Start control arrangement for split phase induction motor

A direction control arrangement for a reversible alternating current induction motor adapted for energization by a voltage signal from an external power supply, said control arrangement comprising:

• a reversible alternating current split phase induction motor including a run winding and a start winding, said run winding being electrically connected in parallel with said start winding;
• selection means for selecting motor rotation in one direction or the other;
• phase control means electrically connected in series with said start winding operative to control the duration of the conductive portion of each half-cycle of the current in said start winding;
• control means responsive to said selection means for rendering said phase control means conductive at a first predetermined phase angle when said one direction of rotation is selected thereby initiating rotation of said motor in said one direction and rendering said phase control means conductive at a second predetermined phase angle when said other direction is selected thereby initiating rotation of said motor in said opposite direction.

A start control arrangement for a reversible alternating current induction motor, said control arrangement comprising:

• a reversible alternating current split phase induction motor adapted for energization by a voltage signal from an external power supply, said motor including a run winding and a start winding, said run and start windings being electrically connected in parallel;
• first thyristor means electrically connected in series with said run winding;
• second thyristor means electrically connected in series with said start winding;
• control means operative to trigger said first thyristor means into conduction at a predetermined run winding firing angle and to selectively trigger said second thyristor means into conduction at a first predetermined start winding firing angle to initiate motor rotation in one direction and at a second predetermined start winding firing angle to initiate motor rotation in the other direction;
• means for monitoring motor speed and operative to detect when said motor speed exceeds a predetermined running speed threshold;
• said control means being responsive to said monitor means and further operative to inhibit trigger signals to said second thyristor means upon detection of motor speed in excess of said threshold speed, thereby preventing further energization of said start winding once said motor has come up to speed.

A control arrangement for automatically deenergizing the start winding of a split phase induction motor when the running speed of the motor exceeds a predetermined threshold speed, said control arrangement comprising:

• a split phase induction motor adapted for energization by an external voltage supply and including a run winding and a start winding, said run winding being electrically connected in parallel with said start winding;
• thyristor means electrically connected in series with said start winding to control energization of said start winding;
• and
• control means comprising:
• means for selectively triggering said thyristor means into conduction;
• means for repetitively measuring the phase angle between the run current and the line voltage signals;
• memory means for storing one of the phase angle measurements in said memory means as a reference;
• means for comparing subsequent phase angle measurements to said reference and detecting a change of predetermined magnitude between the present phase angle measurement and the reference value the change being representative of motor running speed exceeding the threshold speed;
• and
• means for inhibiting trigger signals to said thyristor means following detection of said change, whereby the start winding is effectively deenergized when the motor reaches running speed.

A control arrangement for automatically deenergizing the start winding of a split phase induction motor when the running speed of the motor exceeds a predetermined threshold speed, said control arrangement comprising:

• a split phase induction motor adapted for energization by an external voltage supply and including a run winding and a start winding, said run winding being electrically connected in parallel with said start winding;
• thyristor means electrically connected in series with said start winding to control energization of said start winding;
• and
• control means comprising:
• means for selectively triggering said thyristor means into conduction;
• means for repetitively measuring the phase angle between the supply voltage signal and the run winding current signal;
• memory means for storing a phase angle measurement measured at a first predetermined time as a reference value;
• means for detecting a first change of a first predetermined magnitude between the present phase angle measurement and the reference value during the time period between said first predetermined time and a second predetermined time and to detect a second change of a second predetermined magnitude between the present phase angle measurement and the reference value thereafter;
• said first and second changes signifying motor speed in excess of a threshold speed;
• and
• means responsive to said detecting means operative to inhibit said trigger means for triggering said thyristor means into conduction following detection of said first or second change, thereby preventing energization of said start winding when said motor has achieved running speed.