Modern motors use higher electromagnetic loads to impro […]
Modern motors use higher electromagnetic loads to improve the utilization of materials, and the single-machine capacity of the motor is also increasing. Therefore, the cooling system of the motor must be improved to improve its heat dissipation capability. Except for some small or special motors, most motors use a fan to force air flow to cool the motor.
As early as 1928, the synchronous camera used to improve the power factor of the power network succeeded in using hydrogen as a cooling medium. Tests have shown that the motor of the same size can increase the capacity by 20 to 25% or more by using hydrogen cooling, and the efficiency is also improved, because the mechanical friction loss of the gas is reduced and the heat dissipation capability is improved. Since then, steam turbine generators have been rapidly promoted using hydrogen cooling technology. After the 1950s, internal cooling systems were used in large-capacity motors, especially turbo generators. The so-called internal cooling is to transfer the heat generated in the conductor directly to the cooling medium without passing through the insulation. Initially, hydrogen was commonly used as a cooling medium in internal cooling systems. Later, in order to further improve the cooling capacity, liquid (water or oil) was used as a cooling medium.
It is convenient to divide the cooling system of the motor according to the difference of the cooling medium. Currently the most widely used in motor manufacturing is air cooling systems that use air as a cooling medium. This chapter mainly describes the air cooling system. For the cooling system using other media, we will discuss the timing.