Field excitation for an alternator

• US 20050151515A1
• Filed: 01/14/2005
• Published: 07/14/2005
• Est. Priority Date: 01/14/2004
• Status: Active Grant

• Current Assignee: Vanner, Inc. (Vanner Holdings, Inc.)
• Original Assignee: Vanner, Inc. (Vanner Holdings, Inc.)
• Inventors: Cook, Alexander, Isurin, Alexander
• Granted Patent: US 7,106,030 B2
• Time in Patent Office: Days
• US Class Current: 322/28
• CPC Class Codes: H02M 3/1555 for the generation of a regulated current to a load whose impedance is substantially inductive
• CPC Class Codes: H02P 9/305 controlling voltage H02P9/302 takes precedence

Abstract

A system for controlling the excitation of an alternator field coil. The system comprises a capacitor forming a charge reservoir, a first and a second selectively operable switch connected to opposing ends of a field coil of the alternator, a first catch diode, and a second catch diode. At least one of the first and second switches are operated at a variable duty cycle and the capacitor both absorbs energy from the field coil and supplies energy to the field coil to regulate the magnetic field of the field coil, effective to regulate the output voltage of the alternator and rapidly compensate for changes in at least one load connected to the alternator.

Claims

1. In an alternator having a voltage source that includes an output and an electrical common, a field coil, a stator coil magnetically coupled to the field coil, a three-phase rectifier connected to the stator, and a variable load connected to the rectifier, a system for rapidly compensating for changes in power demand of the load comprising:

a capacitor connected between the output of the voltage source and the common, forming a charge reservoir;

a first selectively operable switch connected between the charge reservoir and a first end of the field coil;

a second selectively operable switch connected between the common and a second end of the field coil;

a first catch diode, having its anode connected to the common and its cathode connected to the first end of the field coil; and

a second catch diode, having its cathode connected to the charge reservoir and its anode connected to the second end of the field coil,

wherein at least one of the first and second switches is operated at a determinable variable duty cycle and the capacitor both absorbs energy from the field coil and supplies energy to the field coil to regulate the magnetic field of the field coil, effective to regulate the output voltage of the three-phase rectifier and rapidly compensate for changes in the power demand of at least one load connected to the three-phase rectifier.

2. The system of claim 1 wherein the charge reservoir is connected to the voltage source through a blocking diode arranged such that an anode of the blocking diode is connected to the voltage source and a cathode of the diode is connected to the capacitor.

3. The system of claim 1 wherein the duty cycle of the first switch is varied between about 0% and 100% and the second switch is kept substantially closed.

4. The system of claim 1 wherein the duty cycle of the first and second switches each varies between about 50% and 100% and the first switch is actuated synchronously with the second switch.

5. The system of claim 1 wherein the duty cycle of the first and second switches each varies between about 0% and 100% and the first switch is actuated synchronously with the second switch.

6. The system of claim 1, further comprising a controller to monitor the load and control the actuation of the first and second switches to adjust the output of the alternator to compensate for changes in the load.

7. The system of claim 6 wherein the output of the alternator is increased when the load is increased, and decreased when the load is decreased.

8. The system of claim 6, further comprising a field coil voltage feedback signal.

9. The system of claim 8, further comprising a field coil current feedback signal.

10. The system of claim 9 wherein the controller is responsive to the voltage and current feedback signals and adjusts the current in the field coil to a level corresponding to the levels of the voltage and current feedback signals.

11. The system of claim 10, further comprising a divider circuit that provides an output signal corresponding to the impedance of the field coil.

12. The system of claim 11 wherein the controller reduces the duty cycle of the first and second switches when the impedance of the field coil exceeds a threshold value.

