Reasons for damage of rectifier diode, replacement and selection — SUNMATE

Reasons for damage of rectifier diode, replacement and selection

(1) Inadequate lightning protection and overvoltage protection measures. The rectifier device is not provided with lightning protection and overvoltage protection devices. Even if lightning protection and overvoltage protection devices are provided, their operation is unreliable and the rectifier tube is damaged due to lightning stroke or overvoltage.

(2) Poor operating conditions. For the indirectly driven generator set, due to the incorrect calculation of the speed ratio or the ratio of the diameters of the two belt pulleys does not meet the requirements of the speed ratio, the generator operates at high speed for a long time, and the rectifier works at high voltage for a long time, which promotes the accelerated aging of the rectifier and is damaged prematurely.

(3) Poor operation management. The operator on duty is irresponsible, does not understand the change of external load (especially between 0:00 PM and 6:00 am the next day), or when the external load shedding fault occurs, the operator does not carry out corresponding operation and treatment in time, resulting in overvoltage and breakdown and damage of the rectifier.

(4) Poor equipment installation or manufacturing quality. Because the generator set has been operating in large vibration for a long time, the rectifier is also under the external force interference of this vibration; At the same time, due to the high and low speed of the generator set, the working voltage borne by the rectifier also changes from high to low, which greatly accelerates the aging and damage of the rectifier.

(5) The specification and model of rectifier tube are inconsistent. When replacing a new rectifier tube, the tube whose working parameters do not meet the requirements is replaced by mistake or the wiring is wrong, resulting in the breakdown and damage of the rectifier tube.

(6) The safety margin of rectifier tube is too small. The safety margin of overvoltage and overcurrent of rectifier tube is too small, so that the rectifier tube can not withstand the attack of overvoltage or overcurrent transient process peak in generator excitation circuit.

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Inspection method

First, remove all the rectifier diodes in the rectifier and use the 100 of the multimeter × R or 1000 × R ohm gear, measure the two outgoing lines of rectifier diode (head and tail are adjusted and measured once respectively). If the two measured resistance values differ greatly, for example, the resistance value is as high as hundreds of K Ω to infinity, while the resistance value is only hundreds of Ω or even smaller, it indicates that the diode is good (except for the diode with soft breakdown). If the two measured resistance values are almost equal and the resistance value is very small, it indicates that the diode has been broken down and damaged and cannot be used. If the resistance measured twice is infinite, it indicates that the diode has been internally disconnected and cannot be used.

substitution

After the rectifier diode is damaged, it can be replaced by the rectifier diode of the same model or other models with the same parameters.

Generally, the rectifier diode with high withstand voltage value (reverse voltage) can replace the rectifier diode with low withstand voltage value, while the rectifier diode with low withstand voltage value cannot replace the rectifier diode with high withstand voltage value. The diode with high rectifier current value can replace the diode with low rectifier current value, while the diode with low rectifier current value cannot replace the diode with high rectifier current value.