On-line Detection Method Of Typical Faults In Rotating Rectifier System Of The Brushless Exciter

As a key component of the brushless exciter,the rotary rectification system is also a weak link in the stable operation of the brushless exciter.The brushless exciter rotary rectification system rotates synchronously with the generator rotor.Under high load,overvoltage and strong vibration working conditions,diode open-circuit faults occur,which brings safety hazards to the generator excitation system.When the number of diodes is large,the exciter can not be properly excited,resulting in the generator not working properly.Therefore,it is particularly important to propose a method for detecting typical faults in brushless excitation online.The main work of this paper is as follows:(1)Calculate the conduction law of the armature winding in the normal and open-circuit faults of the brushless exciter rotating rectifier system diode,analyze the variation law of the typical fault feature quantity,and lay the theoretical basis of the online detection of the brushless exciter rotary rectification typical failures.(2)The module structure of the rotating rectification system is introduced.The 5.8MW three-phase brushless exciter of a power plant and the 11-pole 39-phase brushless exciter are studied.The brushless exciter based on field-circuit coupling is established.The two-dimensional finite element simulation model verifies the correctness of the model.(3)A new fault diagnosis method is proposed: U-shaped detection coil method,and the variation of magnetic flux and induced voltage in U-shaped detection coil under health and fault conditions of three-phase and multi-phase brushless exciter are studied.Regularity,the characteristics of harmonic frequency are analyzed,and a new fault criterion is proposed,which can be used as a diagnostic method for the fault of the rotating rectification system of brushless exciter.(4)The above U-shaped detection coil method is improved,and another new fault diagnosis method is proposed: double U-shaped detection coil method,and the three-phase brushless exciter is studied under normal and fault conditions.The variation law of the air gap flux density is analyzed,and the induced vol tage difference of the double U-shaped detection coil is calculated.Another new fault criterion is proposed for the fault diagnosis of the brushless exciter.