ELECTRONIC COMMUTATION SYSTEM FOR MOTORS
First Claim
1. An electronic motor that comprises, in combination, an armature winding having an even number of coils connected in a closed-loop configuration, an even number of switching devices connected to conduct electric current between a power source and the nodes of the armature winding, a field electromagnetically coupled to the armature, magnetic coupling means electrically connected serially through said switching devices to said coils to introduce commutation voltages through said electrical connection to the coils in the armature winding, the magnitude of commutation voltages thereby introduced being independent of motor speed, and means for initiating commutation of each coil of the winding.
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Accused Products
Abstract
An electronic motor to connect to a DC power source and to provide a variable speed or a controllable fixed speed motor. There is disclosed a novel arrangement for effecting commutation of current in the armature windings of the motor. Commutation is initiated by signals from a variable frequency generator or from a position sensor. In either case, in the described embodiment, commutation is effected by silicon-controlled rectifiers, diodes, a transformer and drive circuitry therefor, the rectifiers being connected serially in pairs to the motor armature such that current is introduced to the armature winding through a rectifier of one pair and removed therefrom through a rectifier of another pair, the two current-carrying rectifiers changing with each commutation and the transformer being in part connected to the rectifiers such that during commutation a commutating voltage from the transformer is introduced through four rectifiers to the two armature coils undergoing commutation.
18 Citations
16 Claims
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1. An electronic motor that comprises, in combination, an armature winding having an even number of coils connected in a closed-loop configuration, an even number of switching devices connected to conduct electric current between a power source and the nodes of the armature winding, a field electromagnetically coupled to the armature, magnetic coupling means electrically connected serially through said switching devices to said coils to introduce commutation voltages through said electrical connection to the coils in the armature winding, the magnitude of commutation voltages thereby introduced being independent of motor speed, and means for initiating commutation of each coil of the winding.
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2. An electronic motor as claimed in claim 1 in which the switching devices are diodes used in conjunction with a mechanical commutator.
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3. An electronic motor as claimed in claim 1 in which the switching devices are semiconductor controlled rectifier switches which are activated by signals derived from a position sensor for detecting relative orientation between the magnetic fluxes of the field and the armature.
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4. Apparatus as claimed in claim 1 in which the position sensor comprises a circuit including a differential comparator connected to change state when the voltage of the coil to-be-commutated is equal to the instantaneous value of a reference signal.
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5. Apparatus as claimed in claim 4 in which the differential comparator is connected to receive said reference signal from the coil commutated immediately preceding said coil to-be-commutated.
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6. Apparatus as claimed in claim 1 having starting means which includes:
- means for rendering the position sensor ineffective, a variable frequency AC source connected to initate commutations in lieu of the ineffective position sensor, and means for rendering the position sensor effective to initiate said commutations and the variable frequency source ineffective for such purpose.
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7. An electronic motor as claimed in claim 1 in which the field excitation is produced by induction action from the armature.
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8. An electronic motor that comprises, in combination, an armature winding having an even number of coils connected in a closed-loop configuration, an even number of switching devices connected to conduct electric current between a power source and the armature winding, a field electromagnetically coupled to the armature, position sensor means for detecting relative orientation between the magnetic fluxes of the field and the armature, a transformer serially connected through the switching devices to introduce commutation voltages through said switching devices to the coils of the armature winding, the position sensor means being connected to initiate commutation of each winding, and a plurality of diodes connected between the transformer and the power source.
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9. In an electronic motor an armature having an armature winding that contains an even number of coils connected in a closed-loop configuration, an even number of switching devices connected to conduct electric current between a power source and nodes of the armature winding, a field electromagnetically coupled to the armature, transformer means directly electrically connected to introduce commutation voltages serially through said switching devices to the coils of the armature winding, and means for initiating commutation of each coil.
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10. An electronic motor as claimed in claim 9, in which the switching devices are SCR'"'"''"'"'s and in which the means for initiating commutation includes a position sensor, said position sensor being adapted in the running mode commutation of each coil of said armature winding to initiate such commutation.
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11. An electronic motor as claimed in claim 9, in which the means for initiating commutation includes a variable frequency oscillator to initiAte commutation.
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12. An electronic motor as claimed in claim 9 which includes a commutation pulse generator connected to the transformer means, which commutation pulse generator generates a square pulse voltage of alternating polarity to force commutation of armature current.
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13. An electronic motor as claimed in claim 12 in which the transformer means comprises a transformer having a primary and two secondaries, the pulse generator being connected across the primary and the secondaries being connected to coils 180 electrical degrees apart in said armature winding, said square pulse voltage introduced to the primary appearing as an output voltage from said secondaries, each secondary being connected to introduce a voltage to the associated coil which opposes the voltage in said associated coil during commutation and reduces current flow in said associated coil to zero in the course of such commutation.
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14. An electronic motor as claimed in claim 13 in which said switching devices are SCR'"'"''"'"'s and which includes control means applied across the gate and cathode of each SCR, the control means being adapted to bias a particular SCR ON, said particular SCR being turned OFF when the opposing voltage from the transformer tries to make the current flow backward in said particular SCR, said control means being adapted simultaneously to turn another SCR ON, thereby causing the current in the said associated coil to reverse direction.
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15. An electronic motor as claimed in claim 13 in which a plurality of diodes is connected across the primary of the transformer to provide a short circuiting path for current inducted in said primary to allow the transformer to reset.
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16. An electronic motor as claimed in claim 15 which includes a plurality of diodes connected in the output circuit of the secondaries of the transformer to isolate electrical connections between the secondaries and one associated SCR from the connections between the secondaries and another associated SCR.
Specification