Performance improvement of integrated starter alternator by changing stator winding connection

A method of controlling an electric machine for use in association with an engine, the electric machine having armature windings and a rotor capable of rotating at various speeds, the method comprising:

• a. connecting the armature windings in a delta connection and operating the electric machine as a cranking motor during engine cranking;
• b. connecting the armature windings in a wye connection and operating the electric machine as a generator after the engine has started and when the rotor is rotating at a low speed;
• and
• c. connecting the armature windings in a delta connection and continuing to operate the electric machine as a generator when the rotor is rotating at a higher electric machine speed.

A method of operating an electric machine for use as both a starter and an alternator in an engine, the electric machine having at least three stator windings and a rotor disposed in proximity to the stator such that the rotor is in electro-magnetic communication with the stator and operable to rotate at a plurality of speeds including a cranking speed, an idle speed, and a winding reconfiguration speed, the method comprising:

• a. providing a plurality of wye switches connected between the three stator windings such that closure of the wye switches will cause the three stator windings to be connected in a wye configuration;
• b. providing a plurality of delta switches connected between the three stator windings such that closure of the delta switches will cause the three stator windings to be connected in a delta configuration;
• c. closing the delta switches so the stator windings are connected in a delta configuration during cranking of the engine;
• d. closing the wye switches so the stator windings are connected in a wye configuration during idle speed;
• and
• e. closing the delta switches so the stator windings are connected in a delta configuration at the winding reconfiguration speed.

An integrated starter and alternator for use with an engine and a crankshaft, the integrated starter and alternator operable at a plurality of speeds including a cranking speed, a low speed, and a winding reconfiguration speed, the integrated starter and alternator operable as a cranking motor for the engine before it starts and operable as a generator driven by the engine after the engine starts, the integrated starter and alternator comprising:

• a. a stator having a plurality of armature windings;
• b. a rotor in electromagnetic communication with the stator and connected to the crankshaft;
• c. means for connecting the armature windings in a delta configuration when the rotor is rotating at the cranking speed and the winding reconfiguration speed;
• and
• d. means for connecting the armature windings in a wye configuration when the rotor is rotating at a low speed.

An integrated starter and alternator for use with an engine, the integrated starter and alternator operable at a plurality of speeds including a cranking speed, a low speed, and a winding reconfiguration speed, the integrated starter and alternator operable as a cranking motor for the engine before it starts and operable as a generator driven by the engine after the engine starts, the integrated starter and alternator comprising:

• a. a stator having a plurality of armature windings;
• b. a rotor in electromagnetic communication with the stator and connected to the engine by a belt;
• c. means for connecting the armature windings in a delta configuration when the rotor is rotating at the cranking speed and the winding reconfiguration speed;
• and
• d. means for connecting the armature windings in a wye configuration when the rotor is rotating at a low speed.