Since the suction type cold air is first in contact wit […]
Since the suction type cold air is first in contact with the heat generating portion of the motor, and a larger diameter fan can be used, the press-in type cooling air is first passed through the fan, heated by the loss of the fan, and then contacted with the heat generating portion of the motor ( In high-speed motors, the air temperature rise caused by fan loss can reach about 5 °C, so the suction type cooling capacity is high.
In the DC motor, the fan is installed at the non-commutator end. For example, the press-in cooling system can prevent the carbon powder that the brush wears from entering the motor. However, most of the air volume is blown through the stator inter-electrode space, and the rotor is blown. The air volume is small, which makes it difficult to dissipate the rotor with more loss. At this time, appropriate measures should be taken to dissipate heat.
Air-cooled systems generally use external cooling or so-called surface cooling, but in order to improve the cooling capacity, there are also internal cooling methods, such as the excitation winding of a hydro-generator, which can be air-cooled. Foreign air cooling has also been used on rotor windings of turbo generators with small capacity. However, the internal cooling system is complicated in structure and requires very clean cooling gas, so it is rarely used in motors that use air as a cooling medium.