US3881137A
Expired / Lapsed
US
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Frequency selective damping circuits
Assignee: Associated Electrical Industries Ltd
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Filing: 1974-01-16
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Granted: 1975-04-29
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Expires: 1994-01-16
Abstract
Abstract In A.C. power systems, large capacitors used in conjunction with synchronous or induction machines, or with saturable reactors, are prone to self-excited oscillation at harmonic or sub-harmonic frequencies. Damping circuits are known in which supply-frequency capacitor current is kept away from a damping resistance path by a series or shunt resonant circuit. The invention provides improved damping of harmonic or sub-harmonic oscillations by adding capacitance or inductance, or both, to achieve a resonance at the parasitic frequency and so force the parasitic current through the damping resistance.
Inventors
- 👤 Hemesh Laxmidas Thanawala
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 17:02
CPC Classifications
H; H02; H02H; H02H9/00; H02H9/005; H02H9/007; H03; H03H; H03H7/00; H03H7/01; H03H7/17; H03H7/1741; H03H7/1791
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
131 words
A frequency selective damping circuit for the suppression of parasitic resonances associated with a voltage compensating supply-frequency capacitor, said damping circuit comprising two parallel paths one of which is a damped path including resistance and one of which is an undamped path, and a resonant circuit tuned to said supply frequency and connected to bias current of the supply frequency toward said undamped path, said supplyfrequency capacitor being connected in series with said undamped path, said damping circuit further comprising reactive circuit means which, in combination with said resonant circuit provides a further resonant circuit, at the resonant frequency of which, current is biased toward said damped path, the arrangement being such that current of the supply frequency is relatively undamped and current of a predetermined other frequency is selectively damped.
Claim 2
Dependent Claim
131 words
A frequency selective damping circuit for the suppression of parasitic resonances associated with a voltage compensating supply-frequency capacitor, said damping circuit comprising two parallel paths one of which is a damped path including resistance and one of which is an undamped path, and a resonant circuit tuned to said supply frequency and connected to bias current of the supply frequency toward said undamped path, said supplyfrequency capacitor being connected in series with said undamped path, said damping circuit further comprising reactive circuit means which, in combination with said resonant circuit provides a further resonant circuit, at the resonant frequency of which, current is biased toward said damped path, the arrangement being such that current of the supply frequency is relatively undamped and current of a predetermined other frequency is selectively damped.
Claim 3
Dependent Claim
37 words
A damping circuit according to claim 2 wherein the first resonant circuit is a shunt circuit, said damping path comprising said shunt circuit in series with said resistance and the other, undamped, parallel path comprising said capacitor.
Claim 4
Dependent Claim
34 words
A damping circuit according to claim 2 wherein said reactive circuit means comprises an inductor connected in series with said resistance to provide a damping resonance at a frequency higher than the supply frequency.
Claim 5
Dependent Claim
35 words
A damping circuit according to claim 2 wherein said reactive circuit means and said resistance are together constituted by an inductive resistor to provide a damping resonance at a frequency higher than said supply frequency.
Claim 6
Dependent Claim
33 words
A damping circuit according to claim 2 wherein said reactive means comprises an inductor connected in parallel with said resistance to provide a damping resonance at a frequency higher than said supply frequency.
Claim 7
Dependent Claim
34 words
A damping circuit according to claim 2 wherein said reactive circuit means comprises a capacitor connected in series with said resistance to provide a damping resonance at a frequency lower than said supply frequency.
Claim 8
Dependent Claim
34 words
A damping circuit according to claim 2 wherein said reactive circuit means comprises a capacitor connected in parallel with said resistance to provide a damping resonance at a frequency lower than said supply frequency.
Claim 9
Dependent Claim
44 words
A damping circuit according to claim 1 wherein the first resonant circuit is a series resonant circuit, said damped parallel path comprising said resistance and the other, undamped, parallel path comprising said series resonant circuit, said capacitor being connected in series with each path.
Claim 10
Dependent Claim
34 words
A damping circuit according to claim 8 wherein said reactive circuit means comprises a capacitor connected in parallel with said resistance to provide a damping resonance at a frequency higher than said supply frequency.
Claim 11
Dependent Claim
34 words
A damping circuit according to claim 8 wherein said reactive circuit means comprises a capacitor connected in series with said resistance to provide a damping resonance at a frequency higher than said supply frequency.
