The impeller (one) is rotated because of the crankshaft and it converts the mechanical Power in the crankshaft into kinetic Electrical power by putting the fluid in movement. With the three-passage torque converter, two passages are utilized for transmission oil (ATF) circulation in the torque converter and for clutch cooling, https://torque-converter-clutch38257.thenerdsblog.com/39760723/the-best-side-of-torque-converter-clutch