Experimental determination of heat transfer co-efficients of salient pole rotors

The author reports on the investigation into the air flow and heat transfer aspects of salient pole rotor cooling. The air flow patterns within the interpolar region and air gap are somewhat speculative and there is very little experimental evidence available to determine their true nature. Moreover, the calculations of heat transfer co-efficients are uncertain because of their linkage with the unknown local air velocity. Cooling mainly takes place from the exposed interpolar faces and the ends of the field coil although some conduction may take place into the pole body and the underneath surface of the pole shoe tip. However, this alternative route via the pole iron to the air gap can be impeded by the magnitude of pole face losses. The object of the investigation was to obtain information which will provide more insight into the aerodynamic and thermal behaviour of a conventionally cooled rotor