Marine propulsion system

• US 4,338,525 A
• Filed: 01/05/1981
• Issued: 07/06/1982
• Est. Priority Date: 01/05/1981
• Status: Expired due to Fees

• Current Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Kilgore, Lee A.
• Primary Examiner(s): Dobeck, B.
• Assistant Examiner(s): Wade, Shelley
• Application Number:
  US06/222,457
• Time in Patent Office: 547 Days
• Field of Search: 318/723, 318/148, 290/17, 290/14
• US Class Current: 290/17
• CPC Class Codes: B60L 2220/12 Induction machines
• CPC Class Codes: B60L 2220/14 Synchronous machines
• CPC Class Codes: B60L 50/13 using AC generators and AC motors
• CPC Class Codes: H02P 1/52 by progressive increase of frequency of supply to motor
• CPC Class Codes: H02P 3/24 by applying dc to the motor
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors

Abstract

A marine propulson system is described that includes a gas turbine, an alternating current generator, a fixed pitch propeller, a synchronous motor and a frequency converter. The frequency converted is connected electrically between the generator and motor during starting and reversal procedures when the motor would normally have to operate as an induction motor. Means are provided to brake the system dynamically to speeds within the capacity of the frequency converter. At speeds within the frequency converter'"'"'s design capacity, the motor can be operated synchronously while it is running at a speed below the minimum operating speed of the turbine and generator.

Claims

1. A marine propulsion system comprising:

a prime mover;

means for controlling the speed of said prime mover;

an alternating-current generator, said generator connected to and driven by said prime mover;

a synchronous motor electrically connectable to an output of said generator;

a fixed pitch marine propeller connected to an output of said motor;

a solid state frequency converter whose input is the frequency of said generator and whose output is a lower frequency which is electrically connectable to said synchronous motor, said frequency converter being capable of maintaining said synchronous motor in synchronous operation when said motor is operating at a speed below that of said generator, said frequency converter being capable of supplying torque to said motor when the rotor of said motor is stationary;

a braking means;

switchgear means for electrically connecting said generator electrically to said motor; and

switchgear means for electrically connecting the output of said frequency converter to and between said generator and said motor.

2. The marine propulsion system of claim 1, wherein:

said braking means comprises an electrical resistor connectable to said motor.

3. The marine propulsion system of claim 1, wherein:

said alternating-current generator is of the three-phase type.

4. The marine propulsion system of claim 3, further comprising:

means for reversing two of the electrical phases of the alternating-current input to said motor.

5. The marine propulsion system of claim 1, wherein:

said prime mover comprises a gas turbine engine.

6. A ship propulsion system, comprising:

a prime mover;

means for controlling the speed of said prime mover;

a three-phase alternating-current generator connected to said prime mover;

a synchronous motor;

a solid state frequency converter connected electrically to said generator and capable of converting the frequency of said generator to any preselected frequency in the range from zero to the minimum operating frequency of said generator, said frequency converter being connectable to said motor and being capable of supplying torque to said motor throughout said range of frequencies;

a marine propeller mechanically connected to said synchronous motor;

means for electrically connecting and disconnecting said synchronous motor to the output of said frequency converter;

means for electrically connecting and disconnecting said synchronous motor to said generator;

means for reversing the electrical phase relationship of said generator;

a braking means capable of slowing the rotational speed of the rotor of said synchronous motor; and

whereby said synchronous motor is maintained in synchronous operation throughout its complete range of speeds both forward and reverse.

7. A method of initiating motion of a stationary marine vessel whose propulsion system comprises a prime mover, an alternating-current electrical generator, a frequency converter, a synchronous motor and a fixed pitch propeller, said method comprising:

operating the prime mover at its minimum speed;

electrically connecting the frequency converter in series with and between the generator and the synchronous motor with the output of the frequency converter connected electrically to the synchronous motor;

increasing the output of the frequency converter from near zero to the desired running speed of the motor; and

electrically connecting the output of the generator directly to the motor and electrically disconnecting the frequency converter from the motor when the speed of the motor approaches the output capacity of the frequency converter.

8. A method for stopping the motion of a moving naval vessel whose propulsion system comprises a prime mover, an alternating-current electrical generator, a frequency converter, a synchronous motor and a fixed pitch propeller, said method comprising:

discontinuing the supply of fuel to the prime mover;

connecting a braking means to the propulsion system;

electrically connecting the frequency converter in series with and between the generator and the motor when the speed of the motor has decreased to a value within the operational range of the frequency converter;

decreasing the output of the frequency converter to the motor to zero;

reversing the phasing sequence of the frequency converter'"'"'s output to the motor; and

increasing the phase reversed output of the frequency converter to the motor.

9. The method of claim 8, further comprising:

decreasing the phase reversed output of the frequency converter to the motor as the naval vessel'"'"'s speed decreases to zero.