Claim 12
Dependent Claim
34 words
A damping circuit according to claim 8 wherein said reactive circuit means comprises an inductor connected in parallel with said resistance to provide a damping resonance at a frequency lower than said supply frequency.
Claim 13
Dependent Claim
34 words
A damping circuit according to claim 8 wherein said reactive circuit means comprises an inductor connected in series with saiD resistance to provide a damping resonance at a frequency lower than said supply frequency.
Claim 14
Dependent Claim
37 words
In a voltage compensating circuit for an A.C. power system including a damping circuit according to claim 1, said supply frequency capacitor is connected in series with a saturable core reactor to the A.C. power supply line.
Claim 15
Dependent Claim
57 words
In a voltage compensating circuit according to claim 13, said saturable core reactor is tapped at a point such that the part of the reactor between the tapping point and said capacitor, and the capacitor itself, together provide a series resonant circuit resonant at the supply frequency and constituting the first resonant circuit of said damping circuit.
Claim 16
Dependent Claim
145 words
A frequency selective damping circuit for the suppression of parasitic resonances associated with a voltage compensating supply-frequency capacitor, said damping circuit comprising two parallel paths one of which is a damped path including resistance and one of which is an undamped path, and a resonant circuit turned to said supply frequency and connected to bias current of the supply frequency toward said undamped path, said supply-frequency capacitor being connected in series with said undamped path, said damping circuit further comprising reactive circuit means, including reactances of opposite kinds, which, in combination with said resonant circuit provides two further resonant circuits, having resonant frequencies above and below said supply frequency respectively at which said resonant frequencies, current is biased toward said damped path, the arrangement being such that current of the supply frequency is relatively undamped and current of two predetermined other frequencies is selectively damped.
Claim 17
Dependent Claim
145 words
A frequency selective damping circuit for the suppression of parasitic resonances associated with a voltage compensating supply-frequency capacitor, said damping circuit comprising two parallel paths one of which is a damped path including resistance and one of which is an undamped path, and a resonant circuit turned to said supply frequency and connected to bias current of the supply frequency toward said undamped path, said supply-frequency capacitor being connected in series with said undamped path, said damping circuit further comprising reactive circuit means, including reactances of opposite kinds, which, in combination with said resonant circuit provides two further resonant circuits, having resonant frequencies above and below said supply frequency respectively at which said resonant frequencies, current is biased toward said damped path, the arrangement being such that current of the supply frequency is relatively undamped and current of two predetermined other frequencies is selectively damped.
Claim 18
Dependent Claim
37 words
A damping circuit according to claim 15 wherein the first resonant circuit is a shunt circuit, said damping path comprising said shunt circuit in series with said resistance and the other, undamped, parallel path comprising said capacitor.
Claim 19
Dependent Claim
40 words
A damping circuit according to claim 11 wherein said reactive circuit means comprises an inductor and capacitor connected in series with each other and with said resistance to provide damping resonances at frequencies higher and lower than said supply frequency.
Claim 20
Dependent Claim
42 words
A damping circuit according to claim 16 wherein said reactive circuit means comprises an inductor and capacitor connected in series with each other and in parallel with said resistance to provide damping resonances at frequencies higher and lower than said supply frequency.
Claim 21
Dependent Claim
44 words
A damping circuit according to claim 15 wherein the first resonant circuit is a series resonant circuit, said damped parallel path comprising said resistance, and the other, undamped, parallel path comprising said series resonant circuit, said capacitor being connected in series with each path.
Claim 22
Dependent Claim
41 words
A damping circuit according to claim 19 wherein said reactive circuit means comprises an inductor and a capacitor connected in parallel with each other and with said resistance to provide damping resonances at frequencies lower and higher than said supply frequency.
Claim 23
Dependent Claim
43 words
A damping circuit according to claim 19 wherein said reactive circuit means comprises an inductor and a capacitor connected in parallel with each other and in series with said resistance to provide damping resonances at frequencies lower and higher than said supply frequency.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-28 | 1978-10-28 | 1979-04-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-28 | 1982-10-28 | 1983-04-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-28 | 1986-10-28 | 1987-04-29 | $7700.00 | Window Closed / Lapsed |