EP0256689A2
Expired / Lapsed
EP
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High DC voltage power supply for motor vehicle electrical circuit
Assignee: Motors Liquidation Co
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Filing: 1987-07-24
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Granted: —
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Expires: 2007-07-24
Abstract
Abstract A high DC voltage power supply includes a three-phase autotransformer (42) and a three-phase full-wave rectifier (44) applied to the usual motor vehicle electrical circuit (10) of the low DC voltage type. The low three-phase AC voltage of the usual circuit is transformed by the autotransformer to obtain a high three-phase AC voltage which is then rectified by the rectifier to provide a high DC voltage. The load (40) energized by the high DC voltage is ungrounded to reduce the voltage available for inadvertent discharge from either load terminal (62,66) to ground (16). Switching apparatus (46,48,80) is provided for selectively applying the low three-phase AC voltage to the autotransformer only when it is desired to energize the load thereby avoiding at all other times the energy losses that would otherwise be associated with energization of the autotransformer. In one embodiment, the load is a windshield heater element and the autotransformer has multiple sets of input taps (54,56) to provide deice and defog modes of operation, respectively. The tapping of the autotransformer on the input or primary side yields efficiencies in the construction and operation of the autotransformer. In another embodiment, a current transformer is provided for measuring the AC current through one of the input or output leads of the autotransformer as an indication of the DC current through the load thereby to detect an abnormally low load current condition. The engine driven generator (22) of the motor vehicle electrical circuit is excited from a voltage source (38) independent of the low three-phase AC voltage put out by the generator, at least during any period that the generator is overloaded, thereby to prevent a degenerative collapse in the generator output voltage.
Inventors
- 👤 Robert W. Campbell
- 👤 Donald O. Ruff
- 👤 David W. Caldwell
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 09:25
CPC Classifications
H; H02; H02J; H02J7/00; H02J7/14; H02J7/1438
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
258 words
A motor vehicle electrical circuit (10) of the type providing a low DC voltage with respect to ground (16) and including a storage battery (12) for providing standby power at the low DC voltage, a generator (22) for producing a low three-phase AC voltage, and a three-phase rectifier (32) for converting the low three-phase AC voltage to the low DC voltage for charging the storage battery and supplying various low DC voltage loads (20), characterised by a three-phase autotransformer (42) of the voltage step-up type for transforming the low three-phase AC voltage put out by the generator to provide a high three-phase AC voltage where the three-phase autotransformer is unrelated to the production of the low DC voltage; a three-phase full-wave rectifier (44) for rectifying the high three-phase AC voltage put out by the three-phase autotransformer to provide a high DC voltage; and a high DC voltage load (40) having a pair of ungrounded terminals (62,66) across which the high DC voltage is applied such that with respect to ground the voltage at one terminal of the high DC voltage load is above ground and the voltage at the other terminal of the high DC voltage load is below ground thereby to reduce the voltage available for inadvertent discharge from either terminal of the high DC voltage load to ground by up to approximately one-half the voltage that would otherwise be available for inadvertent discharge from the ungrounded terminal of the high DC voltage load to ground if one terminal of the high DC voltage load was grounded.
Claim 2
Dependent Claim
258 words
A motor vehicle electrical circuit (10) of the type providing a low DC voltage with respect to ground (16) and including a storage battery (12) for providing standby power at the low DC voltage, a generator (22) for producing a low three-phase AC voltage, and a three-phase rectifier (32) for converting the low three-phase AC voltage to the low DC voltage for charging the storage battery and supplying various low DC voltage loads (20), characterised by a three-phase autotransformer (42) of the voltage step-up type for transforming the low three-phase AC voltage put out by the generator to provide a high three-phase AC voltage where the three-phase autotransformer is unrelated to the production of the low DC voltage; a three-phase full-wave rectifier (44) for rectifying the high three-phase AC voltage put out by the three-phase autotransformer to provide a high DC voltage; and a high DC voltage load (40) having a pair of ungrounded terminals (62,66) across which the high DC voltage is applied such that with respect to ground the voltage at one terminal of the high DC voltage load is above ground and the voltage at the other terminal of the high DC voltage load is below ground thereby to reduce the voltage available for inadvertent discharge from either terminal of the high DC voltage load to ground by up to approximately one-half the voltage that would otherwise be available for inadvertent discharge from the ungrounded terminal of the high DC voltage load to ground if one terminal of the high DC voltage load was grounded.
