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Fault Analysis of Voltage Instability After Starting Diesel Generators

Sep. 25, 2023

After the diesel generators generate electricity, unstable voltage and frequency faults are generally caused by unstable excitation current or low residual excitation voltage of the exciter. When the excitation current of a diesel generator is unstable or the residual excitation voltage of the exciter is low, the rotor rotates and the AC voltage generated by the cutting force line of the stator becomes unstable, resulting in frequency fluctuations.


diesel generator set


1. After starting the diesel engine, increase the speed and check if the voltage and frequency are stable. With the progress of speed, the voltage and frequency are not firmly planned, but the diesel engine has stabilized and the exhaust smoke is light gray. This indicates that the diesel engine is working normally, and the problem may be in the control box and exciter.


2. Using a multimeter to measure the exciter and related circuits, no abnormalities were found


3. The stability of the AVR control board was adjusted, but the problem was not resolved


4. After the diesel generator stops, use a 6V battery to magnetize the exciter, and then start the diesel engine until the speed reaches around 750r/min. The diesel generator begins to build voltage, and the unstable planning of voltage and frequency meets the skill requirements of the diesel generator.


5. After stopping the engine, restart the diesel engine and check the frequency and voltage of the diesel generator for any feedback. It was found that the frequency and voltage are unstable again


6. After shutdown, increase the starting speed of the diesel engine (increase the fuel supply of the governor), and restart the diesel engine until the speed reaches around 800r/min. At this time, the frequency and voltage of the diesel generator are stable. But when the operating handle was lowered to start the diesel engine, it was found that the frequency and voltage of the diesel generator were unstable. After several repetitions, it was concluded that the starting speed of the diesel engine of this diesel generator must be between 750-800 r/min before the diesel generator can generate electricity, and the voltage and frequency are not firmly planned to meet the requirements.


The above content is the fault analysis of unstable voltage and frequency after starting diesel generators organized by Dingbo Power Generation Equipment, for the reference of users.


Guangxi Dingbo Power Equipment Manufacturing Co.,Ltd was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. The company has a registered capital of 218.88 million yuan. The company covers an area of 86,000 square meters and a building area of 55,000 square meters. There are more than 660 employees, including 456 professional technicians and 106 senior technicians. It has 46 sales and service outlets nationwide. The main products are diesel engines, generator sets, and diesel generators, providing users with a one-stop service of design, supply, debugging and maintenance at any time. Dingbo has always insisted on using first-class talents, building first-class enterprises, manufacturing first-class products, creating first-class services, and making every effort to build a first-class domestic enterprise. If any question please feel free to visit our website https://www.dieselgeneratortech.com/ or send email to sales@dieselgeneratortech.com.

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