Load and speed sensitive motor starting circuit and method

A circuit and method measures main motor winding voltage and detects points in the electromagnetic wave cycle where this voltage "crosses" zero. It also measures auxiliary motor winding voltage. Phase shifts measured in the auxiliary winding are compared as a means for starting and restarting the auxiliary winding. The points in the electromagnetic wave cycle where the current in the auxiliary winding "crosses" zero are detected and compared with a first window pulse that is generated when the main voltage crosses zero. When the zero current crossing points fall outside the first window pulse, the auxiliary winding is disconnected. The points where the voltage in the auxiliary winding "crosses" zero are also detected and compared with a second window pulse that is generated when the main voltage crosses zero. When the zero voltage crossing points fall within the second window pulse, the auxiliary winding is switched back into the circuit.