Fault Analysis Of Rotating Rectifier Of Synchronous Generator

1、 Symptoms.

Rotating rectifier is usually a rectifier circuit composed of silicon rectifier elements. If one or more rotating silicon elements in the circuit are damaged, the damaged silicon elements will lose unidirectional conductivity (both forward and reverse directions are conductive), resulting in a short circuit of rotating silicon elements in the circuit. When the unit is running, the generator has no output voltage. If the fault is not found and eliminated in time. It will cause the AC exciter armature winding to burn out and the generator will be forced to stop.

2、 Cause of failure.

① Rotating rectifier silicon rectifier diode is damaged due to overvoltage or overcurrent.

② The torsional moment of the silicon rectifier element of the rotating rectifier is too large during installation, resulting in the deformation of the tube shell and the damage of the internal silicon chip.

③ The load power factor is too low, which causes the excitation current to exceed the rated current of the silicon rectifier element for a long time and damages it.

3、 Treatment method.

① Rotating silicon elements shall be equipped according to the current level specified in the drawing. If there is no drawing data at hand, the silicon element of standard specification can be close to the excitation current value of the main generator. At present, the common specifications of rotary rectifiers produced in China include 16A, 25A, 40A, 70A and 200A.

② The voltage level of rotating silicon element shall be reasonably selected. The reverse peak voltage URN of rotating silicon element shall be~15 times the excitation voltage UIN

③ Tighten the nuts of rotating silicon elements with proper torque, and use a constant torque wrench to tighten the nuts. The torque value for tightening the nuts of rotating silicon elements shall be as specified in Table 3-4.

④ Take overvoltage protection measures. Overvoltage protection is usually equipped with a varistor or a resistance-capacitance absorption circuit at the DC side of the rotating rectifier.

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