US3753002A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Synchronizing and transfer system
Assignee: GEC AUTOMATION PROJECTS Inc
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Filing: 1972-05-05
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Granted: 1973-08-14
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Expires: 1992-05-05
Abstract
Abstract A synchronizing and transfer system enabling a fully loaded induction motor to be switched from or to a variable frequency converter having a quasi-square wave voltage, to or from a line having a sine wave voltage. Upon the motor to be transferred reaching a full-speed condition, the system senses the frequency and phase angle difference between the converter output and line and acts upon the converter frequency to decrease the difference. When the frequency and phase angle differences are within preset limits, load transfer switching is initiated. During the course of load transfer, an inductive impedance is transiently inserted in series with each phase of the converter output for a period of parallel feed, the impedance acting to prevent excessive cross currents from damaging the converter.
Inventors
- 👤 E Jacobson
- 👤 D Schlicher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 19:18
CPC Classifications
H; H02; H02J; H02J3/00; H02J3/38; H02J3/40; H02J3/42
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
154 words
A synchronizing and transfer system enabling a fully loaded induction motor to be switched from or to a variable frequency converter to or from a line having a sine wave voltage, comprising in combination: a. a variable frequency converter; b. a source of line power having a sinuSoidal potential waveform; c. at least one induction motor; d. switching means operative to transfer said induction motor between said converter output and said line output; and e. synchronization and matching means connected to said line power source to said converter and to said switching means, for sensing the phase relationship between the respective waveforms of said line and converter and the rate of slip of said waveforms with respect to one another, said means being adapted to provide an output to said switching means for activating said transfer of said induction motor upon sensing of selected phase and slip rate conditions between said respective wave forms.
Claim 2
Dependent Claim
154 words
A synchronizing and transfer system enabling a fully loaded induction motor to be switched from or to a variable frequency converter to or from a line having a sine wave voltage, comprising in combination: a. a variable frequency converter; b. a source of line power having a sinuSoidal potential waveform; c. at least one induction motor; d. switching means operative to transfer said induction motor between said converter output and said line output; and e. synchronization and matching means connected to said line power source to said converter and to said switching means, for sensing the phase relationship between the respective waveforms of said line and converter and the rate of slip of said waveforms with respect to one another, said means being adapted to provide an output to said switching means for activating said transfer of said induction motor upon sensing of selected phase and slip rate conditions between said respective wave forms.
Claim 3
Dependent Claim
42 words
A system in accordance with claim 1, wherein said switching means includes transfer initiating means adapted upon external activation to provide a signal to said synchronization and matching means for activating said synchronization and matching means thereby to effect said power transfer.
Claim 4
Independent Claim
79 words
A system in accordance with claims 1 further including an inductive impedance insertable between the output of said converter and said motor, and means to insert said inductive impedance while maintaining a transient period of parallel feed to said induction motor from both said converter and said line power source during said transfer of said motor, said impedance acting to hold cross currents between converter and line power to tolerable levels while the said motor is connected to both.
Claim 5
Dependent Claim
47 words
A system according to claim 3 further including means for generating a frequency correcting signal for application in feed back relationship to said converter to thereby alter the converter frequency output in a direction tending to diminish the phase differences between said converter and line power source.
Claim 6
Dependent Claim
14 words
A system according to claim 4, wherein said converter has a quasi-square waveform output.
Claim 7
Dependent Claim
32 words
A system in accordance with claim 5, including a plurality of said induction motors, said switching means being operative to transfer successive of said motors between said converter and said line output.
Claim 8
Dependent Claim
84 words
A system in accordance with claim 5, wherein said synchronization and matching means includes means for generating the first pulse of predetermined width having a fixed relationship to the phase of the said line power waveform, means for generating a second pulse of predetermined width having a fixed relationship to the phase of said converter waveform, and means providing an output upon simultaneous presence of said first and second pulses, said output indicating appropriate phasing conditions between said two waveforms for initiating said transfer.
Claim 9
Dependent Claim
123 words
A system according to claim 7, wherein said synchronization and matching means further includes means for generating third and fourth pulses of predetermined width respectively following and first and second pulses, said third and fourth pulses being provided to means connected to receive a pair of reference pulses having a fixed phase relationship to said converter and line waveforms and provide an enabling output during the occurrence of a reference pulse and the associated third or fourth pulse; and timing circuit means connected to receive said enabling output and provide a slip signal upon the occurrence of said enabling output for a predetermined period, said slip signal being thereby indicative of an acceptable rate of slip between said converter and line power waveforms.
Claim 10
Dependent Claim
46 words
A system according to claim 8 wherein said slip signal and said output indicative of appropriate phasing are applied to an AND gate, the output of which activates said switching means, whereby said switching means is enabled upon the occurrence of acceptable phasing and slip conditions.
Claim 11
Dependent Claim
177 words
A system according to claim 9 wherein said means for generating a frequency correcting signal includes first and second latches respectively turned on by reference signals derived from selected phase point on said line power and converter waveform outputs respectively, whereby one Of said latches is activated when said converter waveform lags with respect to said line waveform and the other of said latches is activated when said converter waveform leads with respect to said line waveform; lockout means being provided between said first and second latches for locking out the alternate latch upon activation of one of said latches; said latches having latch outputs connected to an output amplifier adapted to provide a correcting signal to said converter in a direction tending to correct the lag or lead in said frequency output; said latches being connected to turn off upon occurrence of a reference signal in the alternate waveform from that turning said latch on, whereby the said correcting signal has a limited duration representing a function of the said lag or lead between said waveforms.
Claim 12
Dependent Claim
84 words
A system in accordance with claim 10 wherein said reference signals are provided to said latches through a pair of OR gates, the other set of inputs for said OR gates being provided by a feedback loop present between said latches and said OR gates, said feedback loop including a timing circuit for delaying said feedback signal, said loop acting to reset said latches following a predetermined period after enabling thereof, whereby said signal to said output amplifier is limited to a predetermined duration.
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) | 1976-08-13 | 1977-02-12 | 1977-08-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-13 | 1981-02-12 | 1981-08-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-13 | 1985-02-12 | 1985-08-14 | $7700.00 | Window Closed / Lapsed |