US3767987A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control apparatus for an induction motor
Assignee: Hitachi Ltd
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Filing: 1972-03-20
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Granted: 1973-10-23
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Expires: 1992-03-20
Abstract
Abstract A control apparatus for an induction motor comprising a three phase induction motor, a three phase alternating current source for supplying a three phase alternating current voltage for the induction motor, parallel thyristors connected in the reverse direction to each other and inserted in an arbitrary phase of the three phase alternating current source for controlling the current flowing therethrough, contactors for changing the main circuit of the induction motor so as to reverse the direction of the phase rotation of the alternating current voltage when the induction motor is in a single phase operation by control of the thyristors, and a control device for operating the thyristors to substantially eliminate the current flowing therethrough in response to a reduction command and to increase the current again when the contactors complete changing the main circuit.
Inventors
- 👤 N Mitsui
- 👤 A Watanabe
- 👤 K Komuro
- 👤 T Hatakeyama
- 👤 K Numata
- 👤 I Fukushima
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 19:07
CPC Classifications
H; H02; H02P; H02P3/00; H02P3/06; H02P3/18; H02P3/20; B; B66; B66B; B66B1/00; B66B1/24; B66B1/28; B66B1/30; B66B1/308
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
156 words
A control apparatus for controlling the operation of a three phase induction motor from a three phase alternating current source connected to said motor, comprising variable impedance means inserted in the line carrying one selected phase of said three phase alternating current source to said motor for controlling the current flowing therethrough, control means for operating said impedance means to substantially eliminate the current flowing therethrough in response to a speed reduction command, means for producing an output signal when said motor is in single phase operation due to control by said impedance means, switching means for switching the lines of said source connected to said motor so as to reverse the direction of the three phase rotation of said alternating current voltage in response to said output signal, and further means for controlling said impedance means to increase said current therethrough in response to said switching means completing the reversing of said three phase rotation.
Claim 2
Dependent Claim
156 words
A control apparatus for controlling the operation of a three phase induction motor from a three phase alternating current source connected to said motor, comprising variable impedance means inserted in the line carrying one selected phase of said three phase alternating current source to said motor for controlling the current flowing therethrough, control means for operating said impedance means to substantially eliminate the current flowing therethrough in response to a speed reduction command, means for producing an output signal when said motor is in single phase operation due to control by said impedance means, switching means for switching the lines of said source connected to said motor so as to reverse the direction of the three phase rotation of said alternating current voltage in response to said output signal, and further means for controlling said impedance means to increase said current therethrough in response to said switching means completing the reversing of said three phase rotation.
Claim 3
Dependent Claim
94 words
A control apparatus for an induction motor according to claim 1 wherein said control means comprising reference means for producing a reference voltage which starts to increase simultaneously with the start of said motor, decreases in Response to a reduction command for said motor and recovers to a selected value after a predetermined time after the current of said selected one phase becomes substantially zero while said motor is in operation, and means for controlling said variable impedance means in accordance with the difference between said reference voltage and the speed of said motor.
Claim 4
Dependent Claim
37 words
A control apparatus for an induction motor according to claim 1 wherein said producing means comprises a first relay excited when the current of said selected one phase becomes substantially zero while said motor is in operation.
Claim 5
Dependent Claim
68 words
A control apparatus for an induction motor according to claim 2 wherein said reference means comprises a second relay excited in response to said reduction command and released after said predetermined time after the current of said selected one phase becomes substantially zero while said motor is in operation, and a condensor circuit repeating a charge and a discharge thereof according to the operation of said second relay.
Claim 6
Dependent Claim
32 words
A control apparatus for an induction motor according to claim 2 wherein said predetermined time is a period long enough to reverse said phase of rotation by means of said switching means.
Claim 7
Dependent Claim
177 words
A control apparatus for controlling the operation of a three phase induction motor selectively connected to a three phase alternating current source by way of three individual phase lines, comprising first relay means having contacts in each of said three phase lines for selectively connecting said alternating current source to said induction motor, second relay means having contacts in only a first and a second line of said three phase lines for selectively disconnecting said lines from said induction motor, third relay means having a contact connecting said first phase line to said second phase line and another contact connecting said second phase line to said first phase line for reversing the connections of said first and second phase lines to said induction motor, and variable impedance means connected in a third line of said three phase lines to control the current flowing therein, said second and third relay means being responsive to a predetermined condition of the current in said third line controlled by said variable impedance means for respectively opening and closing the contacts thereof.
