Method and apparatus for starting capacitive start, induction run and capacitive start, capacitive run electric motors

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:

• 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.