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Technical Questions And Answers About Diesel Generators (2)
2021-11-09 10:41:16

6. What problems should be paid attention to when using the unit with ungrounded neutral point?

Answer: The 0 line may be charged because the capacitor voltage between the live line and the neutral point cannot be eliminated. The operator must regard the 0 line as a charged body. It cannot be handled according to utility power habits.

7. How to match the power of UPS and diesel generator to ensure stable output of UPS?


1) UPS is generally expressed in apparent power KVA, first multiply it by 0.8 and convert it to the unit KW which is consistent with the generator's active power.

2) If a general generator is used, the active power of the UPS is multiplied by 2 to determine the power of the generator, that is, the power of the generator is twice the power of the UPS.

3) If a generator with PMG (permanent magnet machine excitation) is used, the UPS power is multiplied by 1.2 to determine the generator power, that is, the generator power is 1.2 times the UPS power.

8. Can electronic or electrical components marked with a withstand voltage of 500V be used in diesel generator control cabinets?

Answer: No. Because the 400/230V voltage marked on the diesel generator set is the effective voltage. Its peak voltage is 1.414 times the effective voltage. That is, the peak voltage of the diesel generator is Umax=566/325V.

9. Do all diesel generator sets have self-protection function? Answer: No. At present, there are even some units of the same brand in the market, and some do not. The user must figure it out by himself when purchasing the unit. It is best to write in written materials as an attachment to the contract. Generally, low-cost machines do not have self-protection function.

10. How to identify fake, inferior and counterfeit domestic diesel engines?

Answer: First check whether there is a factory certificate and a product certificate. These are the "identity certificates" for the diesel engine to leave the factory and are required. Check the three major numbers on the certificate again:

1) nameplate number;

2) body number (the actual product is usually on the plane machined at the flywheel end, the font is convex);

3) the oil pump nameplate number.

Check these three numbers with the actual numbers on the diesel engine, and they must be accurate. If any doubts are found, these three numbers can be reported to the manufacturer for verification.

11. After the operating electrician takes over the diesel generator set, which three points must first be verified?


1) Verify the real useful power of the unit. Then determine the economic power and reserve power. The method of approving the real useful power of the unit is: the 12-hour rated power of the diesel engine is multiplied by 0.9 to obtain a data (kw). If the rated power of the generator is less than or equal to this data, the rated power of the generator is regarded as the real useful power of the unit. If the rated power of the generator is greater than this data, this data must be used as the real useful power of the unit.

2) Verify which self-protection functions the unit has.

3) Check whether the power wiring of the unit is qualified, whether the protective grounding is reliable, and whether the three-phase load is basically balanced.

12. There is an elevator starting motor of 22KW, what size generator set should it be equipped with?

Answer: 22*7=154KW (the elevator is a direct load starting model, and the instantaneous starting current is generally 7 times the rated current to ensure that the elevator moves at a constant speed). (That is, it should be equipped with a generator set of at least 154KW)

13. How to calculate the optimal power (economic power) of the generator set?

Answer: P is best = 3/4*P rated (that is, 0.75 times the rated power).

14. According to the national regulations, how much higher the engine power of a general generator set should be than the generator power?

Answer: 10℅.

15. The engine power of some generator sets is expressed in horsepower. How to convert horsepower to international unit kilowatts?

Answer: 1 horsepower = 0.735 kilowatts, 1 kilowatt = 1.36 horsepower.

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