Claim 8
Dependent Claim
177 words
A control apparatus for controlling the operation of a three phase induction motor selectively connected to a three phase alternating current source by way of three individual phase lines, comprising first relay means having contacts in each of said three phase lines for selectively connecting said alternating current source to said induction motor, second relay means having contacts in only a first and a second line of said three phase lines for selectively disconnecting said lines from said induction motor, third relay means having a contact connecting said first phase line to said second phase line and another contact connecting said second phase line to said first phase line for reversing the connections of said first and second phase lines to said induction motor, and variable impedance means connected in a third line of said three phase lines to control the current flowing therein, said second and third relay means being responsive to a predetermined condition of the current in said third line controlled by said variable impedance means for respectively opening and closing the contacts thereof.
Claim 9
Dependent Claim
38 words
A control apparatus according to claim 6, further including control means responsive to a speed reduction command for operating said variable impedance means to gradually eliminate the current flowing in the third line of said three phase lines.
Claim 10
Dependent Claim
65 words
A control apparatus according to claim 7, further including current sensing means for detecting a zero current condition in said third line of said three phase lines, said second relay means being responsive to said current sensing means to open its contacts and said third relay means being responsive to said current sensing means to close its contacts when said zero current condition is detected.
Claim 11
Dependent Claim
39 words
A control apparatus according to claim 8, further including timing means for releasing said control means to control said variable impedance means to gradually increase the current in said third line of said three phase lines to rated value.
Claim 12
Dependent Claim
36 words
A control apparatus according to claim 9 wherein said impedance means includes a pair of reversely connected thyristors and said control means includes a capacitor charging circuit connected to said thyristors for controlling the conduction thereof.
Claim 13
Independent Claim
87 words
A method for stopping a three phase induction motor operating from a three phase alternating current source comprising the steps of switching said three phase current to a single phase current to initiate stopping said motor while providing essentially the same motor torque as in the three phase alternating current operation of the motor, reversing two of said phases of alternating current from said source, and gradually converting said single phase alternating current to said reversed Three phase alternating current to produce a stopping of said motor.
Claim 14
Independent Claim
87 words
A method for stopping a three phase induction motor operating from a three phase alternating current source comprising the steps of switching said three phase current to a single phase current to initiate stopping said motor while providing essentially the same motor torque as in the three phase alternating current operation of the motor, reversing two of said phases of alternating current from said source, and gradually converting said single phase alternating current to said reversed Three phase alternating current to produce a stopping of said motor.
Claim 15
Dependent Claim
26 words
A method as defined in claim 11 wherein said switching step is performed by opening one of the three phase lines from said alternating current source.
Claim 16
Dependent Claim
26 words
A method as defined in claim 12 wherein said one of the three phase lines is opened by operating a switching device connected in the line.
Claim 17
Independent Claim
129 words
A method for controlling the operation of a three phase induction motor from a three phase alternating current source comprising the steps of applying to said induction motor initially a single phase alternating current from said alternating current source, gradually converting said single phase alternating current to a three phase alternating current to produce progressive starting of said induction motor until full rated current is applied thereto, operating said motor at full rated three phase current from said alternating current source, switching said three phase current to a single phase current to initiate stopping said motor, reversing two of said phases of alternating current from said source, and gradually converting said single phase alternating current to said reversed three phase alternating current to produce a stopping of said motor.
Claim 18
Independent Claim
129 words
A method for controlling the operation of a three phase induction motor from a three phase alternating current source comprising the steps of applying to said induction motor initially a single phase alternating current from said alternating current source, gradually converting said single phase alternating current to a three phase alternating current to produce progressive starting of said induction motor until full rated current is applied thereto, operating said motor at full rated three phase current from said alternating current source, switching said three phase current to a single phase current to initiate stopping said motor, reversing two of said phases of alternating current from said source, and gradually converting said single phase alternating current to said reversed three phase alternating current to produce a stopping of said motor.
Claim 19
Dependent Claim
26 words
A method as defined in claim 14 wherein said switching step is performed by opening one of the three phase lines from said alternating current source.
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) | 1976-10-22 | 1977-04-23 | 1977-10-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-22 | 1981-04-23 | 1981-10-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-22 | 1985-04-23 | 1985-10-23 | $7700.00 | Window Closed / Lapsed |