AU2015201770B2

AU2015201770B2 - Self exciting alternator circuit

Info

Publication number: AU2015201770B2
Application number: AU2015201770A
Authority: AU
Inventors: Giuliano Res
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-04-08
Filing date: 2015-04-08
Publication date: 2021-03-25
Anticipated expiration: 2035-04-08
Also published as: ZA201502327B; AU2015201770A1

Abstract

An alternator having a voltage boosting circuit driven by at least two stator winding conductors. The output of the voltage boosting circuit is connected to a signal conditioning circuit which adjusts the voltage boosting signal to deliver a suitable signal to turn on a current controller. The current controller controls the current through a field coil which produces a magnetic field. The magnetic field induces a corresponding electric current in the stator windings due to the spinning of the rotor. The alternator further comprises a rectifier circuit for rectifying and smoothing the stator windings output. 1 . ... . . ... ... -- --- -- .. .... -- -- -- --- ---- - -- -------- ........... . ------ -- ---- --- .......... Figur 2

Description

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Figur 2

SELF EXCITING ALTERNATOR CIRCUIT BACKGROUND OF THE INVENTION

[0001] The present invention relates to alternators and more particularly relates to improvements in the operation of alternator circuitry and more particularly to a circuit that can provide adequate power to field current control circuitry without the need for a permanent magnet. The invention further relates to an alternator circuit which is capable of boosting the small voltages that are generated by the stator windings as the rotor spins resulting from the small residual magnetic fields that naturally occur in an alternator's components moving across the stator windings. Furthermore the invention relates to an alternator having a circuit which allows the alternator to maintain output voltage regulation without any load.

PRIOR ART

[0002] Alternators are used in numerous machines to convert mechanical power into electrical power. Alternators are widely used in industry and mining environments in conjunction with other machinery and in use, converts the mechanical power from a rotating shaft into electrical power and heat. The electric power generated is typically used to drive electrical equipment. The typical modern alternator has a permanent magnet and a field coil, both fixed to the alternator chassis, to provide a magnetic field to a spinning rotor. The rotor is designed to split the magnetic field up into a number of interlaced magnetic fields which, as the rotor spins, are directed to pass across stator windings. The stator windings are also mounted in some way onto the alternator chassis. The moving magnetic fields induce electrical currents in the stator windings.

[0003] Generally, alternators are designed so the stator windings produce three voltage sine waves that are 1200 phase shifted from each other. The stator output conductors are connected to a positive and a negative output conductor, typically using power diodes, to provide a rectified DC power output. There is generally a significant voltage ripple on the rectified DC voltage. The output of the alternator is controlled by varying the amount of current in the field coil to vary the strength of the magnetic field.

[0004] A number of alternator designs use sophisticated electronic field current control circuitry. In these situations the control circuitry typically requires power prior to delivering current to the field coil. To provide the start-up field coil current and control circuitry power either an external power supply, such as a battery, is required or a magnetic field must be present without any coil current. When using a start-up magnetic field, circuitry is required that is capable of powering the control circuit from the small stator windings power produced due to the start-up magnetic field. A permanent magnet is typically used to provide the start-up magnetic field.

[0005] An alternator's rectified output voltage depends on a number of factors. Two notable factors are the strength of the magnetic field and the size of the load being powered by the alternator. The range of alternator power output for a given rotational speed is dependent on the range of the magnetic field controlled by the field coil. A field coil is typically driven to add to the permanent magnet's magnetic field. In this case the minimum magnetic field is the permanent magnet's magnetic field and this in turn defines the minimum load that must be loading the alternator's output to keep the output voltage within specification. In some machines the minimum load requirement is undesirable. In many machines it is also often desirable to be able to completely turn off the external load without losing the output voltage regulation.

[0006] These factors lead to design trade-offs between the alternator's minimum load and the cost and complexity of the alternator's design. Stronger permanent magnets deliver more start-up power leading to simpler circuitry driving the field coil. Stronger permanent magnets also lead to higher minimum loads required to avoid over-voltage problems at higher rotational speeds. Minimum loads are typically a couple of amps.

[0007] Alternators heretofore devised and utilized are known to consist basically of familiar, expected and obvious structural configurations, notwithstanding the plurality of designs encompassed by the prior art which have been developed for the fulfilment of the objectives and requirements of alternator power generation. While the prior art alternators fulfil their functions, particular objectives and requirements, the aforementioned prior art does

not disclose an alternator which includes a circuit that can provide adequate power to

field current control circuitry without the need for a permanent magnet.

