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Cause Analysis of Diesel Generator Set's Undervoltage Fault Alarm Shutdown

May 20, 2022
Cause of issue:
       1. Diesel engine generator speed regulation problem
       Diesel engine speed control is divided into electronic speed governor and mechanical speed control. If it is mechanical speed control, then there is an oil pump mechanism on the diesel engine that controls the amount of oil and the oil circuit. It seems to be called a common rail oil pump (forgot what it is called). There is a lever that controls the amount of oil. Let's call it a speed-adjusting lever for the time being. There is a speed-limiting (high-speed) ejector lever and a speed-adjusting ejector lever on both sides of the speed-adjusting lever. After 20 seconds of startup, it will report low pressure. If the voltage and frequency keep going up If it does not go, then it can be judged that it is caused by the inability of the speed to increase. You can try to adjust the speed-adjusting ejector rod. Generally, there is a major failure in diesel engine failures. When the main failure is solved, a series of secondary failures caused by it will be solved. .
       2. The varistor or rectifier bridge diode on the generator winding is damaged
       The function of the varistor is: when an overvoltage fault occurs, the varistor is turned on to reduce the voltage. If the varistor is broken down or turned on for other reasons, it is conceivable that the voltage must be very low, and there are 6 rectifier bridges. Diodes, the set DC power supply is used to supply devices such as voltage regulators and excitation. If the diode of the rectifier bridge is damaged, the functions of voltage regulators and excitation devices will be greatly reduced.
       3. Generator voltage regulator board failure
       Maybe due to changes in environmental factors, the parameters of the AVR pressure regulating plate are no longer applicable and need to be re-adjusted. Generally speaking, this problem is basically not encountered in non-parallel diesel units, because the parameters of the pressure regulating plate are fixed ( 400V), in general, we can't adjust it. Only the units used for parallel operation may have this problem, because the AVR voltage regulator is adjusted according to the main bus voltage during parallel operation. It is not static. At this time, The parallel device generally has a voltage regulating signal sent to the AVR voltage regulating board. In this case, either check whether the voltage regulating signal is connected incorrectly, or try to use the electronic controls (parallel device, voltage regulating board, etc.) Adjust the voltage.
       4. The voltage sampling line is loose, and the voltage cannot be measured at this time.
       5. Ground fault
       If the outgoing line is grounded for three phases, then the voltage and current are very low. At this time, it is mainly necessary to check whether the grounding discharge device (such as the ground knife) is closed or grounded.
       6. Remanence
       If the generator has no remanence, then the voltage system of the generator cannot be built at the beginning. For this problem, we need to know what V voltage is the excitation output of the generator AVR voltage regulation board, and then add the excitation output line to the excitation output line. Connect the corresponding voltage source for magnetization, pay attention to the corresponding voltage type and do not reverse the polarity.
       The above is the analysis of diesel generator set under-voltage fault alarm shutdown. Tingbo Power reminds users that the reasons for the failure of different diesel generator sets may be different. The specific situation still needs to be analyzed and solved in detail. It is recommended that users encounter generator failure problems directly Contact the manufacturer's after-sales department to give a solution.