Electric powertrain system having bidirectional DC generator

• US 20080265812A1
• Filed: 04/30/2007
• Published: 10/30/2008
• Est. Priority Date: 04/30/2007
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Adra, Rodwan Tarek
• Granted Patent: US 7,812,555 B2
• Time in Patent Office: Days
• US Class Current: 318/375
• CPC Class Codes: B60L 2210/20 AC to AC converters
• CPC Class Codes: B60L 2220/18 Reluctance machines
• CPC Class Codes: B60L 50/11 using DC generators and DC motors
• 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
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

An electric powertrain for use with an engine and a traction device is disclosed. The electric powertrain has a DC motor/generator operable to receive at least a portion of a first mechanical output from the engine and produce a DC power output. The DC motor/generator is also operable to receive DC power and produce a second mechanical output. The electric powertrain further has a drivetrain operable to receive the DC power output and use the DC power output to drive the traction device. The drivetrain is also operable to generate DC power when the traction device is operated in a dynamic braking mode.

Claims

1. An electric powertrain for use with an engine and a traction device, comprising:

a DC motor/generator operable to;

receive at least a portion of a first mechanical output from the engine and produce a DC power output; and

receive DC power and produce a second mechanical output; and

a drivetrain operable to;

receive the DC power output and use the DC power output to drive the traction device; and

generate DC power when the traction device is operated in a dynamic braking mode.

2. The electric powertrain of claim 1, further including a braking grid operable to dissipate as heat a portion of the DC power generated by the drivetrain.

3. The electric powertrain of claim 2, further including a chopper operable to control an amount of DC power dissipated by the braking grid.

4. The electric powertrain of claim 1, wherein the drivetrain includes at least one DC traction motor operable to act as a DC motor and a DC generator.

5. The electric powertrain of claim 1, wherein the drivetrain includes:

at least one AC traction motor operable to act as an AC motor and an AC generator; and

a bidirectional power converter coupled with the at least one AC traction motor, the bidirectional power converter being operable to act as an inverter and a rectifier.

6. The electric powertrain of claim 1, further including:

an AC alternator operable to receive a portion of the first mechanical output and produce an AC power output; and

a rectifier coupled with the AC alternator, the rectifier being operable to convert the AC power output to a DC power output combinable with the DC power output of the DC motor/generator.

7. The electric powertrain of claim 6, further including a controller operable to:

set the DC motor/generator to act as a DC motor;

set the DC motor/generator to act as a DC generator; and

block a current from flowing from the rectifier to the AC alternator.

8. The electric powertrain of claim 6, wherein:

the engine is rated to produce a first amount of mechanical power and to receive a second amount of mechanical power, the second amount of mechanical power being less than the first amount of mechanical power;

the DC motor/generator is sized based on the second amount of mechanical power; and

the AC alternator is sized based on a difference between the first and second amounts of mechanical power.

9. The electric powertrain of claim 8, wherein the AC alternator is further sized based on a frequency of the portion of the first mechanical output delivered to the AC alternator.

10. The electric powertrain of claim 1, wherein:

the engine is rated to produce a maximum amount of mechanical power; and

the DC motor/generator is sized based on the maximum amount of mechanical power.

11. The electric powertrain of claim 1, further including a controller operable to:

set the DC motor/generator to act as a DC motor; and

set the DC motor/generator to act as a DC generator.

12. The electric powertrain of claim 1, further including a connection to an off-board DC power source, the connection operable to receive DC power from the off-board DC power source to supplement the generated DC power.

13. The electric powertrain of claim 12, wherein the DC motor/generator is further operable to convert at least a portion of the DC power received from the off-board DC power source to at least a portion of the second mechanical power output.

14. A method of operating a machine, comprising:

combusting fuel to generate a first mechanical power output;

converting the first mechanical power output to a first DC power output;

using the first DC power output to propel the machine;

converting a motion of the machine to a second DC power output; and

converting the second DC power output to a second mechanical power output, wherein the second mechanical power output minimizes an amount of fuel combusted.

15. The method of claim 14, further including dissipating as heat a portion of the second DC power output.

16. The method of claim 14, wherein the step of converting the first mechanical power output includes converting a portion of the mechanical power output to an AC power output and converting the AC power output to a portion of the first DC power output.

17. The method of claim 14, wherein:

the step of using the first DC power output includes converting the first DC power output to a first AC power output; and

the step of converting a motion of the machine to a second DC power output includes generating a second AC power output and converting the second AC power output to the second DC power output.

18. The method of claim 14, further including:

receiving a third DC power output;

using a first portion of the third DC power output to propel the machine; and

converting a second portion of the third DC power output to at least a portion of the second mechanical power output.

19. A machine, comprising:

a power source configured to generate a first mechanical power output;

a traction device configured to propel the machine;

a DC motor/generator operable to;

receive at least a portion of the first mechanical output and produce a DC power output; and

receive DC power and produce a second mechanical output;

a drivetrain operable to;

receive the DC power output and use the DC power output to drive the traction device; and

generate DC power when the traction device is operated in a dynamic braking mode; and

a braking grid operable to dissipate as heat a portion of the DC power generated by the drivetrain.

20. The machine of claim 19, further including:

an AC alternator operable to receive a portion of the first mechanical output and produce an AC power output;

a rectifier coupled with the AC alternator, the rectifier being operable to convert the AC power output to a DC power output combinable with the DC power output of the DC motor/generator.