Motor starting circuit with time delay cut-out and restart

A motor starting circuit for a single phase AC motor having a main winding and start winding energizeable by an AC source, comprising:

• a start winding circuit including said start winding and having a first main terminal connected to said AC source and having a second main terminal;
• start switch means connected in series with said start winding circuit, said start switch means having a first main terminal connected to said second main terminal of said start winding circuit and having a second main terminal connected to said AC source, such that the series connected start switch means and start winding circuit are connected across said AC source, said start switch means having a conductive ON state conducting current therethrough to complete a current path through said start winding circuit from said AC source, said start switch means having a nonconductive OFF state blocking current flow through said start winding circuit from said AC source, said start switch means having a gate terminal for controlling conduction of said start switch means, and comprising resistance means connected between said gate terminal and said second main terminal of said start switch means;
• turn-on switch means connected across said start switch means and not across said start winding circuit, said turn-on switch means having a first main terminal connected to said first main terminal of said start switch means and having a second main terminal connected to the junction of said gate terminal of said start switch means and said resistance means, said turn-on switch means having a conductive ON state conducting current therethrough to complete a current path from said AC source through said start winding circuit through said turn-on switch means to said gate terminal of said start switch means to turn the latter ON, said turn-on switch means having a nonconductive OFF state blocking current flow to said gate terminal of said start switch means such that the latter is OFF, said turn-on switch means having a gate terminal for controlling conduction of said turn-on switch means, and comprising second resistance means connected between said first main terminal of said turn-on switch means and said gate terminal of said turn-on switch means to supply gate current from said AC source through said start winding circuit through said second resistance means to said gate terminal of said turn-on switch means to turn the latter ON, and comprising third resistance means connected between said gate terminal of said turn-on switch means and said second main terminal of said turn-on switch means;
• cut-out switch means connected across said third resistance means, said cut-out switch means having a first main terminal connected to the junction of said gate terminal of said turn-on switch means and said second resistance means, said cut-out switch means having a second main terminal connected to the junction of said second main terminal of said turn-on switch means and said third resistance means, said cut-out switch means having a conductive ON state conducting current therethrough to divert gate current through said second resistance means away from said gate of said turn-on switch means such that the latter is OFF, said cut-out switch means having a nonconductive OFF state blocking current flow therethrough such that gate current through said second resistance means flows to said gate terminal of said turn-on switch means to turn the latter ON;
• a timing circuit connected across said AC source and across the series connected start winding circuit and start switch means, said timing circuit including a timing capacitor controlling conduction of said cut-out switch means such that when said timing capacitor is charged to a given threshold voltage after a given timing interval the charge on said capacitor turns ON said cut-out switch means,
• wherein said cut-out switch means comprises a two terminal diac, the first terminal of said diac being connected to said junction of said gate terminal of said cut-out switch means and said second resistance means, the second terminal of said diac being connected to said junction of said second main terminal of said turn-on switch means and said third resistance means, and wherein said timing capacitor is connected in parallel across said diac, said timing capacitor having one plate connected to said first diac terminal and having a second plate connected to said second diac terminal.

A motor starting circuit for a single phase AC motor having a main winding and start winding energizeable by an AC source, comprising:

• a start winding circuit including said start winding and having a first main terminal connected to said AC source and having a second main terminal;
• start switch means connected in series with said start winding circuit, said start switch means having a first main terminal connected to said second main terminal of said start winding circuit and having a second main terminal connected to said AC source, such that the series connected start switch means and start winding circuit are connected across said AC source, said start switch means having a conductive ON state conducting current therethrough to complete a current path through said start winding circuit from said AC source, said start switch means having a nonconductive OFF state blocking current flow through said start winding circuit from said AC source, said start switch means having a gate terminal for controlling conduction of said start switch means, and comprising resistance means connected between said gate terminal and said second main terminal of said start switch means;
• turn-on switch means connected across said start switch means and not across said start winding circuit, said turn-on switch means having a first main terminal connected to said first main terminal of said start switch means and having a second main terminal connected to the junction of said gate terminal of said start switch means and said resistance means, said turn-on switch means having a conductive ON state conducting current therethrough to complete a current path from said AC source through said start winding circuit through said turn-on switch means to said gate terminal of said start switch means to turn the latter ON, said turn-on switch means having a nonconductive OFF state blocking current flow to said gate terminal of said start switch means such that the latter is OFF, said turn-on switch means having a gate terminal for controlling conduction of said turn-on switch means, and comprising second resistance means connected between said first main terminal of said turn-on switch means and said gate terminal of said turn-on switch means to supply gate current from said AC source through said start winding circuit through said second resistance means to said gate terminal of said turn-on switch means to turn the latter ON, and comprising third resistance means connected between said gate terminal of said turn-on switch means and said second main terminal of said turn-on switch means;
• cut-out switch means connected across said third resistance means, said cut-out switch means having a first main terminal connected to the junction of said gate terminal of said turn-on switch means and said second resistance means, said cut-out switch means having a second main terminal connected to the junction of said second main terminal of said turn-on switch means and said third resistance means, said cut-out switch means having a conductive ON state conducting current therethrough to divert gate current through said second resistance means away from said gate of said turn-on switch means such that the latter is OFF, said cut-out switch means having a nonconductive OFF state blocking current flow therethrough such that gate current through said second resistance means flows to said gate terminal of said turn-on switch means to turn the latter ON;
• a timing circuit connected across said AC source and across the series connected start winding circuit and start switch means, said timing circuit including a timing capacitor controlling conduction of said cut-out switch means such that when said timing capacitor is charged to a given threshold voltage after a given timing interval the charge on said capacitor turns ON said cut-out switch means;
• restart switch means connected in series with said timing circuit for controlling charging of said timing capacitor, said restart switch means having a first main terminal connected to the junction of said AC source and said first main terminal of said start winding circuit and having a second main terminal connected to said timing circuit, said restart switch means having a conductive ON state conducting current therethrough to complete a current path from said AC source through said restart switch means to charge said timing capacitor, said restart switch means having a nonconductive OFF state blocking current flow to prevent charging of said timing capacitor, said restart switch means having a gate circuit connected across said start winding, such that when said start switch means turns ON, current flows through said start winding and said gate circuit of said restart switch means and turns ON said restart switch means, and such that upon time delay turn OFF of said start switch means the induced voltage in said start winding due to motor rotation is normally sufficient to provide sufficient gate drive bias in said gate circuit of said restart switch means to turn the latter ON, and such that upon decrease in motor speed below a given value, the induced voltage in said start winding is insufficient to provide enough gate drive bias for said restart switch means such that the later turns OFF, and said timing capacitor discharges such that said cut-out switch means turns OFF such that said turn-on switch means turns ON such that said start switch means turns ON and conducts current through said start winding circuit from said AC source.