Researches on vibration characteristics of cracked rotors were summarized.On this basis

combined with the field vibration fault diagnosis for two 600MW unit turbines

the typical cracked rotor's vibration characteristics of practical turbine generator set were presented

such as:the vibration amplitudes continuously rises and most of them are unstable synchronous vibration

they only exhibit obvious 2 Xvibration when the crack is deep enough;the linearity of response to dynamic balance weight is poor

and the influence coefficient and lag angle is different from that of the normal rotor;the vibration intensifies with the unit load

but it can not turn back to the original value when the unit load decends.Therefore

it suggests that early crack be found in time through flaw detection.