Safety circuit and brush holder for preventing fault conditions in an alternator
First Claim
1. A fault protection circuit for an alternator, comprising:
- a first switch having a first terminal electrically connected to an intermediate supply node, a second terminal electrically connected to a rotor in the alternator, and a third terminal, wherein the first switch is configured to provide an excitation current to the rotor as a function of an excitation current control signal applied to the third terminal and a voltage at the intermediate supply node, so as to regulate an output voltage of the alternator;
an alternator controller circuit comprising an excitation current controller configured to generate the excitation current control signal;
a supervision circuit configured to detect a fault condition of the first switch and, responsive to this detection, generate a fault indication signal; and
a second switch electrically connected directly in series between the intermediate supply node and a supply voltage, the second switch configured to continuously disconnect the supply voltage from the intermediate supply node so long as the fault indication signal is active, and wherein the output voltage of the alternator provides the supply voltage.
1 Assignment
0 Petitions
Accused Products
Abstract
A fault protection circuit for an alternator is provided for preventing faults such as a prolonged full-field condition in the alternator. The fault protection circuit includes a safety switch that is opened when the alternator output voltage becomes too high, as may occur during a full-field condition caused by an electrical short, or when some other fault is detected within the alternator. The opening of this safety switch disconnects a supply voltage feeding an excitation current control switch. The excitation current control switch normally adjusts an excitation current provided to a rotor in the alternator, in order to regulate a voltage output from the alternator. By providing a safety switch that disconnects the supply voltage for the rotor excitation in the alternator, the alternator output voltage may be prevented from reaching excessive levels that may damage devices in an electrical system and a battery coupled to the alternator.
14 Citations
20 Claims
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1. A fault protection circuit for an alternator, comprising:
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a first switch having a first terminal electrically connected to an intermediate supply node, a second terminal electrically connected to a rotor in the alternator, and a third terminal, wherein the first switch is configured to provide an excitation current to the rotor as a function of an excitation current control signal applied to the third terminal and a voltage at the intermediate supply node, so as to regulate an output voltage of the alternator; an alternator controller circuit comprising an excitation current controller configured to generate the excitation current control signal; a supervision circuit configured to detect a fault condition of the first switch and, responsive to this detection, generate a fault indication signal; and a second switch electrically connected directly in series between the intermediate supply node and a supply voltage, the second switch configured to continuously disconnect the supply voltage from the intermediate supply node so long as the fault indication signal is active, and wherein the output voltage of the alternator provides the supply voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A brush holder for use in an alternator, the brush holder comprising:
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a housing retaining a brush configured to conduct an excitation current to a rotor in the alternator; a first switch retained by the housing, the first switch having a first terminal electrically connected to an intermediate supply node, a second terminal electrically connected to the brush, and a third terminal, wherein the first switch is configured to provide the excitation current to the rotor via the brush as a function of an excitation current control signal applied to the third terminal and a voltage at the intermediate supply node, so as to regulate an output voltage of the alternator; an alternator controller circuit retained by the housing, the alternator controller circuit comprising an excitation current controller configured to generate the excitation current control signal; a supervision circuit configured to detect a fault condition of the first switch and, responsive to this detection, generate a fault indication signal; and a second switch retained by the housing, the second switch electrically connected directly in series between the intermediate supply node and a supply voltage, the second switch configured to continuously disconnect the supply voltage from the intermediate supply node so long as the fault indication signal is active, and wherein the output voltage of the alternator provides the supply voltage. - View Dependent Claims (19)
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20. A method in an alternator for mitigating a fault condition of the alternator, the method comprising:
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providing an excitation current to a rotor of the alternator using a first switch having a first terminal electrically connected to an intermediate supply node, a second terminal electrically connected to the rotor, and a third terminal, wherein the excitation current provided to the rotor is a function of an excitation current control signal applied to the third terminal and a voltage at the intermediate supply node, so as to regulate an output voltage of the alternator, the excitation current control signal being generated by an alternator controller circuit that comprises an excitation current controller; detecting a fault condition of the first switch, via a supervision circuit, and generating a fault indication signal in response to said detecting and for as long as the fault condition persists; and responsive to the generated fault indication signal, continuously disconnecting a supply voltage from the intermediate supply node by opening a second switch electrically connected directly in series between the intermediate supply node and the supply voltage, and wherein the output voltage of the alternator provides the supply voltage.
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Specification