Solution to The Low Operating Frequency of Diesel Generator Set at 45Hz

Both too high and too low frequencies can have an impact on diesel generator sets. After the diesel generator starts, the generator generates electricity, but the power generation frequency can only reach 45Hz. What exactly is going on? Today, Dingbo Power, a diesel generator manufacturer, will discuss this common fault with our users. The superficial cause of this fault is a problem with the generator or its control section. In fact, when the rotational speed of the diesel engine fails to reach the rated speed, the power generation frequency cannot reach 50Hz. This is a fault in the diesel engine's fuel supply system or a mechanical issue of the diesel engine.

Reasons for the low power generation frequency (only up to 45Hz) of the generator

One or several cylinders of the diesel engine are not working well or not working at all.

The low-pressure fuel pipeline is partially blocked.

The fuel supply of the high-pressure fuel pump does not meet the specified requirements of this machine, or some individual plungers inside the high-pressure fuel pump are stuck.

There is air in the fuel pipeline.

For a diesel engine after major repair, the connecting rod bolts are tightened too forcefully, resulting in an overly tight fit between the connecting rod bearing and the journal.

The fuel transfer pump is not working properly.

Some fuel injectors do not inject fuel.

Troubleshooting methods for the low power generation frequency (only up to 45Hz) of the generator

Start the diesel engine until the rotational speed reaches about 700 r/min. Touch the exhaust pipes of each cylinder by hand. If the exhaust temperatures of all 6 cylinders are basically the same, it indicates that each cylinder is working properly, and the possibility of individual cylinders not working well or not working can be ruled out.

After shutting down, check the inlet filter screen of the fuel transfer pump. If there are no impurities in the filter screen, it can be said that it is working normally.

Conduct an oil pressure test on the fuel transfer pump. First, remove the outlet pipe of the fuel transfer pump. Then, block the outlet hole of the fuel transfer pump with your left hand and repeatedly press the handle of the fuel transfer pump with your right hand to conduct an oil pressure test on the fuel transfer pump. Through inspection, the oil pressure of the fuel transfer pump outlet is basically normal, but diesel is dripping from the oil inspection tube of the high-pressure fuel pump.

After reinstalling the outlet pipe of the fuel transfer pump, remove the side cover of the high-pressure fuel pump. Then start the diesel engine and observe whether diesel is leaking from the joint between the plunger and the pump body inside the high-pressure fuel pump. During the inspection by the diesel generator manufacturer, no oil leakage is found. Then it can only be assumed that during operation, diesel seeps into the high-pressure fuel pump body through the gap between the plunger and the plunger sleeve of the fuel transfer pump. This causes insufficient fuel supply in the low-pressure fuel pipeline, reducing the power of the diesel engine and preventing the rotational speed from reaching the rated speed.

After replacing the fuel transfer pump, start the diesel engine and increase the rotational speed of the diesel engine. After the control handle reaches the specified maximum rotational speed requirement, observe from the tachometer that the rotational speed is 1,510 r/min. Excite the exciter. The generator generates electricity and the frequency meter shows 50.5Hz. When the rotational speed is reduced until the generator frequency is 50Hz, supply power to the equipment. Everything is normal and the fault is eliminated.

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