SUMMARY OF THE INVENTION

[0008] The present invention provides an alternator circuit that can provide adequate power to field current control circuitry without the need for a permanent magnet. The invention further provides an alternator circuit which is capable of boosting the small voltages that are generated by the stator windings as the rotor spins resulting from the small residual magnetic fields that naturally occur in an alternator's components moving across the stator windings. The invention also provides to an alternator having a circuit which allows the alternator to maintain output voltage regulation without any load.

[0009] According to a preferred embodiment the circuit boosts the small voltages that are generated by the alternator stator windings as the rotor spins resulting from the small residual magnetic fields that naturally occur in an alternator's components moving across the stator windings.

[0010] These residual magnetic fields are too small to provide the necessary power using existing alternator circuitry. A smaller start-up magnetic field also leads to alternator designs based on the present invention to have lower minimum load requirements.

[0011] In its broadest form the present invention comprises:

an alternator circuit which provides power to field current control circuitry without the need for a permanent magnet, the circuit operable to boost small voltages that are generated by the alternator stator windings as the rotor spins.

[0012] In another broad form the present invention comprises:

an alternator having a voltage boosting circuit which provides power to field current control circuitry without the need for a permanent magnet; the voltage boosting circuit having at least one power phase providing power to a field coil of the alternator; the at least one power phase in communication with windings of the alternator stator and connected to a charge capacitor; the circuit driven by at least two stator winding conductors, an output of the voltage boosting circuit being connected to a signal conditioning circuit which adjusts the voltage boosting circuit signal to deliver a suitable signal to turn on a current controller.

[0013] In another broad form the present invention comprises;

An alternator voltage boosting circuit in communication with an alternator and which

provides power to field current control circuitry without the need for a permanent magnet, the voltage boosting circuit having at least one power phase; the at least one power phase in communication with windings of the alternator stator and connected to charge a capacitor, the at least one power phase providing power to a field coil of the alternator; the circuit driven by at least two stator winding conductors; an output of the voltage boosting circuit being connected to a signal conditioning circuit which adjusts the voltage boosting signal to deliver a suitable signal to turn on a current controller.

[0014] The present invention provides an alternative to the known prior art and the shortcomings identified. The foregoing and other objects and advantages will appear from the description to follow. In the description reference is made to the accompanying representations, which forms a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. In the accompanying illustrations, like reference characters designate the same or similar parts throughout the several views. The following detailed description is, therefore, not to be taken in a limiting sense and the scope of the present invention is best defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will now be described in broad detail according to preferred but non limiting embodiments wherein;

Figure 1 shows s a cross sectional view of key components of a typical alternator.

Figure 2 shows a circuit diagram according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION

[0016] Although the invention will be described according to preferred embodiments it will be appreciated that other variants are contemplated. The design and construction may be variously modified, without departing from the spirit and scope of the invention, as defined herein.

[0017] Figure 1 shows a cross section illustrating the main features of a typical alternator 1. Alternator 1 comprises input shaft 10 with associated rotor 12 affixed thereto. Rotor 12 is designed to appropriately split the magnetic field from the field coil

14 and deliver the maximum amount of magnetic flux to pass across the stator windings 16 as the rotor 12 spins. The gap between the rotor 12 and stator windings 16 is kept as small as possible to maximize the magnetic flux. Likewise the air gaps between the spinning input shaft 10 and rotor components and the stationary field coil mounting components 18 is kept as small as possible so as to minimize the magnetic impedance to the magnetic field.

[0018] Figure 2 shows a circuit layout diagram according to a preferred embodiment of the present invention. The three power phases 20a 20b and 20c from the stator windings 16, shown in figure 1, are connected to three diodes 22a, 22b and 22c to charge a capacitor 24 and provide power to the field coil 14. The three power phases 20a 20b and 20c are also connected to the primary winding of a transformer 26. Transformer 26 boosts an input voltage signal which is then rectified by diode 28 and, during the bootstrap process, current passes through the signal conditioning circuitry 30 and turns on the electronic switch 32. Once the electronic switch 32 is on, a small current produced by the stator windings due to the residual magnetic fields starts to flow through the diodes 22 and through the field coil 14. The capacitor 24 helps to stabilize the rectified voltage provided to the field coil. Once current begins to flow through the field coil 14 the voltage output by the three power phases 20a 20b and 20c increases which in turn increases the power to the field coil and this bootstrapping cycle continues to build the output voltage until it is sufficient to operate the alternator's control system. The control system then provides a signal to the signal conditioning circuitry 30 to take over control of the electronic switch and begin controlling the output of the alternator.

