One application for water-cooled motors has been in testing scale models of airplane designs. The motor drives the propeller while technicians check lift, drag, movement, and so forth. In this case, the water-cooled version got the nod because of its small size. Water-cooled motors have also found a spot driving pumps to cool nuclear reactors. Mining and tunnel drilling are candidate uses as well.
The average horsepower-per-pound for a water-cooled motor is 1.9. In contrast, the average for a still-air-cooled motor is 0.3 hp/lb. Water-cooled units can range in output from about 2 to 2000 hp or more. Their physical size can be 2 inches diameter on the low end to about 50 inches or more. Size, of course, depends on the application.
Water-cooled motor designs have many of the same components found in ordinary induction motors. But the design of the various components can be quite different.
Water-cooled induction motors can be much smaller than air-cooled versions with the same rating. The water-cooled 10-hp motor (right) has a 2.5-in diameter. In contrast, the conventional 10-hp unit (left) has a 5.5-in. diameter.
Probably the most obvious difference in construction is the water jacket. The motor water jacket consists of a housing, ribs, cover, two water connectors, and two seals. Water hoses connect to the inlet and outlet connectors. the staggered ribs force water to circulate between the motor and housing. In addition, water-cooled motors have a heat shield surrounding the bearings on their shaft.
