Patent US3571693A successfully refreshed from Google Patents.
US3571693A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Constant frequency output two-stage induction machine systems
Assignee: National Aeronautics and Space Administration
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Filing: 1968-11-21
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Granted: 1971-03-23
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Expires: 1988-11-21
Abstract
Abstract A system employing double-induction machines and being capable of providing constant-frequency electrical power from a variable speed drive or of operating as a controlled speed motor from a constant-frequency source. The disclosed system employs two polyphase, wound-rotor induction machines mounted on the same shaft and having their rotor windings connected in a reverse phase sequence and their stator windings interconnected by means of a direct-current link-type of static frequency changer.
Inventors
- 👤 Mahmoud Riaz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 12:04
CPC Classifications
H; H02; H02K; H02K17/00
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
149 words
An induction machine system comprising: a first induction machine having a rotor and polyphase rotor winding associated therewith, said first machine also having a stator winding: a second induction machine having a rotor and polyphase rotor winding associated therewith, said second machine also having a stator winding; a second induction machine having a rotor and polyphase rotor winding associated therewith, said second machine also having a stator winding; means mounting said first and second machine rotors for rotation with the same shaft; means interconnecting said first and second machine rotor windings in reverse phase sequence; frequency changer means including a rectifier for connecting the stator winding of said second machine to the stator winding of said first machine; and means connecting said first machine stator winding and the output of said frequency changer to a polyphase transmission line whereby power may be delivered to or taken from said system.
Claim 2
Dependent Claim
149 words
An induction machine system comprising: a first induction machine having a rotor and polyphase rotor winding associated therewith, said first machine also having a stator winding: a second induction machine having a rotor and polyphase rotor winding associated therewith, said second machine also having a stator winding; a second induction machine having a rotor and polyphase rotor winding associated therewith, said second machine also having a stator winding; means mounting said first and second machine rotors for rotation with the same shaft; means interconnecting said first and second machine rotor windings in reverse phase sequence; frequency changer means including a rectifier for connecting the stator winding of said second machine to the stator winding of said first machine; and means connecting said first machine stator winding and the output of said frequency changer to a polyphase transmission line whereby power may be delivered to or taken from said system.
Claim 3
Dependent Claim
49 words
The apparatus of claim 1 wherein said frequency changer comprises: a rectifier connected to the stator winding of said second machine; and a polyphase static inverter having its input terminals connected to said rectifier and its output terminals connected to said transmission line and said first machine stator winding.
Claim 4
Dependent Claim
35 words
The apparatus of claim 2 wherein said frequency changer further comprises: a source of DC voltage connected to the input terminals of said inverter for supplying starting excitation to said first machine via said inverter.
Claim 5
Dependent Claim
16 words
The apparatus of claim 2 further comprising: switch means for disconnecting said rectifier from said inverter.
Claim 6
Dependent Claim
16 words
The apparatus of claiM 3 further comprising: switch means for disconnecting said rectifier from said inverter.
Claim 7
Dependent Claim
96 words
A process for the generation of constant-frequency power with a variable-speed prime mover comprising the steps of: mounting first and second polyphase, wound-rotor induction machines on the same drive shaft; electrically connecting the rotors of the machines in reverse phase sequence; rectifying the voltage induced in the stator winding of one of the machines; inverting the rectified stator voltage to a constant frequency alternating voltage of a selected magnitude; delivering the constant frequency alternating voltage to the stator winding of the other machine; and delivering power from the stator windings of both machines to a load.
Claim 8
Dependent Claim
96 words
A process for the generation of constant-frequency power with a variable-speed prime mover comprising the steps of: mounting first and second polyphase, wound-rotor induction machines on the same drive shaft; electrically connecting the rotors of the machines in reverse phase sequence; rectifying the voltage induced in the stator winding of one of the machines; inverting the rectified stator voltage to a constant frequency alternating voltage of a selected magnitude; delivering the constant frequency alternating voltage to the stator winding of the other machine; and delivering power from the stator windings of both machines to a load.
Claim 9
Dependent Claim
24 words
The process of claim 6 comprising the further step of: supplying energization to the stator winding of the said other machine for starting purposes.
Claim 10
Dependent Claim
84 words
The process of claim 7 wherein the step of supplying starting energization comprises: electrically isolating the stator winding of said one of the machines from the stator winding of said other of the machines; inverting the output voltage of an external direct current source to provide an energizing voltage for the said other machine; and reconnecting the stator winding of said one of said machines to the system whereby the voltage induced therein will be rectified and inverted and the machines will be self-excited.
Claim 11
Dependent Claim
40 words
The process of claim 8 wherein the step of reconnecting comprises: matching the rectified stator winding induced voltage and the external source voltage prior to inverting; and delivering the rectified stator winding induced voltage for inversion to a constant-frequency voltage.
Claim 12
Dependent Claim
32 words
The process of claim 8 further comprising; supplying a direct current load from the external source and with power from the stator winding of the said one of said machines after rectification.
Claim 13
Dependent Claim
115 words
A process for providing, from a constant-frequency source of electrical energy, a variable speed mechanical output comprising: mounting first and second polyphase, wound-rotor induction machines on a common drive shaft; electrically connecting the rotors of the machines in reverse phase sequence; delivering energy at constant frequency from the source to the stator winding of the first machine whereby the first machine will operate as an induction motor; rectifying the voltage induced the the second machine stator; inverting the rectified second machine stator voltage to the energy source frequency; connecting the converted second machine stator voltage to the source; and varying the magnitude of the converted voltage whereby the rotational speed of the machines will vary.
Claim 14
Dependent Claim
115 words
A process for providing, from a constant-frequency source of electrical energy, a variable speed mechanical output comprising: mounting first and second polyphase, wound-rotor induction machines on a common drive shaft; electrically connecting the rotors of the machines in reverse phase sequence; delivering energy at constant frequency from the source to the stator winding of the first machine whereby the first machine will operate as an induction motor; rectifying the voltage induced the the second machine stator; inverting the rectified second machine stator voltage to the energy source frequency; connecting the converted second machine stator voltage to the source; and varying the magnitude of the converted voltage whereby the rotational speed of the machines will vary.
Claim 15
Dependent Claim
27 words
The process of claim 11 wherein the step of varying the magnitude of the converted second machine stator voltage comprises adjusting the rectified second machine stator voltage.
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) | 1974-03-22 | 1974-09-21 | 1975-03-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-22 | 1978-09-21 | 1979-03-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-22 | 1982-09-21 | 1983-03-23 | $7700.00 | Window Closed / Lapsed |