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US3816808A
Expired / Lapsed
US
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Changing the frequency of a polyphase alternating current supply and apparatus therefor
Assignee: TIME MODULATION Ltd ZA Pty
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Filing: 1972-09-20
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Granted: 1974-06-11
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Expires: 1992-09-20
Abstract
Abstract A method of and an apparatus for controlling the frequency of a polyphase alternating current supply applied to a polyphase load. SCR''s or triacs are connected in matrices between each supply phase and each end of each load phase and selected sets thereof are made available for triggering in a predetermined stepping sequence. The current flow in the supply phases is monitored and when current zeros are detected in the supply phases the then available set of SCR''s or triacs are triggered. If desired, current zeros can be induced in the supply phases. The frequency applied to the load is controllable by varying the rate at which the sets of SCR''s or triacs are made available for triggering. The effective voltage applied to the load is also controllable by varying the time period between the detection of current zeros and the triggering of the sets of SCR''s or triacs.
Inventors
- 👤 Villiers Enslin N De
- 👤 J Chapman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 04:39
CPC Classifications
H; H02; H02M; H02M5/00; H02M5/02; H02M5/04; H02M5/22; H02M5/25; H02M5/27; H02M5/271
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
95 words
A method of controlling the frequency of a polyphase alternating current supply applied to a polyphase load which includes connecting an SCR or Triac Matrix between each supply phase and each end of each load phase; making selected sets of SCR''s or triacs in the matrices available for triggering in a predetermined cyclic stepping sequence; and monitoring current flow in the supply phases to detect current zeros in the supply phases and triggering the then available set of SCR''s or triacs in the matrices in a time period after the detection of said current zeros.
Claim 2
Independent Claim
95 words
A method of controlling the frequency of a polyphase alternating current supply applied to a polyphase load which includes connecting an SCR or Triac Matrix between each supply phase and each end of each load phase; making selected sets of SCR''s or triacs in the matrices available for triggering in a predetermined cyclic stepping sequence; and monitoring current flow in the supply phases to detect current zeros in the supply phases and triggering the then available set of SCR''s or triacs in the matrices in a time period after the detection of said current zeros.
Claim 3
Dependent Claim
18 words
A method as claimed in claim 1, which further includes selectively inducing current zeros in the supply phases.
Claim 4
Dependent Claim
29 words
A method as claimed in claim 1 in which the rate at which the sets of SCR''s or triacs are made available for triggering in succession is adjustably variable.
Claim 5
Dependent Claim
38 words
A method as claimed in claim 1, which further includes controllably varying the time period between the detection of the current zeros in the supply phases and the triggering of the then available set of SCR''s or triacs.
Claim 6
Dependent Claim
43 words
A method as claimed in claim 1, for controlling the frequency of a three phase alternating current supply, in which the sets of SCR''s or triacs are made available for triggering in fixed steps of sixty electrical degrees relative to the supply phases.
Claim 7
Dependent Claim
104 words
A frequency changer for controlling the frequency of a polyphase alternating current supply applied to a polyphase load, which includes an SCR or triac matrix connectable between each supply phase and each end of each load phase; monitoring means for detecting current zeros in the supply phases; and control means adapted to make selected sets of SCR''s or triacs in the matrices available for triggering in a predetermined cyclic stepping sequence and the control means being responsive to the monitoring means to trigger the then available set of SCR''s or triacs when current zeros are detected in the supply phases by the monitoring means.
Claim 8
Dependent Claim
104 words
A frequency changer for controlling the frequency of a polyphase alternating current supply applied to a polyphase load, which includes an SCR or triac matrix connectable between each supply phase and each end of each load phase; monitoring means for detecting current zeros in the supply phases; and control means adapted to make selected sets of SCR''s or triacs in the matrices available for triggering in a predetermined cyclic stepping sequence and the control means being responsive to the monitoring means to trigger the then available set of SCR''s or triacs when current zeros are detected in the supply phases by the monitoring means.
Claim 9
Dependent Claim
35 words
A frequency changer as claimed in claim 6, which further includes inhibiting means connectable in series with at least one of the supply phases and operable to induce current zeros in a particular supply phase.
Claim 10
Dependent Claim
45 words
A frequency changer as claimed in claim 6, which further includes a delay unit intermediate the monitoring means and the control means for controllably delaying the time period between the detection of the current zeros and the triggering of the sets of SCR''s or triacs.
Claim 11
Dependent Claim
24 words
A frequency changer as claimed in claim 8, in which the delay unit is adjustably variable to permit variation of the said time period.
Claim 12
Dependent Claim
32 words
A frequency changer as claimed in claim 6, in which the control means includes a stepping unit for making the sets of SCR''s or triacs in the matrices successively available for triggering.
Claim 13
Dependent Claim
34 words
A frequency changer as claimed in claim 10, in which the stepping unit is adjustable to permit adjustment of the rate at which the sets of SCR''s or triacs are made available for triggering.
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) | 1977-06-10 | 1977-12-10 | 1978-06-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-10 | 1981-12-10 | 1982-06-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-10 | 1985-12-10 | 1986-06-11 | $7700.00 | Window Closed / Lapsed |