Method and apparatus for starting capacitive start, induction run and capacitive start, capacitive run electric motors
First Claim
1. A system for starting one of a capacitor start induction run and capacitor start-capacitor run motor having a main winding and an auxiliary winding comprising:
- a triac having a gate and having first and second main terminals connected in series with the auxiliary winding to control the energization thereof,control apparatus comprising;
a power supply means for providing first DC control circuit supply and second line voltage reference voltages,bias OK means to compare supply voltage to the first reference voltage, a first condition being satisfied when the supply voltage exceeds the first reference voltage,line OK means to compare line voltage to the second reference voltage, a second condition being satisfied when the line voltage exceeds the second reference voltage,cut-in voltage means to compare start winding voltage to a selected cut-in level, a third condition being satisfied when the start winding voltage is less then the cut-in level,zero crossing detection means to detect the crossing through zero of a sinusoidal voltage across the triac and, with the other three conditions being satisfied, to generate an enable signal when the sinusoidal voltage has cross zero and is below a selected maximum; and
,means to turn on the triac in response to the enable signal.
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Accused Products
Abstract
A solid state starting system for electric motors having main and auxiliary windings of the capacitor start induction run and capacitor start-capacitor run types uses a triac serially connected to the auxiliary winding. The system differentially measures the auxiliary winding voltage and provides a triac gate signal when in the START mode. When the auxiliary voltage reaches a calibratable cut-out voltage the triac is disabled until the auxiliary winding voltage decreases to a level below a calibratable cut-in voltage. The slope of the percent motor speed cut-out versus percent line voltage is calibratable to permit compensation for variations in line voltage. The triac can be directly driven or driven through an optically coupled interface having a triac output (OCI).
82 Citations
15 Claims
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1. A system for starting one of a capacitor start induction run and capacitor start-capacitor run motor having a main winding and an auxiliary winding comprising:
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a triac having a gate and having first and second main terminals connected in series with the auxiliary winding to control the energization thereof, control apparatus comprising; a power supply means for providing first DC control circuit supply and second line voltage reference voltages, bias OK means to compare supply voltage to the first reference voltage, a first condition being satisfied when the supply voltage exceeds the first reference voltage, line OK means to compare line voltage to the second reference voltage, a second condition being satisfied when the line voltage exceeds the second reference voltage, cut-in voltage means to compare start winding voltage to a selected cut-in level, a third condition being satisfied when the start winding voltage is less then the cut-in level, zero crossing detection means to detect the crossing through zero of a sinusoidal voltage across the triac and, with the other three conditions being satisfied, to generate an enable signal when the sinusoidal voltage has cross zero and is below a selected maximum; and
,means to turn on the triac in response to the enable signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for starting one of a capacitor start induction run and capacitor start-capacitor run motors having a main winding and an auxiliary winding with a triac serially connected to the auxiliary winding to control the energization thereof, comprising the steps of:
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differentially measuring the start winding voltage, determining the resultant difference voltage between the lines and start winding voltages, applying the resultant voltage to a cut-out comparator means, and to a cut-in comparator means, generating a first current through a first resistor, generating a second current through a second resistor, combining the first current and the second IDC current, generating a third current through a third resistor proportional to 1/2 of the first plus the second currents, generating a fourth current through a fourth resistor proportional to 1/2 of the first plus the second current, generating a cut-out voltage through the third resistor and the third current and applying it to the cut-out comparator means, generating a cut-in voltage through the fourth resistor and the fourth current and applying it to the cut-in comparator means, coupling the output of the cut-out and cut-in comparator to mode logic means; and producing a signal to turn on the triac in response to the output of the logic means. - View Dependent Claims (10, 11, 12)
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- 13. A method for starting an electric motor having a main winding and an auxiliary winding with a gated solid state switch connected to the auxiliary winding to control the energization thereof comprising the steps of generating signals proportional to a line and start winding voltages, applying gate current to the gated solid state switch when energizing the motor, providing a selected slope of line voltage versus cut-out voltage and interrupting the gate current when the start winding voltage has reached a selected cut-out value relative to line voltage.
Specification