US3725768A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Current fed inverter circuit using the time sharing principle
Assignee: Westinghouse Electric Corp
•
Filing: 1971-06-07
•
Granted: 1973-04-03
•
Expires: 1991-06-07
Abstract
Abstract A current fed inverter circuit operating in a time-sharing mode to supply A.C. output voltage to a load from a D.C. voltage source. Typically the load may be inductive, for example, an induction heating work coil, in which case a capacitor is connected across it to correct the power factor. So-called ''''time-sharing'''' capacitors are connected in series between the solid state switching devices of the inverter circuit, which are typically thyristors, and the electrical load. Under all output voltage conditions up to and including the preferred full load voltage operating condition the phase displacement between the output voltage and output current is such that the current always lags the voltage thus establishing a lagging phase angle operation. The time-sharing capacitors under ideal conditions are dimensioned such that with the full load current flowing at the output of the inverter circuit, the peak voltage developed across each time-sharing capacitor is approximately equal to the peak load voltage at the normal output frequency.
Inventors
- 👤 B Pelly
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:30
CPC Classifications
H; H02; H02M; H02M7/00; H02M7/42; H02M7/44; H02M7/48; H02M7/505; H02M7/515; H02M7/523
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
179 words
A power inverter apparatus operatively connected between a D.C. input voltage source and output circuit to supply an A.C. output voltage to said output circuit, comprising, an inverter power stage, means operatively connected between said D.C. input voltage source and said inverter power stage to supply substantially smooth direct current to said inverter power stage, said inverter power stage including a plurality of ON-OFF conduction controlled power switching devices for developing a continuous output current flow in alternate directions through said output circuit in response to a prescribed sequence of power switching device firing signals, control circuit means for generating said sequence of firing signals to operate each of said power switching devices at a fundamental frequency of operation which is a sub-multiple of the frequency of said A.C. output voltage, and time-sharing capacitors operatively connected in series between said power switching devices and said output circuit, said time-sharing capacitors maintaining a reverse bias across each power switching device following conduction thereof for a period of time sufficient to insure turn off of each of said power switching devices.
Claim 2
Dependent Claim
179 words
A power inverter apparatus operatively connected between a D.C. input voltage source and output circuit to supply an A.C. output voltage to said output circuit, comprising, an inverter power stage, means operatively connected between said D.C. input voltage source and said inverter power stage to supply substantially smooth direct current to said inverter power stage, said inverter power stage including a plurality of ON-OFF conduction controlled power switching devices for developing a continuous output current flow in alternate directions through said output circuit in response to a prescribed sequence of power switching device firing signals, control circuit means for generating said sequence of firing signals to operate each of said power switching devices at a fundamental frequency of operation which is a sub-multiple of the frequency of said A.C. output voltage, and time-sharing capacitors operatively connected in series between said power switching devices and said output circuit, said time-sharing capacitors maintaining a reverse bias across each power switching device following conduction thereof for a period of time sufficient to insure turn off of each of said power switching devices.
Claim 3
Dependent Claim
45 words
A power inverter apparatus as claimed in claim 1 wherein said output circuit means includes an electrical load which is substantially inductive to the fundamental frequency of said A.C. output voltage and exhibits a relatively low impedance to high order harmonics of said output current.
Claim 4
Dependent Claim
25 words
A power inverter apparatus as claimed in claim 2 wherein said output circuit means includes a shunting capacitor connected in parallel across said electrical load.
Claim 5
Dependent Claim
49 words
A power inverter apparatus as claimed in claim 1 wherein said time sharing capacitors are dimensioned such that the output current flow under full load conditions results in a peak voltage developed across each time sharing capacitor which corresponds substantially to the peak voltage developed across said output circuit.
Claim 6
Dependent Claim
28 words
A power inverter apparatus as claimed in claim 1 wherein said means for supplying substantially smooth direct current to said inverter power stage includes a current smoothing inductor.
Claim 7
Dependent Claim
261 words
A power inverter apparatus operatively connected between a D.C. input voltage source and an output circuit to supply an A.C. output voltage to said output circuit, comprising, an inverter power stage, inductor means operatively connected between said D.C. input voltage source and said inverter power stage to supply substantially smooth direct current to said inverter power stage, said inverter power stage including a plurality of ON-OFF conduction controlled power switching devices for developing a continuous output current flow in alternate directions through said output circuit in response to a prescribed sequence of power switching device firing signals, wherein said output circuit means includes an electrical load which is substantially inductive to the fundamental frequency of said A.C. output voltage and exhibits a relatively low impedance to high order harmonics of said input current, control circuit means for generating said sequence of firing signals to operate each of said power switching devices at a fundamental frequency of operation which is a submultiple of the frequency of said A.C. output voltage, and time sharing capacitors operatively connected in series between saiD power switching devices and said output circuit, said time sharing capacitors maintaining a reverse bias across each power switching device following conduction thereof for a period of time sufficient to insure turn-off of each of said power switching devices, wherein said control circuit means includes a firing angle control circuit means for adjusting the firing angle of said power switching devices in response to variations in said electrical load to maintain an essentially constant turn off time for said power switching devices.
Claim 8
Dependent Claim
261 words
A power inverter apparatus operatively connected between a D.C. input voltage source and an output circuit to supply an A.C. output voltage to said output circuit, comprising, an inverter power stage, inductor means operatively connected between said D.C. input voltage source and said inverter power stage to supply substantially smooth direct current to said inverter power stage, said inverter power stage including a plurality of ON-OFF conduction controlled power switching devices for developing a continuous output current flow in alternate directions through said output circuit in response to a prescribed sequence of power switching device firing signals, wherein said output circuit means includes an electrical load which is substantially inductive to the fundamental frequency of said A.C. output voltage and exhibits a relatively low impedance to high order harmonics of said input current, control circuit means for generating said sequence of firing signals to operate each of said power switching devices at a fundamental frequency of operation which is a submultiple of the frequency of said A.C. output voltage, and time sharing capacitors operatively connected in series between saiD power switching devices and said output circuit, said time sharing capacitors maintaining a reverse bias across each power switching device following conduction thereof for a period of time sufficient to insure turn-off of each of said power switching devices, wherein said control circuit means includes a firing angle control circuit means for adjusting the firing angle of said power switching devices in response to variations in said electrical load to maintain an essentially constant turn off time for said power switching devices.
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) | 1976-04-02 | 1976-10-02 | 1977-04-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-02 | 1980-10-02 | 1981-04-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-02 | 1984-10-02 | 1985-04-03 | $7700.00 | Window Closed / Lapsed |