US4481456A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Microprocessor controlled multifrequency AC converter
Assignee: RTX Corp
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Filing: 1983-01-24
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Granted: 1984-11-06
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Expires: 2003-01-24
Abstract
Abstract An AC converter changes the frequency of an incoming voltage waveform to operate an induction motor driving a ventilation system at one or several different speeds. A program followed by a microprocessor utilizes the phase-to-phase incoming voltage waveform in a step-by-step sequence to generate control signals for the switches in a switching matrix. A full-speed subroutine, a three-quarter speed subroutine and a half-speed subroutine are disclosed for the microprocessor.
Inventors
- 👤 Russell G. Meyerand, Jr.
- 👤 Louis L. Daigle
- 👤 Donald C. Paine
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 02:03
CPC Classifications
H; H02; H02P; H02P27/00; H02P27/04; H02P27/06; H02P23/00; H02P23/0077
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
164 words
A converter for transforming a three-phase, sinusoidal waveform of a first frequency directly to a lower frequency waveform having a substantially sinusoidal characteristic for operating an AC motor comprising: input means from a source of electrical energy, for receiving electrical power having a plurality of phases; switching means including a matrix having a plurality of switching elements connected between said source of electrical energy and said motor; sensing means for monitoring the phase of the voltage waveforms from said source of electrical energy; processing means for selectively operating said motor in a number of different speed modes, said processing means following a step-by-step program sequence to determine equality between selected phases of said three-phase sinusoidal waveform, and to generate control signals that enable each of said switching elements of said switching means at a predetermined time and in a particular sequence; and whereby said converter presents said lower frequency waveform to said motor allowing operation at either full speed, three-quarter speed or half speed.
Claim 2
Dependent Claim
164 words
A converter for transforming a three-phase, sinusoidal waveform of a first frequency directly to a lower frequency waveform having a substantially sinusoidal characteristic for operating an AC motor comprising: input means from a source of electrical energy, for receiving electrical power having a plurality of phases; switching means including a matrix having a plurality of switching elements connected between said source of electrical energy and said motor; sensing means for monitoring the phase of the voltage waveforms from said source of electrical energy; processing means for selectively operating said motor in a number of different speed modes, said processing means following a step-by-step program sequence to determine equality between selected phases of said three-phase sinusoidal waveform, and to generate control signals that enable each of said switching elements of said switching means at a predetermined time and in a particular sequence; and whereby said converter presents said lower frequency waveform to said motor allowing operation at either full speed, three-quarter speed or half speed.
Claim 3
Dependent Claim
46 words
A converter according to claim 1, wherein said input menas receives electrical energy from a three-phase source, and wherein said processing means follows a program that utilizes the amplitudes of the incoming voltage waveform as a reference point to provide enable signals to said switching means.
Claim 4
Dependent Claim
40 words
A converter according to claim 1, wherein the processing means follows a step-by-step program enabling selected ones of said plurality of switching elements in said switching means to operate said motor at either full speed, three-quarter speed or half speed.
Claim 5
Dependent Claim
95 words
A converter according to claim 1, wherein said switching means includes a plurality of thyristors connected between said input means and said motor, and wherein each of said thyristors includes a control terminal through which said thyristors can be enabled by presentation of a suitable control signal, and wherein said processing means includes a plurality of output ports, one of which is connected to each of said gate terminals, and wherein said processing means follows either a full-speed subroutine, a three-quarter speed subroutine or a half-speed subroutine to enable three selected ones of said thyristors.
Claim 6
Dependent Claim
27 words
A converter according to claim 1, wherein said processing means follows each determination of equality with a predetermined period of delay before generating a particular control signal.
Claim 7
Dependent Claim
14 words
A converter according to claim 5, wherein said delay period is approximately four milliseconds.
Claim 8
Dependent Claim
14 words
A converter according to claim 5, wherein said delay period is approximately 5.5 milliseconds.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-11-06 | 1988-05-07 | 1988-11-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-11-06 | 1992-05-07 | 1992-11-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-11-06 | 1996-05-07 | 1996-11-06 | $7700.00 | Window Closed / Lapsed |