The Causes of Under-voltage Fault Alarming and Shutdown in Diesel Generator Set

Aug. 31, 2021

When the generator has no load, the generator will alarm and stop for about 20 seconds after starting up and running, it can be basically judged that the diesel generator will alarm and stop due to failure in under-voltage. There are many reasons for this failure. This article will analyze for you one by one.

 

Recently, Dingbo Power received a repair call from a generator set user, saying that the generator had an under-voltage fault and alarmed and shut down. Dingbo Power immediately arranged for a repairer to come to handle the repair call after receiving the repair call. The maintenance master of our company said that there are many reasons for the under-voltage fault alarm and shutdown of the diesel generator.

 

The Causes of Under-voltage Fault Alarming and Shutdown in Diesel Generator Set



Generator failure phenomenon: The generator set is not loaded, and it will alarm and shut down for about 20 seconds after starting up and running.

 

Causes of issue:

1. The problem of diesel engine generator speed regulation

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 oil volume and oil circuit, which seems to be called a common rail oil pump (forget the specific name). There is a pull rod that controls the amount of oil. For the time being, it is called a speed control rod. There are a speed limit (high speed) ejector rod and a speed control ejector rod on both sides of the speed control rod. If you don’t go, then it can be judged that the speed is not going up. You can try to adjust the speed control ejector. Generally, there is a major fault in the diesel engine set. The major fault is resolved, and a series of secondary faults caused by this will be resolved.

 

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 lower the voltage. If the varistor is broken down or turned on for other reasons, then it can be imagined that the voltage must be very low. There are 6 rectifier bridges. The diode, the tuned DC power supply is used to supply the voltage regulator board and the excitation device. If the rectifier bridge diode is damaged, the role of the voltage regulator board and the excitation device will be greatly reduced.

 

3. Malfunction of generator regulator board

Perhaps due to changes in environmental factors, the parameters of the AVR regulator plate are no longer applicable and need to be re-adjusted. Generally speaking, non-parallel diesel units basically do not have this problem, because the parameters of the regulator plate are fixed values ( 400V). In general, we can’t adjust it. This problem may only occur with the units used for parallel operation, because the AVR 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 regulator board. In this case, either check whether the voltage regulator signal is connected incorrectly, or try to quickly use the electronic controls (parallel device, voltage regulator board, etc.) when starting up. Adjust the voltage.

 

4. The voltage sampling line is loose, and no voltage can be measured at this time.

 

5. Ground fault

If the three-phase grounding is taken out, the voltage and current are very low. At this time, it is necessary to check whether the grounding discharge device (such as the ground knife) is closed or grounded.

 

6. Remanence

If the generator does not have residual magnetization, then the voltage system of the generator cannot be established at the beginning. For this kind of problem, we have to know what V voltage the excitation output of the generator AVR voltage regulator board is, and then put it on the excitation output line Connect the corresponding voltage source for magnetization, pay attention to the corresponding voltage type and do not reverse the polarity.

 

Dingbo Power reminds all users that the faults reasons of different diesel generator sets may be varied. The specific situation still needs to be analyzed and resolved by technicians. It is recommended that users encounter generator failure problems directly contact the after-sales department of the manufacturer for a solution. Dingbo Power is credible experts for maintenance of diesel generator, you can call us for consultation or through email by dingbo@dieselgeneratortech.com. Our technicians are always ready to serve you.


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