Get Knowledge of Common Diesel Engine Generator Sets

As for the basic technical knowledge of common generator, diesel engine and set, we popularized it in the form of question and answer a few years ago, and now it is repeated at the request of some users. As each technology has been updated and developed, the following contents are for reference only:

1. Which six systems are included in the basic equipment of diesel generator set?

A: (1) fuel lubrication system; (2) Fuel system; (3) Control and protection system; (4) Cooling and radiation system; (5) Exhaust system; (6) Starting system;

2. Why do we recommend fuel recommended by professional companies in our sales work?

A: fuel is the blood of the engine. Once the customer uses unqualified fuel, serious accidents such as bearing shell biting, gear tooth cutting, crankshaft deformation and fracture will happen to the engine until the whole machine is scrapped. Specific fuel selection and usage precautions are detailed in the relevant articles in this edition.

3. Why does the new machine need to change the fuel and fuel filter after a period of time?

A: During running-in period, impurities inevitably enter the fuel pan, causing physical or chemical deterioration of the fuel and fuel filter. After-sales customer service and contract process of sets sold by Wuhan Jili, we will have professional staff to carry out relevant maintenance for you.

4. Why do we require the customer to tilt the exhaust pipe down 5-10 degrees when installing the set?

A: It is mainly to prevent rainwater from entering the smoke pipe, leading to major accidents.

5. Manual fuel pump and exhaust bolt are installed on general diesel engine. What is their function?

A: To remove air from the fuel line before starting.

6. How is the automation level of diesel generator set divided?

A: Manual, self-startup, self-startup plus automatic power conversion cabinet, remote three remote (remote control, remote measurement, remote monitoring).

7. Why is the output voltage standard of the generator 400V instead of 380V?

A: Because there is a loss of voltage drop in the line after it goes out.

8. Why is it required that the use site of diesel generator set be air-smooth?

A: The output of the diesel engine is directly affected by the quantity and quality of air being sucked in. In addition, the generator must have sufficient air for cooling. Therefore, the use of the site must be air-smooth.

9. Why should not the above three sets be screwed too tightly with tools when installing fuel filter, diesel filter and fuel-water separator, but only by hand to avoid fuel leakage?

A: Because if the sealing ring is screwed too tightly, it will expand under the action of fuel bubbles and body temperature rise, resulting in great stress. Damage to the filter housing or separator housing itself. What is more serious is the damage to the body dysprosium which cannot be repaired.

10. How to distinguish between counterfeit and fake domestic diesel engines?

A: It is necessary to check whether there are manufacturer’s certificates and product certificates, which are the “identification certificates” of the diesel engine manufacturer. Check the three major numbers on the certificate 1) Nameplate number;

2) Airframe number (typeface is convex on machined plane of flywheel end in kind); 3) Name plate number of fuel pump. The three major numbers must be correctly checked against the actual numbers on the diesel engine. If any doubts are found, these three numbers can be reported to the manufacturer for verification.

11. After the electrician takes over the diesel generator set, which three points should be checked first?

A: 1) Verify the true useful power of the set. Then determine the economic power and backup power. The method to verify the true useful power of the set is to multiply the 12-hour rated power of the diesel engine by 0.9 to get a data (kw). If the rated power of the generator is less than or equal to this data, then the rated power of the generator is set as the true useful power of the set. If the rated power of the generator is greater than this data, this data must be used as the true useful power of the set.

2) Verify the self-protection functions of the set. 3) Verify whether the power wiring of the set is qualified, whether the protection grounding is reliable and whether the three-phase load is basically balanced.

12. One elevator starter motor is 22KW. What size generator set should it be?

A: 22*7=154KW (elevator is directly loaded starter, instantaneous startup current is usually 7 times of rated current).

Only then can the elevator move at a constant speed). (i.e. at least 154KW generator set)

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

A: P is good = 3/4*P rating (i.e. 0.75 times rated power).

14. Does the state stipulate that the engine power of a general generator set is much larger than that of a generator?

A: 10.

15. How to convert the engine power of some generator sets into kW?

A: 1 HP = 0.735 kW and 1 kW = 1.36 hp.

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

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

The simple formula is: I(A) = set rated power (KW) * 1.8

17. The relationship between apparent power, active power, rated power, large power and economic power?

A: 1) Considering the set of apparent power as KVA, China is used to express the capacity of transformers and UPS.

