Stacked coil assembly for a stator

The present invention relates to a stacked coil assembly for a stator, and more particularly, to a stator of an electric rotary machine. The present invention provides a coil assembly comprising at least two end coil pieces having a U-shaped end and an open end, the open end comprising a first end and a second end, the second end having a terminal length greater than the first end, and at least one middle coil piece is provided stacked between the end coil pieces having a U-shaped end and an open end, the open end comprising third ends having a terminal length equal to the first end, and at least two intermediate coil pieces each being separately stacked between the end coil piece and the intermediate coil piece having a U-shaped end and an open end, the open end comprising fourth ends having a terminal length shorter than the first and third ends with the first and third ends being connected to an adjacent fourth end.