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Patent US3860858A successfully refreshed from Google Patents.
US3860858A
Expired / Lapsed
US
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Variable frequency inverter for ac induction motors with torque, speed and braking control
Assignee: National Aeronautics and Space Administration
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Filing: 1973-12-19
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Granted: 1975-01-14
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Expires: 1993-12-19
Abstract
Abstract A variable frequency inverter for driving an AC induction motor which varies the frequency and voltage to the motor windings in response to varying torque requirements for the motor so that the applied voltage amplitude and frequency are of optimal value for any motor load and speed requirement. The slip frequency of the motor is caused to vary proportionally to the torque and feedback is provided so that the most efficient operating voltage is applied to the motor. Winding current surge is limited and a controlled negative slip causes motor braking and return of load energy to a DC power source.
Inventors
- 👤 Frank J Nola
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 21:51
CPC Classifications
H; H02; H02P; H02P27/00; H02P27/04; H02P27/06; H02P27/08; H02P27/045; H02P27/048; H02P2207/00; H02P2207/01; H02P27/047
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
183 words
A variable frequency inverter for controlling the operation of an AC induction motor powered by a DC source, comprising: a summing amplifier which provides a DC output which is the sum of at least two DC inputs; a DC amplifier having a DC speed input command signal applied to its input terminal and having its output signal connected to said summing amplifier to provide one of said inputs; means responsive to the shaft speed of said motor for generating a DC speed proportional voltage and for applying said voltage to said DC amplifier input terminal and to said summing amplifier to provide another of said inputs; a voltage controlled oscillator connected to said summing amplifier output to be controlled thereby; means for multiplying the output of said voltage controlled oscillator with said DC amplifier output signal; means for receiving the output of said multiplying means and for generating a pulse train in response thereto; switching means for switchably connecting a winding of said motor to said DC source; and, switch control means for controlling said switching means in response to said pulse train.
Claim 2
Dependent Claim
183 words
A variable frequency inverter for controlling the operation of an AC induction motor powered by a DC source, comprising: a summing amplifier which provides a DC output which is the sum of at least two DC inputs; a DC amplifier having a DC speed input command signal applied to its input terminal and having its output signal connected to said summing amplifier to provide one of said inputs; means responsive to the shaft speed of said motor for generating a DC speed proportional voltage and for applying said voltage to said DC amplifier input terminal and to said summing amplifier to provide another of said inputs; a voltage controlled oscillator connected to said summing amplifier output to be controlled thereby; means for multiplying the output of said voltage controlled oscillator with said DC amplifier output signal; means for receiving the output of said multiplying means and for generating a pulse train in response thereto; switching means for switchably connecting a winding of said motor to said DC source; and, switch control means for controlling said switching means in response to said pulse train.
Claim 3
Dependent Claim
30 words
The variable frequency inverter of claim 1 wherein said pulse train generating means generates pulses the width of which is related to the amplitude of said DC amplifier output signal.
Claim 4
Dependent Claim
34 words
The variable frequency inverter of claim 2 further including: a resistor connected in series with said motor winding; and, means for connecting said resistor to said multiplier output receiving means in a feedback configuration.
Claim 5
Dependent Claim
80 words
The variable frequency inverter of claim 2 further including: a second means for multiplying the output of said voltage controlled oscillator with said DC amplifier output signal; means for receiving the output of said second multiplying means and for generating a second pulse train in response thereto; switching means for switchably connecting a second winding of said motor to said DC source; and, switch control means for controlling said second winding switching means in response to said second pulse train.
Claim 6
Dependent Claim
55 words
The variable frequency inverter of claim 4 wherein: said voltage controlled oscillator has a first sinuosoid output and a second sinusoid output 90* out of phase with said first sinusoid output; said multiplying means is connected to receive said first sinusoid output; and, said second multiplying means is connected to receive said second sinusoid output.
Claim 7
Dependent Claim
28 words
The variable frequency inverter of claim 3 wherein said pulse train generating means generates pulses the width of which is related to the current passing through said resistor.
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) | 1978-01-13 | 1978-07-15 | 1979-01-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-01-13 | 1982-07-15 | 1983-01-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-01-13 | 1986-07-15 | 1987-01-14 | $7700.00 | Window Closed / Lapsed |