US3581172A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control system of electric motor
Assignee: Hitachi Ltd
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Filing: 1969-04-01
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Granted: 1971-05-25
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Expires: 1989-04-01
Abstract
Abstract A control system for electric motors effecting variation of the electric motor current in a step-by-step operation in successive stages, second impedance control means for controlling the variation of said current by said first means in a linear fashion by providing an impedance varying from a minimum value to a maximum value during each stage of operation and control means for effecting a transition of first means from one stage to the next in response to detection of said motor current reaching a predetermined value and simultaneously changing the impedance of said second means to said maximum value.
Inventors
- 👤 Takashi Tsuboi
- 👤 Hiroshi Narita
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 11:34
CPC Classifications
H; H02; H02P; H02P3/00; H02P3/06; H02P3/08; H02P3/12
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
277 words
A control system for electric motors comprising: first means connected to an electric motor for changing the electric motor current in a plurality of successive control stages of operation in a step-by-step manner; second means connected to said first means for converting the current change of the electric motor by said first means to a substantially linear variation over a prescribed range for each control stage of operation by variation of the impedance thereof; control means for controlling the impedance of said second means within said prescribed range, including signal means of said second means within said prescribed range, including signal means for supplying alternately to said second means; a first signal for reducing the impedance of said second means to a relatively low impedance state and a second signal for increasing the impedance of said second means to a relatively high impedance state, means for varying the interval between said first and second signals to correspond to the deviation of the actual motor current value from a reference current value and actuating means for actuating said first means to effect a transition into the next control stage of operation when the interval between said first and said second signals reaches a predetermined value; auxiliary control means responsive to said actuating means for controlling the impedance of said second means during transition of said first means from one control stage to the next control stage, including interrupting means for interrupting said first signal being supplied to said second means from said control means and impedance control means for switching the impedance of said second means to said relatively high impedance state during the duration of said transition.
Claim 2
Dependent Claim
277 words
A control system for electric motors comprising: first means connected to an electric motor for changing the electric motor current in a plurality of successive control stages of operation in a step-by-step manner; second means connected to said first means for converting the current change of the electric motor by said first means to a substantially linear variation over a prescribed range for each control stage of operation by variation of the impedance thereof; control means for controlling the impedance of said second means within said prescribed range, including signal means of said second means within said prescribed range, including signal means for supplying alternately to said second means; a first signal for reducing the impedance of said second means to a relatively low impedance state and a second signal for increasing the impedance of said second means to a relatively high impedance state, means for varying the interval between said first and second signals to correspond to the deviation of the actual motor current value from a reference current value and actuating means for actuating said first means to effect a transition into the next control stage of operation when the interval between said first and said second signals reaches a predetermined value; auxiliary control means responsive to said actuating means for controlling the impedance of said second means during transition of said first means from one control stage to the next control stage, including interrupting means for interrupting said first signal being supplied to said second means from said control means and impedance control means for switching the impedance of said second means to said relatively high impedance state during the duration of said transition.
Claim 3
Dependent Claim
36 words
A control system for electric motors according to claim 1, wherein said first means includes a plurality of impedance sections connected in series, and contactor means connected to respective impedance sections for selectively short-circuiting said sections.
Claim 4
Dependent Claim
61 words
A control system for electric motors according to claim 2, wherein said second means includes a switching circuit whose operation is controlled by said control means to effect an alternation between the conductive state and the nonconductive state thereof and an additional impedance section connected in series with said plurality of impedance sections and connected in parallel with said switching circuit.
Claim 5
Dependent Claim
90 words
A control system for electric motors according to claim 3, wherein said switching circuit comprises: a first thyristor connected across said additional impedance section in the direction of flow of said motor current therethrough; and commutating means for commutating the current flow through said first thyristor including a second thyristor connected in parallel to said first thyristor, a diode connected between the anodes of said first and second thyristors, and resonance means connected in parallel to said second thyristor in the form of an inductive element and a capacitive element.
Claim 6
Dependent Claim
95 words
A control system for electric motors according to claim 3, wherein said control means which controls said switching means comprises: an oscillator generating a reCtangular wave voltage, a phase shifter which shifts the phase of said rectangular wave voltage generated by said oscillator in response to a signal representing the deviation of the actual motor current value from the reference current value applied to the input thereof; and a first pulse forming circuit which differentiates the rising and falling portions, respectively, of the phase shifted rectangular wave to form said first and said second signals.
Claim 7
Dependent Claim
26 words
A control system for electric motors according to claim 5, wherein said input to said phase shifter is short circuited during the duration of said transition.
Claim 8
Dependent Claim
78 words
A control system for electric motors according to claim 3, wherein impedance control means in said auxiliary control means including auxiliary means for applying to said switching circuit a third signal for increasing the impedance of said second means to said relatively high impedance state as soon as the transition is entered, and wherein said interrupting means serves to simultaneously interrupt said first and said second signals supplied by said control means during the duration of said transition.
Claim 9
Dependent Claim
50 words
A control system for electric motors according to claim 7, wherein said auxiliary means includes a differentiation circuit, said interrupting means being formed by a relay selectively connecting said differentiating circuit to a DC voltage source so as to selectively generate said third signal upon actuation of said interrupting means.
Claim 10
Dependent Claim
55 words
A control system for electric motors according to claim 3, wherein said impedance control means in said auxiliary control means includes auxiliary means for alternately supplying to said switching circuit third and fourth signals spaced to maintain the impedance of said second means at said relatively low impedance state during the duration of said transition.
Claim 11
Dependent Claim
64 words
A control system for electric motors according to claim 9, wherein said auxiliary means comprises: an oscillator generating a rectangular wave voltage, a fixed phase shifter for shifting the phase of said rectangular wave voltage generated by said oscillator to a predetermined degree; and a second pulse forming circuit which differentiates the phase shifted rectangular wave to form said third and said fourth signals.
Claim 12
Dependent Claim
84 words
A control system for electric motors according to claim 3, wherein said impedance control means in said auxiliary control means includes auxiliary means for applying to said switching circuit a third signal for increasing the impedance of said second means to said relatively high impedance state as soon as the transition is entered, and alternately to said switching circuit fourth and fifth signals spaced to maintain the impedance of said second means at said relatively low impedance state during the duration of the transition.
Claim 13
Dependent Claim
64 words
A control system for electric motors according to claim 2, wherein each of said contactor means comprises a saturable reactor, said saturable reactors being coupled to said impedance sections so as to detect the closing of the contactor of the respective contactor means, the output of each saturable reactors being employed to actuate said auxiliary control means at the time of entrance into transition.
Claim 14
Dependent Claim
50 words
A control system for electric motors according to claim 12, wherein all of said saturable reactors are formed on a common iron core, the currents from said impedance sections due to closing of said contactor means serving to induce magnetic flux with alternately reversed polarities successively in said iron core.
References Cited (Backward Citations)
US3299347A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-05-24 | 1974-11-23 | 1975-05-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-05-24 | 1978-11-23 | 1979-05-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-05-24 | 1982-11-23 | 1983-05-25 | $7700.00 | Window Closed / Lapsed |