Starting winding switching circuit for single-phase induction motors
First Claim
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1. A switching device for use with a single phase induction motor having a main winding, and a starting winding in series with a starting capacitor, connected in parallel across first and second supply terminals, said switching device comprising:
- a triac having first, second and gate terminals, said triac'"'"'s first terminal connected to one terminal of the the starting winding, and said triac'"'"'s second terminal connected to the second supply terminal;
a diode bridge having first and second a.c. terminals and first and second d.c. terminals, said first d.c. terminal outputting a reference potential and said second d.c. terminal outputting a positive rectified potential, said second a.c. terminal connected to said triac'"'"'s gate terminal;
a first resistor connected between said triac'"'"'s first terminal and said diode bridge'"'"'s first a.c. terminal;
a second resistor connected between said triac'"'"'s second terminal and said triac'"'"'s gate terminal;
a silicon control rectifier (SCR) having anode, cathode and gate terminals, said SCR'"'"'s anode terminal connected to said diode bridge'"'"'s second d.c. terminal, and said SCR'"'"'s cathode terminal connected to said diode bridge'"'"'s first d.c. terminal;
a third resistor connected between said diode bridge'"'"'s first a.c. terminal and said SCR'"'"'s anode terminal;
a fourth resistor connected between said SCR'"'"'s anode terminal and said SCR'"'"'s gate terminal;
a PNP transistor having emitter, collector and base terminals, said PNP transistor'"'"'s emitter terminal connected to said SCR'"'"'s gate terminal, and said PNP transistors collector terminal connected to said SCR'"'"'s cathode terminal;
an NPN transistor having emitter, collector and base terminals, said NPN transistor'"'"'s collector terminal connected to said PNP transistor'"'"'s base terminal;
a first capacitor connected between said NPN transistor'"'"'s collector terminal and said NPN transistor'"'"'s base terminal;
a fifth resistor connected between said NPN transistor'"'"'s base terminal and said NPN transistor'"'"'s emitter terminal;
a diode having anode and cathode terminals;
a sixth resistor connected between said NPN transistor'"'"'s emitter terminal and said diode'"'"'s anode terminal;
a second capacitor connected between said PNP transistor'"'"'s emitter terminal and said diode'"'"'s anode terminal;
a seventh resistor connected between said PNP transistor'"'"'s emitter terminal and said diode'"'"'s cathode terminal; and
an eighth resistor connected between said diode'"'"'s cathode terminal and the other terminal of the starting winding.
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Abstract
The switching device of the present invention electrically connects a single-phase induction motor'"'"'s starting winding to the motor'"'"'s circuitry upon start-up, and disconnects it once the motor reaches a first predetermined speed. If the motor'"'"'s speed drops below a second predetermined speed, the switching device reconnects the starting winding to the motor'"'"'s circuitry until the motor again reaches the first predetermined speed. At start-up, diode bridge D1 turns ON, turning ON SCR S2. With the SCR ON, the diode bridge is short-circuited, drawing a large current through the bridge'"'"'s a.c. side. This current flows through resistor R8, and the voltage drop across R8 is large enough to turn triac S1 ON. Thus, current flows through starting coil L2. When the motor reaches a first predetermined speed, the voltage across the starting coil is large enough to turn NPN transistor TR2 ON, turning PNP transistor TR1 ON. Accordingly, the SCR turns OFF, eliminating the large current drawn through the a.c. side of the diode bridge, and the triac turns OFF. If the motor speed dips below a second predetermined value, lower than the first, transistor TR1 is cutoff, and the triac subsequently turns back ON until the first predetermined speed is reached.