Claim 3
Dependent Claim
59 words
A motor vehicle electrical circuit as claimed in Claim 1 characterised by applying means (46,48,80) for selectively applying the low three-phase AC voltage to the three-phase autotransformer (42) only when it is desired to energize the high DC voltage load (40) so as to avoid at all other times the energy losses associated with energization of the three-phase autotransformer.
Claim 4
Dependent Claim
186 words
A motor vehicle electrical circuit as claimed in Claim 1, characterised in that the three-phase autotransformer (42) has first and second sets of taps (54,56) to provide different voltage step-up transformation ratios in response to application of the low three-phase AC voltage to produce corresponding first and second high three-phase AC voltages where the amplitude of the first high three-phase AC voltage is greater than the amplitude of the second high three-phase AC voltage; and in that the three-phase full-wave rectifier (44) rectifies the first and second high three-phase AC voltages to produce corresponding first and second high DC voltages across the high DC voltage load (40) where the magnitude of the first high DC voltage is greater than the magnitude of the second high DC voltage to provide high and low power modes of operation; the first and second sets of taps being input or primary taps as opposed to output or secondary taps thereby enabling the three-phase autotransformer to be constructed with less core material and/or winding turns and to be operated more efficiently than would otherwise be possible with output or secondary taps.
Claim 5
Dependent Claim
108 words
A motor vehicle electrical circuit as claimed in Claim 3, characterised in that the high DC voltage load (40) is a high power window glass heater element; and by applying means (46,48,80) for selectively applying the low three-phase AC voltage to the first set of input taps (54) of the three-phase autotransformer (42) to energize the window glass heater element with the first high DC voltage to provide a high heat mode of operation or to the second set of input taps (56) of the three-phase autotransformer to energize the window glass heater element with the second high DC voltage to provide a low heat mode of operation.
Claim 6
Dependent Claim
197 words
A motor vehicle electrical circuit as claimed in any one of the preceding claims wherein the generator (22) produces a low three-phase AC voltage at a power output determined by the driven speed of the generator and the amount of excitation of the generator, and wherein the high DC voltage load (40) is capable of overloading the generator by imposing a power requirement upon the generator that when combined with the power requirement imposed upon the generator by the low DC voltage loads (20) is greater than the maximum power that the generator can deliver at the driven generator speed such that a degenerative collapse in the low three-phase AC voltage put out by the generator would result if the generator was excited with a voltage derived in dependence upon the low three-phase AC voltage; the circuit being characterised by exciting means (38) for exciting the generator with a voltage derived from the storage battery (12) or some other voltage source not dependent upon the low three-phase AC voltage put out by the generator during at least the time that the generator is overloaded so as to prevent a degenerative collapse in the low three-phase AC voltage.
Claim 7
Dependent Claim
19 words
A motor vehicle electrical circuit as claimed in Claim 5 wherein the exciting means is a voltage regulator (38).
Claim 8
Dependent Claim
61 words
A motor vehicle electrical circuit as claimed in any one of the preceding claims, characterised by measuring means (118,92,126) for measuring the magnitude of the AC current flow through the three-phase autotransformer (42) as an indication of the magnitude of the DC current flow through the high DC voltage load (40) to detect the presence of an abnormal current condition therein.
Claim 9
Dependent Claim
74 words
A motor vehicle electrical circuit as claimed in any one of Claims 3 to 7, characterised by controlling means (92,110,126) for controlling the vehicle engine (28) to drive the generator (22) during the high heat mode of operation at a frequency greater than the frequency corresponding to the normal idle speed of the vehicle engine so as to meet the increased power requirement imposed upon the generator during the high heat mode of operation.
Claim 10
Dependent Claim
100 words
A motor vehicle electrical circuit as claimed in any one of the preceding claims for a motor vehicle having a transmission (96) operable between park, neutral and one or more drive states, the circuit being characterised by means (92,98,126) effective when the transmission is in the park or neutral state to raise the idle speed of the vehicle engine (28) from the normal idle speed to an elevated idle speed at which the generator (22) is driven at a frequency high enough to produce sufficient power to satisfy the combined power requirement of the high and low DC voltage loads.
Claim 11
Dependent Claim
27 words
A motor vehicle electrical circuit as claimed in any one of claims 5 to 9, in which the high DC voltage load is a high power load.
References Cited (Backward Citations)
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