Three-phase motor control
OwnerOtto J. M. Smithinventor
Life of this patent
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Abstract
A three-phase induction motor is driven efficiently from a single-phase power supply by reconnecting the motor windings and using two or more capacitors to provide balanced currents and voltages in the windings at preselected values of power. A similar method is used to drive a three-terminal conventional motor from a single-phase supply by using a tapped autotransformer with two different voltages and two different capacitors to excite the third motor terminal. Capacitor switching in all embodiments is controlled by feedback from the voltage across the winding with capacitor excitation.
Claims69
A squirrel-cage induction motor having four motor terminals with a first winding connected between a first motor terminal and a second motor terminal, a second winding connected between said second motor terminal and a third motor terminal, a third winding connected between said third motor terminal and a fourth motor terminal, a two-wire single-phase power supply, a first wire of the said power supply connected to said first motor terminal, the second wire of the said power supply connected to said third motor terminal, a first capacitor connected between said first motor terminal and said fourth motor terminal, and means for connecting a second capacitor between said second motor terminal and said third motor terminal.
A three-winding three-phase motor, each winding having first and second winding terminals so polarized that a rotating flux in the motor air-gap will generate a first alternating voltage difference in the first winding from its first terminal to its second terminal which leads in phase by 120 electrical degrees a second generated alternating voltage difference in the second winding from its first terminal to its second terminal, and said second alternating voltage leads in phase by 120 electrical degrees a third generated alternating voltage difference in the third winding from its first terminal to its second terminal, a two-wire single-phase supply, a first wire of said supply connected to the first terminal of the first winding, the second wire of said supply connected to the first terminal of the second winding and also to the first terminal of the third winding, the second terminal of the first winding connected to the second terminal of the third winding, and a first capacitor connected between the second terminal of the second winding and the first wire of the said supply.
The method of exciting a three-winding three-phase motor, each winding having first and second winding terminals so polarized that a rotating flux in the motor air-gap will generate a first alternating voltage difference in the first winding from its first terminal to its second terminal which leads in phase by 120 electrical degrees a second generated alternating voltage difference in the second winding from its first terminal to its second terminal, and said second alternating voltage leads in phase by 120 electrical degrees a third generated alternating voltage difference in the third winding from its first terminal to its second terminal, a two-wire single-phase supply, a first wire of said supply connected to the first terminal of the first winding, the second wire of said supply connected to the first terminal of the second winding and also to the first terminal of the third winding, the second terminal of the first winding connected to the second terminal of the third winding, and a first capacitor connected between the second terminal of the second winding and the first wire of the said supply.
A squirrel-cage induction motor containing a rotating magnetic field, said motor having four terminals with a first winding connected between a first motor terminal and a second motor terminal, the internal magnetic polarity of said first winding from said first terminal to said second terminal with respect to said magnetic field having a first phase, a second winding connected between said second motor terminal and a third motor terminal, a second internal phase of said second winding from said second terminal to said third terminal with respect to said magnetic field, said second phase having a phase magnitude with respect to said first phase nominally lagging 60 degrees, and in operation more than 30 degrees and less than 90 degrees, a third winding connected between said third motor terminal and a fourth motor terminal, a third internal phase of said third winding from said third terminal to said fourth terminal with respect to said magnetic field, said third phase having a phase magnitude with respect to said second phase nominally lagging 60 degrees and in operation more than 30 degrees and less than 90 degrees, a two-wire single-phase power supply, a first wire of said power supply connected to said first motor terminal, the second wire of said power supply connected to said third motor terminal, a first capacitor connected between said first motor terminal and said fourth motor terminal, and means for connecting a second capacitor between said second motor terminal and said third motor terminal.
A three-phase induction motor with a first motor winding connected between a first terminal and a fourth terminal, a second motor winding connected between a second terminal and a fifth terminal, a third motor winding connected between a third terminal and a sixth terminal, said windings polarized such that if said terminals four, five, and six were connected together then said terminals one, two and three would comprise a wye-connected three-phase motor, an electrical connection of said fourth terminal to said fifth terminal, an electrical connection of said first terminal to said third terminal, a two-wire single-phase power supply, a first wire of the said power supply connected to said first terminal, the second wire of said power supply connected to said second terminal, and means for connecting a first capacitor between said second motor terminal and said sixth motor terminal.
A motor as in claim 43, including a second capacitor connected between said second terminal and said fifth terminal.
A three-phase induction motor with a first motor winding having a designated first terminal and a fourth terminal, a second motor winding having a designated second terminal and a fifth terminal, a third motor winding having a designated third terminal and a sixth terminal, said windings polarized such that if said terminals four, five, and six were connected together then said terminals one, two and three would comprise a wye-connected three-phase motor, an electrical connection of said fourth terminal to said fifth terminal, an electrical connection of said second terminal to said third terminal, a two-wire single-phase power supply, a first wire of the said power supply connected to said first terminal, the second wire of said power supply connected to said second terminal, and means for connecting a first capacitor between said first terminal and said sixth terminal.