2) Active power is 0.8 times of apparent power in sets of KW. It is customary for power generation equipment and electric equipment in China.

3) The rated power of the diesel generator set is the power that can run continuously for 12 hours.

4) High power is 1.1 times the rated power, but only 1 hour is allowed for use within 12 hours.

5) Economic power is 0.75 times of rated power, which is the output power of diesel generator sets that can operate for a long time without time limitation. At this power, fuel economy and failure rate are low.

18. Why don’t diesel generator sets be allowed to operate for a long time under 50% of rated power?

A: Increased fuel consumption, easy coking of diesel engine, increased failure rate and shortened overhaul cycle.

19. Does the actual output power of the generator operate according to the power meter or the ammeter?

A: The ammeter is the reference only.

20. The frequency and voltage of a generator set are not stable. The problem is whether the engine or the generator?

A: It’s the engine.

21. Frequency stability of a generator set and voltage instability is the problem of engine or generator?

A: It’s the generator.

22. What happens to the loss of excitation of generator and how to deal with it?

A: The generator is not used for a long time, which results in the loss of residual magnet contained in the iron core before leaving the factory. The excitation cfuel can not establish the magnetic field it should have. At this time, the engine is running normally but can not generate electricity. This phenomenon is new. Or long-term non-use of more sets.

Processing method: 1) Push the excitation button once with excitation button, 2) Charge it with battery, 3) Take a bulb load and run over speed for several seconds.

23. After a period of time, the generator set finds that everything else is normal but the power decreases. What is the main reason?

A: 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 is too dirty and the amount of fuel injected is not enough. It must be replaced or cleaned. C. The ignition time is not correct and must be adjusted.

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

A: The problem is that the load of the customer is unstable and the quality of the generator is absolutely OK.

25. Frequency instability of a generator set. What are the main problems?

A: The main problem is the unstable speed of the generator.

26. What are the most important points that must be paid attention to in the use of diesel generator set?

A: 1) The water in the tank must be sufficient and operate within the allowable temperature range.

2) Lubricating fuel must be in place, but not excessively, and work within the allowable pressure range. 3) The frequency is stable at about 50HZ and the voltage is stable at about 400V. 4) Three-phase current is within rated range.

27. How many parts do diesel generator sets need to be replaced or cleaned frequently?

A: Diesel fuel filter, fuel filter, air filter. (individual sets also have water filters)

28. What are the main advantages of a brushless generator?

A: (1) Remove the maintenance of carbon brush; (2) Anti-radio interference; (3) Reduce the loss of excitation fault.

29. What is the general insulation level of domestic generators?

A: Domestic machine Class B; Marathon brand machines, Lillisenma brand machines and Stanford brand machines are Class H.

30. What gasoline engine fuel needs gasoline and fuel blending?

A: A two-stroke gasoline engine.

31. What are the conditions for the use of two generator sets in parallel? What device is used to complete and machine work?

A: The condition for parallel operation is that the instantaneous voltage, frequency and phase of the two machines are the same. Commonly known as “three simultaneous”. Use special machine-parallel device to complete machine-parallel work. Fully automatic cabinet is generally recommended. Try not to combine manually. Because success or failure of a manual merger depends on human experience. With more than 20 years experience in electric power work, the author boldly states that the reliable success rate of manual paralleling of diesel generators equals 0. Never use the concept of manual shunting to apply small power supply system to Municipal Radio and TV University power supply system, because the protection levels of the two systems are quite different.

32. What is the power factor of three-phase generator? Can a power compensator be added to improve the power factor?

A: The power factor is 0.8. No, because the charge and discharge of capacitors will cause small power fluctuations. And set oscillation.

33. Why do we ask our customers to tighten all electrical contacts after every 200 hours of set operation?

A: The diesel generator set is a vibration worker. And many sets sold or assembled domestically should use double nuts. The spring gasket is useless. Once the electrical fasteners are loose, a large contact resistance will occur, which will cause the set to run abnormally.

34. Why must the generator room be clean and free of floating sand?

A: If a diesel engine inhales dirty air, it will reduce its power. If the generator sucks in sand and other impurities, the insulation between stator and rotor gaps will be damaged, or even burned out.

35. Why has it not been generally recommended for users to use neutral grounding in installation since recent years?

A: 1) The self-regulation function of the new generation generator has been greatly enhanced;

2) It is found in practice that lightning failure rate of neutral grounding set is relatively high.

3) The requirement of grounding quality is high and can not be reached by common users. Unsafe working ground is better than ungrounded.