[0019] Using the circuit according to the present invention, an alternator can be designed to maintain output voltage regulation without any load. There are a number of alternative embodiments of the present invention. For example, the transformer 26 may operate using only one power phase. The electronic switch 32 could be any one of a number of power switches that are known by persons skilled in the art. It is possible to have only one or two diodes 22 providing power from only one or two power of the phases 20a, 20b, and 20c. The transformer 26 could be replaced with other voltage boosting circuits that are common in the art which may or may not require diode 28. A second electronic switch could be used for normal operation and the electronic switch 32 only used for the bootstrap process.

[0020] The general purpose of the present invention, which is described herein in detail, is to provide a useful alternative to the know art and which has additional advantages along with novel features that result in a new, advantageous alternator which is not anticipated, rendered obvious, suggested, or even implied by any of the prior art devices, either alone or in any combination thereof.

[0021] It will be recognized by persons skilled in the art that numerous variations and modifications may be made to the invention as broadly described herein without departing from the overall spirit and scope of the invention.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. An alternator voltage boosting circuit in communication with an alternator and which provides power to field current control circuitry without the need for a permanent magnet, the voltage boosting circuit having at least one power phase; the at least one power phase in communication with windings of the alternator stator and connected to charge a capacitor, the at least one power phase providing power to a field coil of the alternator; the circuit driven by at least two stator winding conductors; an output of the voltage boosting circuit being connected to a signal conditioning circuit which adjusts the voltage boosting signal to deliver a suitable signal to turn on a current controller.

2. A circuit according to claim 1 wherein each said at least one power phase is connected to at least one diode.

3. A circuit according to claim 2 wherein there are three power phases.

4. A circuit according to claim 1 wherein there are three power phases with each power phase respectively connected to one of three diodes.

5. A circuit according to claim 4 wherein said power phases are also connected to a primary winding of a transformer.

6. A circuit according to claim 5 wherein said transformer boosts an input voltage signal which is then rectified by a diode.

7. A circuit according to claim 6 wherein, current passes through signal conditioning circuitry and turns on an electronic switch.

8. A circuit according to claim 7 wherein current passes through said signal conditioning circuitry during a bootstrap process.

9. A circuit according to claim 8 wherein upon actuation of said electronic switch, a small current produced by the windings of the stator starts to flow through the diodes and through the field coil .

10. A circuit according to claim 9 wherein current produced by the windings of the stator is due to residual magnetic fields.

11. A circuit according to claim 10 wherein the capacitor contributes to stabilisation of the voltage rectified by said diode and provided to the field coil.

12. A circuit according to claim 11 wherein when current begins to flow through the field coil ,voltage output by said three power phases increases.

13. A circuit according to claim 12, wherein when said voltage output by said three power phases increases, the power to the field coil is increased.

14. A circuit according to claim 13 wherein the bootstrap process continues to build the output voltage until it is sufficient to operate a control system of the alternator.

15. A circuit according to claim 14 wherein the control system provides a signal to said signal conditioning circuitry to assume control of the electronic switch thereby controlling output of the alternator.

16. A circuit according to claim 15 wherein the alternator is capable of maintaining output voltage regulation without any load.

17. A circuit according to claim 16 wherein the transformer is capable of operation using one of said three power phases.

18. A circuit according to claim 17 wherein one diode is operated using only one power phase.

19. A circuit according to claim 18 wherein the electronic switch is only used for the bootstrap process.

20. A circuit according to claim 19 further comprising a second electronic switch.

21. A circuit according to claim 1, wherein the voltage boosting circuit boosts an input voltage signal.

22. A circuit according to claim 21 further comprising at least one diode.

23. A circuit according to claim 22 wherein, the at least one diode rectifies the input voltage signal.

24. An alternator having a voltage boosting circuit which provides power to field current control circuitry without the need for a permanent magnet; the voltage boosting circuit having at least one power phase providing power to a field coil of the alternator; the at least one power phase in communication with windings of the alternator stator and connected to a charge capacitor ; the circuit driven by at least two stator winding conductors, an output of the voltage boosting circuit being connected to a signal conditioning circuit which adjusts the voltage boosting circuit signal to deliver a suitable signal to turn on a current controller.

25. An alternator according to claim 24 wherein, the current controller controls the current through the field coil.

26. An alternator according to claim 25 wherein, current through the field coil produces a magnetic field.

27. An alternator according to claim 26 wherein, the magnetic field induces a corresponding electric current in the stator windings due to the spinning of the rotor.

28. An alternator according to claim 27 further comprising, a rectifier circuit for rectifying and smoothing the stator windings output.

29. An alternator according to claim 28 wherein the rectifier circuit delivers current to the field coil.

30. An alternator according to claim 29 wherein the alternator relies on residual magnetic fields of the alternator components, thereby not requiring the permanent magnet to provide a stronger magnetic field to generate start-up power.