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Diesel generator technical questions and answers 1-20

Diesel generator technical questions and answers (1-20)

1. What are the conditions for the use of two generator sets in parallel? What device to complete the parallel operation?

Answer: The conditions for parallel use are the same voltage, frequency, and phase of the two machines. Commonly known as "three simultaneous." Use a dedicated parallel device to complete the parallel operation. It is generally recommended to use a fully automatic cabinet. Try not to manually merge. Because the success or failure of manual paralleling depends on human experience. The author has ventured over 20 years of experience in electric power work. The reliable success rate of manual parallel diesel generators is equal to zero. Never use the concept of manual parallelism in the mains power system to apply a small power system, because the protection level of the two is completely different.

2. Why does the generator room have to be clean and free of floating sand on the ground?
A: If the diesel engine inhales dirty air, the power will drop; if the generator inhales impurities such as sand, it will cause insulation damage between the stator and rotor gaps, resulting in burning.

3. Why do we require the customer to perform a tightening of all electrical contact parts after every 200 hours of operation of the unit?
A: The diesel generator is a vibration machine. And many domestically produced or assembled units do not use double nuts. The use of spring washers is useless. Once the electrical fasteners are loosened, a large contact resistance is generated, resulting in abnormal operation of the unit.

What is the power factor of the three-phase generator? Can a power compensator be added to increase the power factor?
A: The power factor is 0.8. No, because the charging and discharging of the capacitor can cause fluctuations in the small power supply. And the unit is oscillating.

5. Why did our company generally not recommend users to use neutral point grounding during installation since 2002?
Answer: 1) The self-regulating function of the new generation generator is greatly enhanced;
2) In practice, it has been found that the lightning fault rate of neutral grounding units is high.
3) The grounding quality is high and the average user cannot do it. Unsafe grounding is not as good as grounding.
4) The neutral grounded unit will cover the load leakage faults and ground faults, and these faults and errors cannot be exposed under the mains power supply condition.

6. How can UPS and diesel generators be matched in order to ensure that the UPS output is stable?
Answer: 1) UPS is generally expressed by the apparent power KVA, which is first multiplied by 0.8 and converted into a unit KW that is consistent with the active power of the generator.
2) If a general generator is used, multiply the active power of the UPS by 2 to determine that the generator power, ie the generator power, is twice the UPS power.
3) If a PMG (permanent magnet machine excitation) generator is used, the power of the generator is determined by multiplying the power of the UPS by 1.2, that is, the generator power is 1.2 times the UPS power.

7. What should be taken care of when using neutral ungrounded units?
Answer: The 0 line may be live because the capacitor voltage between the live line and the neutral point cannot be eliminated. The operator must see the 0 line as a live body. Can not be treated according to commercial power.

8. Do you indicate the electronic or electrical components with a withstand voltage of 500V that can be used for a diesel generator control cabinet?
A: No. Because the 400/230V voltage marked on the diesel generator set is an 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. How to identify fake and counterfeit domestic diesel engines?
Answer: First check whether there is a factory certificate and a product certificate. These are the "identity certificates" of the diesel engine. They must be there. Re-check the three major serial numbers on the certificate: 1) the nameplate number; 2) the body number (which is generally on the mechanically machined surface of the flywheel, the font is convex); 3) the oil pump nameplate number. Checking these three numbers with the actual number on the diesel engine must be accurate. If there are any doubts, these three major numbers can be reported to the manufacturer for verification.

10. Are all diesel generator sets self-protected?
A: No. At present, there are even some belts in the same brand of units on the market. The user must know for himself when purchasing the unit. It is best to write a written document as an attachment to the contract. General low-priced machines do not have self-protection function.

11. What regulations does the State require that the engine power of a general generator set should be greater than the generator power? Answer: 10c/o.

12. Some generator engine power is expressed in horsepower. How does horsepower and international unit kilowatts convert?
Answer: 1 horsepower = 0.735 kilowatts, 1 kilowatt = 1.36 horsepower.

13. How to calculate the current of three-phase generator?
Answer: I = P / (√3 Ucos φ )
That is, current = power (watts) / (√3 * 400 (volts) * 0.8).
The simplified calculation formula is: I(A) = unit rated power (KW)* 1.8

14. After operating the electrician to take over the diesel generator set, what are the three main points to verify?
Answer: 1) Verify the unit's true useful power. Then determine the economic power, and standby power. The method for verifying the true useful power of the unit is: a diesel engine's 12-hour rated power multiplied by 0.9 to obtain a data (kw). If the rated power of the generator is less than or equal to the data, the rated power of the generator is used as the actual useful power of the unit. If the rated power of the generator is greater than the data, the data must be used as the actual useful power of the unit.
2) Verify what kind of self-protection features the unit has.
3) Verify whether the power wiring of the unit is qualified, whether the protective grounding is reliable and whether the three-phase load is basically balanced.

15, there is an elevator starter motor 22KW, should be equipped with how much generator?
A: 22 * 7 = 154KW (the elevator is a direct load-start model, the instantaneous starting current is generally 7 times the rated current, in order to ensure that the elevator for uniform motion). (ie at least 154kW generator set)

16. How to calculate the optimal power (economic power) of the generator set?
Answer: P best = 3/4*P rated (ie 0.75 times rated power).

17. What is the relationship between apparent power, active power, rated power, maximum power, and economic power?
Answer: 1) The unit of apparent power is KVA. China is used to express the capacity of transformers and UPS.
2) The active power is 0.8 times the apparent power. The unit is KW. China is accustomed to power generation equipment and electrical equipment.
3) The rated power of a diesel generator refers to the power that can be continuously operated 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 of the diesel generator set that can operate for a long time without time limitation. At this power operation, the fuel is the most economical and the failure rate is the lowest.

18. Why can't the diesel generators be allowed to operate for a long period of time under 50% of the rated power?
A: The increase in oil consumption, diesel engine is easy to coke, increase the failure rate, shorten the overhaul cycle.

19. What is the problem of loss of magnetization of a generator and how should it be handled?
Answer: The generator will not be used for a long time, causing the residual magnetism contained in the iron core to be lost before leaving the factory. The excitation coil cannot build up the required magnetic field. At this time, the engine is running normally but no power is available. This phenomenon is new. Or there are more units that are not used for a long time. Processing methods: 1) Press the excitation button with the excitation button, 2) Excitation button, charge it with the battery, 3) With a light bulb load, speeding for a few seconds.

20. After using the generator set for a period of time, it was found that everything else was normal but the power was decreasing. What was the main reason?
Answer: a. The air filter is too dirty to suck in enough air. 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. It must be replaced or cleaned. c. The ignition timing is not correct and must be adjusted.


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