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Technical Questions And Answers About Diesel Generators (3)
2021-11-18 13:54:03

16. How to calculate the current of a three-phase generator?

Answer: I = P / (√3 Ucos φ) That is, current = power (watts) / (√3 *400(volt) * 0.8).

The simplified formula is: I (A) = unit rated power (KW) * 1.8

17. What is the relationship between apparent power, active power, rated power, maximum power, and economic power?


1) The unit of apparent power is KVA, which is used to express the capacity of transformers and UPS in our country.

2) The active power is 0.8 times the apparent power, the unit is KW. my country is used to power generation equipment and electrical equipment.

3) The rated power of a diesel generator set refers to the power that can be operated continuously for 12 hours.

4) The maximum power is 1.1 times the rated power, but only 1 hour is allowed within 12 hours.

5) The economic power is 0.75 times the rated power, which is the output power that the diesel generator set can run for a long time without time limitation. When running at this power, the fuel is the least and the failure rate is the lowest.

18. Why is it not allowed for diesel generator sets to run for a long time when the power is less than 50% of the rated power.

Answer: Increased oil consumption makes diesel engines prone to carbon formation, which increases the failure rate and shortens the overhaul period.

19. The actual output power of the generator during operation is based on the wattmeter or the ammeter?

Answer: The ammeter shall prevail, and the power meter is for reference only.

20. The frequency and voltage of a generator set are both unstable. Is the problem with the engine or the generator?

Answer: It lies in the engine.

21. The frequency of a generator set is stable, but the voltage is unstable. The problem is the engine or the generator?

Answer: It lies in the generator.

22. What is the loss of magnetism of the generator and how to deal with it?

Answer: The generator is not used for a long time, causing the remanence contained in the iron core to be lost before leaving the factory, and the excitation coil cannot build the proper magnetic field. At this time, the engine is running normally but no electricity is generated.

This kind of phenomenon is a new machine. Or there are more units that have not been used for a long time.


1) Press the excitation button once if there is an excitation button,

2) if there is no excitation button, use a battery to magnetize it,

3) load a light bulb and run it at overspeed for a few seconds.

23. After the generator set has been used for a period of time, it is found that everything else is normal but the power drops. What is the main reason?

Answer: a. The air filter is too dirty and the intake air is not enough. At this time, the air filter must be cleaned or replaced. b. The fuel filter device is too dirty and the fuel injection volume is not enough, so it must be replaced or cleaned. c. The ignition time is not correct and must be adjusted.

24. After a generator set is loaded, its voltage and frequency are stable, but the current is unstable. What is the problem?

Answer: The problem is that the customer's load is unstable, and the quality of the generator is absolutely fine.

25. The frequency of a generator set is unstable. What is the main problem?

Answer: The main problem lies in the unstable speed of the generator.

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