In the related art, motors (three-phase motors) that are driven in three phases have been widely used. In general three-phase motors, coils of respective phases are connected to each other at neutral positions thereof, and electric currents are not independently applied to the coils of the respective phases.
In contrast, an invention of an electric power steering apparatus equipped with a motor having a connection relationship in which coils of respective phases can be independently driven is disclosed (for example, refer to Patent Document 1). If the coils of the respective phases can be independently driven, a larger torque can be output as compared to the case where the coils of the respective phases are connected to each other.
On the other hand, the applicability of motors has also increased. For example, an invention of a motor generator that functions as a starter motor at the time of starting an engine and functions as a generator after the engine is started is disclosed (refer to Patent Document 2). The motor generator of such an aspect may be referred to as an alternating current generator (ACG) starter. By using the ACG starter, the need for including a related-art cell motor type starter disappears. For this reason, weight and costs can be reduced, and generation of noise caused by a reduction gear that couples a cell motor type starter and a crankshaft together can be eliminated. Particularly, in vehicles that perform idling stop, which have recently become more common, the ACG starter is preferably used because mechanical noise at the time of the starting of the engine is suppressed.