4) sets grounded at the neutral point have the opportsety to cover up leakage faults and grounding errors of loads which cannot be exposed under the condition of large current supply at municipal power stations.

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

A: Line 0 may be live because the capacitive voltage between the fire wire and the neutral point cannot be eliminated. Operators must view line 0 as live. Cannot be handled according to the market electricity habit.

37. How to match the power of UPS with diesel generator to ensure the stable output of UPS?

A: 1) UPS is generally represented by apparent power KVA, which is first multiplied by 0.8 and converted into set KW consistent with the active power of the generator.

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

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

38. Can the electronic or electrical components marked 500V withstand voltage be used in the diesel generator control cabinet?

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

39. Are all diesel generators equipped with self-protection?

A: No. There are some with and some without in the market today even in the same brand groups. When purchasing a set, the user must make it clear to himself. Very well written as an attachment to the contract. Generally, low-price machines do not have self-protection function.

40. What are the benefits of customers buying self-startup cabinets but not buying them?

A: 1) Once the power failure occurs in the city network, the set will start automatically to speed up the manual power transmission time;

2) If the lighting line is connected at the front of the air switch, it can also ensure that the lighting in the computer room is not affected by power failure, so as to facilitate the operation of the operators.

41. What does the general symbol GF for domestic generator sets mean?

A: Represents two meanings: a) Power frequency generator set is suitable for China’s general power 50HZ generator set. B) Domestic generator sets.

42. Does the load carried by the generator have to keep three-phase balance in use?

A: Yes. The large deviation must not exceed 25%. Phase missing operation is strictly prohibited.

43. What four strokes does a four-stroke diesel engine mean?

A: Inhalation, compression, work and exhaust.

44. What’s the big difference between a diesel engine and a gasoline engine?

A: 1) Pressure in cylinder is different. Diesel engines compress air during the compression stroke phase; A gasoline engine compresses a mixture of gasoline and air during the compression stroke phase.

2) Different ignition methods. Diesel engines spontaneously ignite by spraying atomized diesel fuel into high-pressure gases. Gasoline engines are ignited by spark plugs.

45. What does “two votes, three systems” mean in power system?

A: Two tickets refer to work ticket and operation ticket. Any work or operation performed on electrical equipment. The work and operation tickets issued by the person in charge on duty must be collected first. The parties must enforce by vote. Three systems refer to shift system, patrol inspection system and regular equipment switching system.

46. What is the so-called three-phase four-wire system?

A: There are 4 outgoing lines of the generator set, of which 3 are fire lines and 1 is zero line. The voltage between the lines is 380V. The distance between the fire line and the zero line is 220 V.

47. What about three-phase short circuit? What are the consequences?

A: Without any overload between the lines, a direct short circuit is a three-phase short circuit. The consequences are terrible, and serious consequences could lead to machine destruction and death.

48. What is the so-called back power supply? What are the two serious consequences?

A: Power supply from self-provided generator to city network is called reverse power supply. There are two serious consequences:a)

No power failure occurs in the city network, and the power supply of the city network and the power supply of the self-contained generator are not synchronized, which will destroy the sets. If the capacity of self-provided generator is large, the city network will also oscillate. B)

Municipal power grid has been cut off and is under maintenance. Its own generators supply power back. Will cause the power supply department maintenance personnel to electrocute and die.

49. Why must the debugger thoroughly check whether all the fixing bolts of the set are in good condition before debugging? Are all line interfaces intact?

A: After long-distance transportation, sometimes it is unavoidable for the set to loose or drop the bolts and line connections. The lighter the debugging, the heavier the damage to the machine.

50. What level of energy does electric energy belong to? What are the characteristics of AC?

A: Electrical energy belongs to secondary energy. AC is converted from mechanical energy and DC is converted from chemical energy. AC is characterized by its inability to store. It is now found for use.

51. What conditions can the generator meet before closing for power supply?

A: The water cooling set and water temperature reach 56 degrees Celsius. Air-cooled set and body are slightly hot. Voltage frequency is normal at no load. fuel pressure is normal. Only then can power be closed.

52. What is the sequence of loads after power-on?

A: Loads are carried from large to small.

53. What is the unloading sequence before shutdown?

A: Loads are unloaded from small to large and shut down afterwards.

54. Why can’t we turn off and on with load?

A: Shutdown with load is an emergency stop.

Post time: Aug-30-2019