Abstract: The reasons of the generator fault were introduced. It was expounded that in fault treatment process, the dynamic balance test of the generator must be carried out on the scene only, and in order to reduce the urgent repair time, it was decided to start the generator with pressed air cooling instead of hydrogen cooling and to carry out the dynamic balance test further, which is a method never adopted for the generator of 9F unit in our country. The practical result shows that the temperature of each part of the generator is normal, and the indexes are all in the standard range, and this means that the air cooling startup of generator 390H was successful; and better effect was obtained.

Key words: generator 390H, startup with air cooling, dynamic balance test, matters needing attention