82 Citations
2 Claims
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1. A switching device for use with a single phase induction motor having a main winding, and a starting winding in series with a starting capacitor, connected in parallel across first and second supply terminals, said switching device comprising:
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a triac having first, second and gate terminals, said triac'"'"'s first terminal connected to one terminal of the the starting winding, and said triac'"'"'s second terminal connected to the second supply terminal; a diode bridge having first and second a.c. terminals and first and second d.c. terminals, said first d.c. terminal outputting a reference potential and said second d.c. terminal outputting a positive rectified potential, said second a.c. terminal connected to said triac'"'"'s gate terminal; a first resistor connected between said triac'"'"'s first terminal and said diode bridge'"'"'s first a.c. terminal; a second resistor connected between said triac'"'"'s second terminal and said triac'"'"'s gate terminal; a silicon control rectifier (SCR) having anode, cathode and gate terminals, said SCR'"'"'s anode terminal connected to said diode bridge'"'"'s second d.c. terminal, and said SCR'"'"'s cathode terminal connected to said diode bridge'"'"'s first d.c. terminal; a third resistor connected between said diode bridge'"'"'s first a.c. terminal and said SCR'"'"'s anode terminal; a fourth resistor connected between said SCR'"'"'s anode terminal and said SCR'"'"'s gate terminal; a PNP transistor having emitter, collector and base terminals, said PNP transistor'"'"'s emitter terminal connected to said SCR'"'"'s gate terminal, and said PNP transistors collector terminal connected to said SCR'"'"'s cathode terminal; an NPN transistor having emitter, collector and base terminals, said NPN transistor'"'"'s collector terminal connected to said PNP transistor'"'"'s base terminal; a first capacitor connected between said NPN transistor'"'"'s collector terminal and said NPN transistor'"'"'s base terminal; a fifth resistor connected between said NPN transistor'"'"'s base terminal and said NPN transistor'"'"'s emitter terminal; a diode having anode and cathode terminals; a sixth resistor connected between said NPN transistor'"'"'s emitter terminal and said diode'"'"'s anode terminal; a second capacitor connected between said PNP transistor'"'"'s emitter terminal and said diode'"'"'s anode terminal; a seventh resistor connected between said PNP transistor'"'"'s emitter terminal and said diode'"'"'s cathode terminal; and an eighth resistor connected between said diode'"'"'s cathode terminal and the other terminal of the starting winding.
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2. A switching device for use with a single phase induction motor having a main winding, and a starting winding in series with a starting capacitor, connected in parallel across first and second supply terminals, said switching device comprising:
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a triac having first, second and gate terminals, said triac'"'"'s first terminal connected to one terminal of the the starting winding, and said triac'"'"'s second terminal connected to the second supply terminal; a diode bridge having first and second a.c. terminals and first and second d.c. terminals, said first d.c. terminal outputting a reference potential and said second d.c. terminal outputting a positive rectified potential, said second a.c. terminal connected to said triac'"'"'s gate terminal; a first resistor connected between said triac'"'"'s first terminal and said diode bridge'"'"'s first a.c. terminal; a second resistor connected between said triac'"'"'s second terminal and said triac'"'"'s gate terminal; a silicon control rectifier (SCR) having anode, cathode and gate terminals, said SCR'"'"'s anode terminal connected to said diode bridge'"'"'s second d.c. terminal, and said SCR'"'"'s cathode terminal connected to said diode bridge'"'"'s first d.c. terminal; a third resistor connected between said SCR'"'"'s anode terminal and said SCR'"'"'s gate terminal; a first NPN transistor having emitter, collector and base terminals, said first NPN transistor'"'"'s collector terminal connected to said SCR'"'"'s gate terminal, and said first NPN transistor'"'"'s emiter terminal connected to said SCR'"'"'s cathode terminal; a second NPN transistor having emitter, collector and base terminals, said second NPN transistor'"'"'s emitter terminal connected to said first NPN transistor'"'"'s base terminal; a first capacitor connected between said second NPN transistor'"'"'s collector terminal and said second NPN transistor'"'"'s base terminal; a fourth resistor connected between said second NPN transistor'"'"'s base terminal and said first NPN transistor'"'"'s emitter terminal; a diode having anode and cathode terminals; a fifth resistor connected between said second NPN transistor'"'"'s collector terminal and said diode'"'"'s cathode terminal; a second capacitor connected between said first NPN transistor'"'"'s emitter terminal and said diode'"'"'s cathode terminal; a sixth resistor connected between said first NPN transistor'"'"'s emitter terminal and said diode'"'"'s anode terminal; and a seventh resistor connected between said diode'"'"'s anode terminal and the other terminal of the starting winding.
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Specification
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Current AssigneeIn S. Kim
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Original AssigneeIn S. Kim
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InventorsKim, In S.
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Primary Examiner(s)Smith, Jr., David
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Application NumberUS06/657,361Time in Patent Office907 DaysField of Search318/786, 318/785, 318/789US Class Current318/786CPC Class CodesH02P 1/44 by phase-splitting with a c...
