having a generator with the optimum generator pole pair configuration that produces the highest power density and uses the lowest weight generator.
An additional object of the invention is to provide an integrated high power distribution arrangement for converting power from low voltage (450 VAC) to a medium voltage (15 kV) level, at frequencies greater than 60 Hz.
Another object of the invention is to provide a power distribution arrangement having transformer isolation and low system harmonics while maintaining a high power density.
A further object of the invention is to provide a power distribution arrangement utilizing the same multiple power modular power conversion equipment for the ship propulsion motor and the ship service power conversion equipment.
These and other objects of the invention are attained by providing an integrated power distribution supply utilizing prime movers and generators operating at higher speed and/or having a higher number of poles to produce power at higher distribution frequencies.
In accordance with the invention, a prime mover may be any higher speed gas or steam turbine, or diesel engine. Typically, a steam turbine operating at 7,500 RPM will provide a weight savings of approximately 50% over one operating at 3,600 RPM which produces the same power. In addition, generator weights can be reduced as the number of generator poles and the generator operating speed is increased. As an example, where generator speed is increased from 3,600 RPM to 7,500 RPM and the number of generator poles is increased from 2 to 4, a weight saving of approximately 50% can be obtained. An 1,800 RPM, 4 pole, 60 Hz generator typically weighs 72,500 lbs. which is excessive when compared to a 7,000 RPM, 4 pole, 233 Hz generator at the same power rating which weighs approximately 34,000 lbs. and has more than twice the power density. This increased power density and corresponding weight reduction allows the prime mover and generator to be located higher in the ship without adversely affecting ship stability. The corresponding decrease in the length and size of intake and exhaust ducts for gas turbine and diesel engine applications further reduces the weight and volume of the arrangement.
To accomplish such an increase in power density, the generator is driven by the prime mover at a speed to produce its rated voltage but at frequencies above 60 Hz and up to 400 Hz. The generator voltage can be any standard marine distribution voltage from low voltage (450 VAC) to medium voltage (15 kV). In addition, the higher system frequencies (>60 Hz to 400 Hz) enables further weight savings in other components and enhanced system performance.
For ship propulsion, the higher than 60 Hz distribution frequency is converted to the required ship propulsion motor frequency using conventional frequency conversion equipment. The propulsion motor may thus be coupled directly to a propeller shaft having a fixed pitch propeller.
For ship service power, the higher than 60 Hz distribution frequency is converted to the required service distribution system frequency using conventional frequency conversion equipment The ship service system can be arranged to supply DC power, standard 60 Hz AC power or AC power at any variable voltage and frequency.
The higher distribution frequency of the arrangement according to the invention allows the power conversion equipment connected to the main distribution bus to utilize a power-dense design. Transformer size and weight are minimized with higher frequencies allowing a smaller core design. In addition the power conversion equipment based on pulse width modulation PWM technology at higher modulation frequencies can reduce filtering.
REFERENCES:
patent: 4114555 (1978-09-01), O'Brien, Jr.
patent: 4645940 (1987-02-01), Wertheim
patent: 4709203 (1987-11-01), Roux et al.
patent: 4927329 (1990-05-01), Kliman et al.
patent: 4967097 (1990-10-01), Mehl
patent: 5038265 (1991-08-01), Paladel
patent: 5109185 (1992-04-01), Ball
patent: 5194757 (1993-03-01), Wertheim
patent: 5199912 (1993-04-01), Dade et al.
patent: 5222901 (1993-06-01), Burkenpas
patent: 5301096 (1994-04-01), Klontz et al.
patent: 5373433 (1994-12-01), Thomas
patent: 5519275 (1996-05-01), Scott et al.
patent: 5684690 (1997-11-01), Levedahl
Adair Robert M.
Castles Gene
Rinaldi Peter M.
Thaxton Edgar S.
BakerBotts L.L.P.
Electric Boat Corporation
Enad Elvin
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