US3714532A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Brushless direct current motor including resonant circuits and differential amplifier for controlling commutation
Assignee: Globe Motors Inc
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Filing: 1970-11-06
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Granted: 1973-01-30
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Expires: 1990-11-06
Abstract
Abstract In a brushless direct current motor, the commutation of current through the motor field windings is controlled by the voltage level across a plurality of sensing inductors mounted to detect the position of a metallic segment which rotates with the motor armature. The sensing inductors are supplied with a high frequency current from a fixed frequency oscillator, and changes in the resonance frequency of the inductors due to the proximity of the metallic segment causes the voltage across the inductors to change sharply. The voltage outputs from complementary inductors are applied to a differential amplifier, and a change in voltage is sensed to control the current through the field windings. By comparing the outputs from complementary pairs of inductors simultaneously, the output from the differential amplifier is made substantially independent of the frequency and magnitude of the high frequency excitation current. Also, the sensing inductors are kept small and complementary coils are matched to minimize angular errors.
Inventors
- 👤 Curry M Mc
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 03:36
CPC Classifications
H; H02; H02K; H02K29/00; H02K29/06; H02K29/12
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
218 words
In a brushless direct current motor including a permanent magnet rotor, angularly spaced field windings surrounding said rotor, position indicating means mounted to rotate with said rotor, at least a pair of inductors mounted to sense the angular position of said position indicating means, and circuit means responsive to said sensing inductors for controlling the current flow through said field windings in such a way to cause said rotor to rotate, the improvement comprising a continuously running oscillator for supplying fixed high frequency energy to said sensing inductors, means associated with each inductor to form a resonant circuit tuned to resonate at the frequency of said oscillator, said resonant circuits being alternately tuned and detuned by the rotation of said position indicating means, means for sensing the voltage across one of the reactive elements of said resonant circuits to produce an output for controlling the current through said field winding at specified angular positions of said rotor to cause torque and produce rotation, said sensing means including a differential amplifier comparing the difference in the voltage developed across a complementary pair of said resonant circuits, said amplifier providing a change in output when the difference across said resonant circuits crosses through zero potential thereby to control the current through said field windings at angular positions of said rotor.
Claim 2
Dependent Claim
218 words
In a brushless direct current motor including a permanent magnet rotor, angularly spaced field windings surrounding said rotor, position indicating means mounted to rotate with said rotor, at least a pair of inductors mounted to sense the angular position of said position indicating means, and circuit means responsive to said sensing inductors for controlling the current flow through said field windings in such a way to cause said rotor to rotate, the improvement comprising a continuously running oscillator for supplying fixed high frequency energy to said sensing inductors, means associated with each inductor to form a resonant circuit tuned to resonate at the frequency of said oscillator, said resonant circuits being alternately tuned and detuned by the rotation of said position indicating means, means for sensing the voltage across one of the reactive elements of said resonant circuits to produce an output for controlling the current through said field winding at specified angular positions of said rotor to cause torque and produce rotation, said sensing means including a differential amplifier comparing the difference in the voltage developed across a complementary pair of said resonant circuits, said amplifier providing a change in output when the difference across said resonant circuits crosses through zero potential thereby to control the current through said field windings at angular positions of said rotor.
Claim 3
Dependent Claim
218 words
In a brushless direct current motor including a permanent magnet rotor, angularly spaced field windings surrounding said rotor, position indicating means mounted to rotate with said rotor, at least a pair of inductors mounted to sense the angular position of said position indicating means, and circuit means responsive to said sensing inductors for controlling the current flow through said field windings in such a way to cause said rotor to rotate, the improvement comprising a continuously running oscillator for supplying fixed high frequency energy to said sensing inductors, means associated with each inductor to form a resonant circuit tuned to resonate at the frequency of said oscillator, said resonant circuits being alternately tuned and detuned by the rotation of said position indicating means, means for sensing the voltage across one of the reactive elements of said resonant circuits to produce an output for controlling the current through said field winding at specified angular positions of said rotor to cause torque and produce rotation, said sensing means including a differential amplifier comparing the difference in the voltage developed across a complementary pair of said resonant circuits, said amplifier providing a change in output when the difference across said resonant circuits crosses through zero potential thereby to control the current through said field windings at angular positions of said rotor.
Claim 4
Dependent Claim
218 words
In a brushless direct current motor including a permanent magnet rotor, angularly spaced field windings surrounding said rotor, position indicating means mounted to rotate with said rotor, at least a pair of inductors mounted to sense the angular position of said position indicating means, and circuit means responsive to said sensing inductors for controlling the current flow through said field windings in such a way to cause said rotor to rotate, the improvement comprising a continuously running oscillator for supplying fixed high frequency energy to said sensing inductors, means associated with each inductor to form a resonant circuit tuned to resonate at the frequency of said oscillator, said resonant circuits being alternately tuned and detuned by the rotation of said position indicating means, means for sensing the voltage across one of the reactive elements of said resonant circuits to produce an output for controlling the current through said field winding at specified angular positions of said rotor to cause torque and produce rotation, said sensing means including a differential amplifier comparing the difference in the voltage developed across a complementary pair of said resonant circuits, said amplifier providing a change in output when the difference across said resonant circuits crosses through zero potential thereby to control the current through said field windings at angular positions of said rotor.
Claim 5
Dependent Claim
40 words
The motor of claim 1 further including capacitors in parallel with each said inductor and tuned to resonate with said inductors at the frequency of said oscillator, said parallel tuned circuit detuned by the proximity of said position indicating means.
Claim 6
Dependent Claim
26 words
The motor of claim 1 further including means for rectifying the voltage developed across said inductors and wherein said differential amplifier is a direct current amplifier.
Claim 7
Dependent Claim
18 words
The motor of claim 1 wherein said complementary pair of sensing inductors is matched in size and inductance.
Claim 8
Dependent Claim
42 words
The motor of claim 1 wherein said position indicating means includes a semicircular segment which rotates with the motor shaft and wherein two pairs of 180* spaced apart sensing inductors are mounted to sense the angular position of said position indicating means.
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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) | 1976-01-30 | 1976-07-31 | 1977-01-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-30 | 1980-07-31 | 1981-01-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-30 | 1984-07-31 | 1985-01-30 | $7700.00 | Window Closed / Lapsed |