Stator with circumferential cooling channels and parallel passages between slots

A method of cooling a stator, the method comprising:

• flowing coolant through first and second set(s) of passage(s) in the stator;
• wherein the stator includes:
• an annular housing extending around a central axis;
• a first circumferential flow channel extending around the housing;
• a second circumferential flow channel axially spaced from the first circumferential flow channel and extending around the housing;
• and
• a plurality of windings;
• wherein the plurality of windings are circumferentially spaced about the housing to form a passage between each two adjacent windings;
• wherein each passage is in fluid communication with both the first circumferential flow channel and the second circumferential flow channel;
• wherein the first circumferential flow channel is closed to flow at a first circumferential location and the second circumferential flow channel is closed to flow at a second circumferential location, removed from the first circumferential location, so as to form the first set of passages connected in parallel and the second, separate set of passages connected in parallel;
• and
• wherein the stator is configured such that coolant flows through the first set of passages from the first circumferential flow channel to the second circumferential flow channel and then flows from the second circumferential flow channel through the second set of passages to the first circumferential flow channel;
• the stator further comprising:
• a first insert configured to close the first circumferential flow channel to flow at the first circumferential location;
• and
• a second insert configured to close the second circumferential flow channel to flow at the second circumferential location.