A three-phase induction motor with a first winding connected between a first terminal and a fourth terminal, a second winding connected between a second terminal and a fifth terminal, a third winding connected between a third terminal and a sixth terminal, said windings polarized such that if said terminals four, five, and six were connected together then said terminals one, two and three would comprise a wye-connected three-phase motor, an electrical connection of said fourth terminal to said fifth terminal, an electrical connection of said first terminal to said third terminal, a two-wire single-phase power supply, a first wire of the said power supply connected to said first terminal, the second wire of said power supply connected to said second terminal, and means for connecting a first capacitor between said second terminal and said sixth terminal.
A three-phase induction motor with a first winding connected between a first terminal and a fourth terminal, a second motor winding connected between a second terminal and a fifth terminal, a third motor winding connected between a third terminal and a sixth terminal, said windings polarized such that if said terminals one and five were connected together, and if terminals three and four were connected together, and if terminals two and six were connected together, then terminals one, two and three would comprise a delta-connected three-phase motor, an electrical connection of said fourth terminal to said fifth terminal, an electrical connection of said first terminal to said third terminal, a two-wire single-phase power supply, a first wire of the said power supply connected to said first terminal, the second wire of said power supply connected to said second terminal, and means for connecting a first capacitor between said second terminal and said sixth terminal.
A three-phase induction motor with a first winding connected between a first terminal and a fourth terminal, a second motor winding connected between a second terminal and a fifth terminal, a third motor winding connected between a third terminal and a sixth terminal, said windings polarized such that if said terminals one and six were connected together, and if terminals two and four were connected together, and if terminals three and five were connected together then said terminals one, two and three would comprise a delta-connected three-phase motor, an electrical connection of said fourth terminal to said fifth terminal, an electrical connection of said first terminal to said third terminal, a two-wire single-phase power supply, a first wire of the said power supply connected to said first terminal, the second wire of said power supply connected to said second terminal, and means for connecting a first capacitor between said second terminal and said sixth terminal.
A squirrel-cage induction motor having four motor terminals with a first winding connected between a first motor terminal and a second motor terminal, a second winding connected between said second motor terminal and a third motor terminal, a third winding connected between said third motor terminal and a fourth motor terminal, a two-wire single-phase power supply, a first wire of said power supply connected to said first motor terminal, the second wire of said power supply connected to said third motor terminal, the voltage between said first motor terminal and said second motor terminal being a first voltage, the voltage between said second motor terminal and said third motor terminal being a second voltage, the voltage between said third motor terminal and said fourth motor terminal being a third voltage, the voltage between said first motor terminal and said fourth motor terminal being a fourth voltage, the magnitude of said fourth voltage being more than ten percent more than the magnitude of said second voltage, and a capacitor connected between said first motor terminal and said fourth motor terminal.
A squirrel-cage induction motor having four motor terminals with a first winding connected between a first motor terminal and a second motor terminal, a second winding connected between said second motor terminal and a third motor terminal, a third winding connected between said third motor terminal and a fourth motor terminal, a two-wire single-phase power supply, a first wire of said power supply connected to said first motor terminal, the second wire of said power supply connected to said third motor terminal, the voltage between said first motor terminal and said second motor terminal being a first voltage, the voltage between said second motor terminal and said third motor terminal being a second voltage, the voltage between said third motor terminal and said fourth motor terminal being a third voltage, the voltage between said first motor terminal and said fourth motor terminal being a fourth voltage, the magnitude of said fourth voltage being more than ten percent more than the magnitude of said third voltage, and a capacitor connected between said first motor terminal and said fourth motor terminal.
The method of using a two-wire single-phase supply to excite a three-winding three-phase motor, each winding having first and second terminals with a common reference polarity across said first and second terminals wherein a first terminal of the first one of the said windings is connected to the first wire of the said single-phase supply, and wherein a first terminal of the second one of said windings is connected to the second wire of the said supply, and wherein the second terminal of the said first winding is connected to the second terminal of the said first winding, and wherein the first terminal of the third said winding is also connected to the said second wire, and wherein the second terminal of the said third winding is excited by a composite current generated by the sum of two different alternating currents with different phase angles.
A three-phase motor with three terminals and a single-phase power supply with two lines, wherein the first line of the said power supply is connected to the first terminal of the said motor, the second line of the said power supply is connected to the second terminal of the said motor, an autotransformer with four taps, the first tap connected to the said first terminal, the second tap connected to the said second terminal, a first series circuit of a first capacitor and a first switch connected between the third tap of the said autotransformer and the third terminal of the said motor, and a second series circuit of a second capacitor and a second switch connected between the fourth tap of the said autotransformer and the third terminal of the said motor.
A squirrel-cage electrical induction machine having four machine terminals with a first winding connected between a first machine terminal and a second machine terminal, a second winding connected between said second machine terminal and a third machine terminal, a third winding connected between said third machine terminal and a fourth machine terminal, a two-wire single-phase power system, a first wire of the said power system connected to said first machine terminal, the second wire of the said power system connected to said third machine terminal, and means for connecting a capacitor between said first machine terminal and said fourth machine terminal.
Dependencies are inferred from the claim text.