13. In an alternator having a voltage source that includes an output and an electrical common, a field coil, a stator coil magnetically coupled to the field coil, a three-phase rectifier connected to the stator, and a variable load connected to the rectifier, a system for rapidly compensating for changes in power demand of the load comprising:

a capacitor connected between the output of the voltage source and the common, forming a charge reservoir;

a first selectively operable switch connected between the charge reservoir and a first end of the field coil;

a second selectively operable switch connected between the common and a second end of the field coil;

a first catch diode, having its anode connected to the common and its cathode connected to the first end of the field coil;

a second catch diode, having its cathode connected to the charge reservoir and its anode connected to the second end of the field coil, and

a controller to monitor the load and control the actuation of the first and second switches,

wherein at least one of the first and second switches are operated by the controller at a determinable variable duty cycle and the capacitor both absorbs energy from the field coil and supplies energy to the field coil to regulate the magnetic field of the field coil, effective to regulate the output voltage of the three-phase rectifier and rapidly compensate for changes in power demand of at least one load connected to the three-phase rectifier, such that the output of the alternator is increased when the load is increased, and decreased when the load is decreased.

14. The system of claim 13 wherein the charge reservoir is connected to the voltage source through a blocking diode arranged such that an anode of the blocking diode is connected to the voltage source and a cathode of the diode is connected to the capacitor.

15. The system of claim 13, further comprising a field coil voltage feedback signal.

16. The system of claim 15, further comprising a field coil current feedback signal.

17. The system of claim 16 wherein the controller is responsive to the voltage and current feedback signals and adjusts the current in the field coil to a level corresponding to the levels of the voltage and current feedback signals.

18. The system of claim 17, further comprising a divider circuit that provides an output signal corresponding to the impedance of the field coil.

19. The system of claim 18 wherein the controller reduces the duty cycle of the first and second switches when the impedance of the field coil exceeds a threshold value.

20. A method for controlling the excitation of an alternator having a voltage source that includes an output and an electrical common, a field coil, a stator coil magnetically coupled to the field coil, a three-phase rectifier connected to the stator, and a variable load connected to the rectifier comprising the steps of:

forming a charge reservoir by connecting a capacitor between the output of the voltage source and the common;

selectively operating a first switch connected between the charge reservoir and a first end of the field coil;

selectively operating a second switch connected between the common and a second end of the field coil;

connecting an anode of a first catch diode to the common, and connecting a cathode of the first catch diode to the first end of the field coil,

connecting a cathode of a second catch diode to the charge reservoir, and connecting an anode of the second catch diode to the second end of the field coil; and

operating at least one of the first and second switches at a determinable variable duty cycle such that the capacitor both absorbs energy from the field coil and supplies energy to the field coil to regulate the magnetic field of the field coil, effective to regulate the output voltage of the three-phase rectifier and rapidly compensate for changes in at least one load connected to the three-phase rectifier.

21. The method of claim 20, further comprising the step of connecting the charge reservoir to the voltage source through a blocking diode arranged such that an anode of the blocking diode is connected to the voltage source and a cathode of the diode is connected to the capacitor.

22. The method of claim 20, further comprising the steps of varying the duty cycle of the first switch between about 0% and 100% and keeping the second switch substantially closed.

23. The method of claim 20, further comprising the steps of varying the duty cycle of each of the first and second switches between about 50% and 100% and synchronously actuating the first and second switches.

24. The method of claim 20, further comprising the steps of varying the duty cycle of each of the first and second switches between about 0% and 100% and synchronously actuating the first and second switches.

25. The method of claim 20, further comprising the step of adding a controller to monitor the load and control the actuation of the first and second switches to adjust the output of the alternator to compensate for changes in the load.

26. The method of claim 25, further comprising the step of increasing the output of the alternator when the load is increased, and decreasing the output of the alternator when the load is decreased.

27. The method of claim 25, further comprising the step of monitoring the voltage of the field coil.

28. The system of claim 27, further comprising the step of monitoring the current of the field coil.

29. The method of claim 28, further comprising the steps of monitoring the voltage and current of the field coil and adjusting the current in the field coil to a level corresponding to the voltage and current feedback signals.

30. The method of claim 29, further comprising the step of producing an output signal corresponding to the impedance of the field coil.

31. The method of claim 30, further comprising the step of reducing the duty cycle of the first and second switches when the impedance of the field coil exceeds a threshold value.