US4066954A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Frequency converter
Assignee: Siemens AG
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Filing: 1976-09-15
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Granted: 1978-01-03
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Expires: 1996-09-15
Abstract
Abstract A parallel resonant circuit frequency converter, in which, through the resonant circuit voltage picked up by a voltage sensor and the inverter output current picked up by a current sensor, a firing instant for the inverter thyristors is determined prior to every zero crossing of the resonant circuit voltage by means of an evaluating circuit, taking into consideration the commutation and the protection time. To detect commutation short circuits, the currents of bridge arms with a common d-c terminal are measured by the current sensor and added up to an a-c current. The current sensor and the voltage sensor are followed by a monitoring device which releases a pulse if between one of the firing instants and the corresponding zero crossing of the resonant circuit voltage the inverter output current and the resonant circuit voltage remain in phase or are in phase opposition after the zero crossing.
Inventors
- 👤 Lovro Vukasovic
- 👤 Janos Raduka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 11:32
CPC Classifications
H; H02; H02M; H02M7/00; H02M7/42; H02M7/44; H02M7/48; H02M7/505; H02M7/515; H02M7/523; H02M7/525
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
249 words
In a frequency converter comprising an inverter with thyristors in a bridge circuit, the a-c outputs of which are connected to a resonant circuit and the d-c inputs of which are connected to an a-c voltage source, via an intermediate d-c link with a smoothing choke and a controlled rectifier and having a voltage sensor for determining the resonant circuit voltage and a current sensor for determining the inverter output current, the outputs of which are inputs to evaluating circuit, the output of which is connected to the control unit for the thyristors of the inverter, which evaluating circuit determines by means of a trigger pulse, prior to every zero crossing of the resonant circuit voltage, a firing instant for thyristors of diagonal bridge arms of the inverter, the position of which depends on the commutation time of the inverter and the protection time of the thyristors, the improvement comprising: a. the current sensor being one which measures and adds up to an ac current the currents in bridge arms with a common d-c terminal; and b. a monitoring circuit having as inputs the outputs of the current and the voltage sensor and developing at its output a pulse if, between a firing instant (t z ) and the corresponding zero crossing (t o ) of the resonant circuit voltage, the inverter output current and the resonant circuit voltage remain in phase or developing said pulse if said current and voltage are in phase opposition after the zero crossing.
Claim 2
Dependent Claim
249 words
In a frequency converter comprising an inverter with thyristors in a bridge circuit, the a-c outputs of which are connected to a resonant circuit and the d-c inputs of which are connected to an a-c voltage source, via an intermediate d-c link with a smoothing choke and a controlled rectifier and having a voltage sensor for determining the resonant circuit voltage and a current sensor for determining the inverter output current, the outputs of which are inputs to evaluating circuit, the output of which is connected to the control unit for the thyristors of the inverter, which evaluating circuit determines by means of a trigger pulse, prior to every zero crossing of the resonant circuit voltage, a firing instant for thyristors of diagonal bridge arms of the inverter, the position of which depends on the commutation time of the inverter and the protection time of the thyristors, the improvement comprising: a. the current sensor being one which measures and adds up to an ac current the currents in bridge arms with a common d-c terminal; and b. a monitoring circuit having as inputs the outputs of the current and the voltage sensor and developing at its output a pulse if, between a firing instant (t z ) and the corresponding zero crossing (t o ) of the resonant circuit voltage, the inverter output current and the resonant circuit voltage remain in phase or developing said pulse if said current and voltage are in phase opposition after the zero crossing.
Claim 3
Dependent Claim
44 words
The improvement according to claim 1, wherein said current sensor comprises a current transformer having primary windings coupled to the bridge arms of the inverter with a common d-c terminal, said windings coupled such that the current flows through the windings in opposite directions.
Claim 4
Dependent Claim
26 words
The improvement according to claim 1 and further including means for shutting down the inverter having its input coupled to the output of the monitoring circuit.
Claim 5
Dependent Claim
26 words
The improvement according to claim 1 wherein the output of the monitoring circuit is connected to a disabling input of the control unit of the inverter.
Claim 6
Dependent Claim
41 words
The improvement according to claim 1 wherein said monitoring circuit includes means for determining the relative phase of the resonant circuit voltage and the inverter output current only after the end of a predetermined time span, referred to the firing instant.
Claim 7
Dependent Claim
25 words
The improvement according to claim 5, wherein said time span is longer than the commutation and the protection time of the thyristors of said inverter.
Claim 8
Dependent Claim
26 words
The improvement according to claim 2 and further including means for shutting down the inverter having its input coupled to the output of the monitoring circuit.
Claim 9
Dependent Claim
26 words
The improvement according to claim 7 wherein the output of the monitoring circuit is connected to a disabling input of the control unit of the inverter.
Claim 10
Dependent Claim
41 words
The improvement according to claim 8 wherein said monitoring circuit includes means for determining the relative phase of the resonant circuit voltage and the inverter output current only after the end of a predetermined time span, referred to the firing instant.
Claim 11
Dependent Claim
41 words
The improvement according to claim 4 wherein said monitoring circuit includes means for determining the relative phase of the resonant circuit voltage and the inverter output current only after the end of a predetermined time span, referred to the firing instant.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-01-02 | 1981-07-04 | 1982-01-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-01-02 | 1985-07-04 | 1986-01-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-01-02 | 1989-07-04 | 1990-01-03 | $7700.00 | Window Closed / Lapsed |