Water levels in open wells or tanks can fluctuate widely, so these types of pumps are ideal. It is designed to work under water and is located at the bottom of the well. This machine is powered by a rewindable and water-cooled prime mover. Using water-lubricated bearings and a synthetic film insulation on the winding wires in the stators helps minimise wear. Assembling the silicon steel laminates under pressure and locking them together rigidly reduces energy loss.