Method for starting a fuel cell system and fuel cell system

• US 6,612,385 B1
• Filed: 10/17/2000
• Issued: 09/02/2003
• Est. Priority Date: 04/17/1998
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Stühler, Walter, Weiss, Alfred
• Primary Examiner(s): Rice, Kenneth R.
• Assistant Examiner(s): McClellan, James S.
• Application Number:
  US09/690,299
• Time in Patent Office: 1,050 Days
• Field of Search: 180/65.1, 180/65.2, 180/65.3, 429/12, 429/13, 429/19, 429/23
• US Class Current: 180/65.31
• CPC Class Codes: B60L 58/31 for starting of fuel cells
• CPC Class Codes: H01M 8/04225 during start-up
• CPC Class Codes: H01M 8/04302 applied during start-up
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

A method for starting a mobile fuel cell system, in particular for a vehicle, includes conveying air to be supplied to the system during starting and operation of the system by a motor-powered compressor, in order to ensure a necessary operating pressure and, if required, additional humidifying of the air. A motor drive for the compressor has an electric motor which is supplied from a mobile starter battery during a starting phase. An output voltage of the starter battery is different from an operating voltage at an output of a fuel cell stack of the fuel cell system. A control device is provided between an output of the starter battery or of the fuel cell stack and a motor input. The control device interrupts the starting voltage supplied from the output of the starter battery and switches over to the output voltage of the fuel cell stack when the output operating voltage of the fuel cell stack reaches an adequate level. A fuel cell system is also provided.

Claims

1. A method for starting a fuel cell system, which comprises:

providing a fuel cell stack;

supplying a working medium to the fuel cell stack with a compressor;

driving the compressor with an electric motor having a first winding system constructed for a voltage of a starter battery and a separate second winding system constructed for an operating voltage of the fuel cell stack;

initially feeding the electric motor with current from the starter battery, then feeding the electric motor with current from the fuel cell stack with the first winding system electrically disconnected from the fuel cell stack; and

providing a control device having a converter for controlling the feeding of the current to the electric motor.

2. The method according to claim 1, which further comprises providing a mobile air and hydrogen system as the fuel cell system, supplying the fuel cell system with air as the working medium during starting and operation, and conveying the air by the motor-driven compressor to ensure a necessary operating pressure and additional humidifying of the air.

3. The method according to claim 1, which further comprises supplying the electric motor driving the compressor from the starter battery during a starting phase of the fuel cell system.

4. The method according to claim 1, which further comprises setting a voltage of the starter battery to be different from an operating voltage of the fuel cell stack.

5. The method according to claim 1, which further comprises providing a control device between an input of the electric motor and at least one of an output of the starter battery and an output of the fuel cell stack, and interrupting a starting voltage supplied from the output of the starter battery and connecting an output voltage of the fuel cell stack to the electric motor, with the control device, when the fuel cell stack reaches an adequate output voltage.

6. The method according to claim 5, which further comprises providing the control device with a converter, setting an operating voltage of the electric motor to correspond to a voltage of the starter battery, and regulating the output voltage of the fuel cell stack with the converter down to at least a value of the operating voltage of the electric motor.

7. The method according to claim 6, which further comprises permanently regulating a rotational speed of the electric motor with the converter.

8. The method according to claim 6, which further comprises providing a direct-current controller as the converter, and providing a direct-current motor as the electric motor.

9. The method according to claim 5, which further comprises providing a converter having an intermediate circuit with components as the control device, and continuously increasing the operating voltage at the output of the fuel cell stack, for raising the components in the intermediate circuit of the converter to a higher operating voltage.

10. The method according to claim 1, which further comprises switching over the fuel cell system from the starter battery to the fuel cell stack as soon as an output voltage of the fuel cell stack is higher than a voltage of the starter battery.

11. The method according to claim 1, which further comprises setting an operating voltage of the fuel cell stack to be approximately twice as great as a voltage of the starter battery.

12. The method according to claim 1, which further comprises selecting an inverter as the converter.

13. The method according to claim 1, which further comprises permanently connecting the electric motor to an output of the converter, permanently connecting the second winding system, constructed for the operating voltage of the fuel cell stack, to the output of the converter, and isolating the first winding system, constructed for the voltage of the starter battery, from the fuel cell stack and the starter battery as voltage sources, through disconnection elements.

14. The method according to claim 13, which further comprises disconnecting the first winding system of the electric motor at a zero crossing.

15. The method according to claim 1, which further comprises drawing current from the starter battery only until an output voltage of the fuel cell stack has reached a value greater than a voltage of the starter battery.

16. The method according to claim 1, which further comprises providing the electric motor as a synchronous motor.

17. The method according to claim 1, which further comprises providing the electric motor as an asynchronous motor.

18. A fuel cell system, comprising:

a starter battery;

a fuel cell stack;

a compressor for supplying a working medium to said fuel cell stack; and

an electric motor for driving said compressor, said electric motor to be selectively operated with only current from said starter battery and with only current from said fuel cell stack.

19. The fuel cell system according to claim 18, wherein said starter battery and said fuel cell stack have outputs, said electric motor has an input, and an electronic control device with a converter is to be connected between said input of said electric motor and said outputs of said starter battery and said fuel cell stack.

20. The fuel cell system according to claim 19, wherein said converter has an input, and a switching apparatus is connected electrically upstream of said input of said converter.

21. The fuel cell system according to claim 20, wherein said switching apparatus has inputs connected to said starter battery and to said fuel cell stack to be switched over smoothly.

22. The fuel cell system according to claim 19, wherein said converter has an output permanently connected to said input of said electric motor.

23. The fuel cell system according to claim 18, wherein said electric motor is a synchronous or asynchronous motor having a first winding system constructed to be supplied with a low voltage and a separate second winding system constructed to be supplied with a higher voltage.

24. The fuel cell system according to claim 23, wherein said starter battery and said fuel cell stack have outputs, a converter has an input, and decoupling diodes permanently connect said outputs of said starter battery and said fuel cell stack to said input of said converter.

25. The fuel cell system according to claim 23, wherein said first winding constructed for low voltage is to be disconnected.

26. The fuel cell system according to claim 25, including disconnection elements integrated in said electric motor.

27. A mobile fuel cell system to be operated with air and hydrogen for a vehicle propulsion system, comprising:

a starter battery;

a fuel cell stack having a number of fuel cells, an inlet for hydrogen and an inlet for compressed air;

a compressor connected to said air inlet for supplying a working medium to said fuel cell stack; and

an electric motor for driving said compressor, said electric motor to be selectively operated with only current from said starter battery and with only current from said fuel cell stack.