1. What are the conditions for the parallel use of two generator sets? What device is used to complete the parallel work?
Answer: The condition for parallel use is that the instantaneous voltage, frequency and phase of the two machines are the same. Commonly known as “three simultaneous”. Use a dedicated parallel device to complete the parallel work. It is generally recommended to use fully automatic cabinets. Try not to use manual paralleling. Because the success or failure of manual paralleling depends on human experience. With more than 20 years of experience in electric power work, the author boldly stated that the reliable success rate of manual parallel diesel generators is equal to zero. Never use the concept of manual paralleling for a large mains power supply system to apply a small power supply system, because the protection levels of the two are completely different.
2. What is the power factor of the three-phase generator? Can a power compensator be added to improve the power factor?
Answer: The power factor is 0.8. No, because the charging and discharging of the capacitor will cause the fluctuation of the small power supply. And the unit oscillates.
3. Why do we require customers to tighten all electrical contacts every 200 hours of operation? Answer: Diesel generator set is a vibrating working device. Moreover, many domestically produced or assembled units should use double nuts which are useless. The use of spring washers is useless. Once the electrical fasteners are loosened, a large contact resistance will be generated, which will cause the unit to operate abnormally.
4. Why must the generator room be clean and free of floating sand on the ground?
Answer: If the diesel engine sucks in dirty air, the power will decrease; if the generator sucks in sand and other impurities, the insulation between the stator and rotor gaps will be damaged, and the worst will cause burnout.
5. Since 2002, why our company generally does not recommend users to use neutral point grounding during installation?
Answer: 1) The self-adjustment function of the new generation of generators is greatly enhanced; 2) In practice, it is found that the lightning failure rate of the neutral grounding unit is relatively high; 3) The grounding quality requirements are high, and ordinary users cannot do it. Unsafe working grounding is not as good as not grounding; 4) The neutral grounded unit will cover up the load leakage faults and grounding errors, and these faults and errors cannot be exposed under the condition of large current power supply from the mains.
6. What problems should be paid attention to when using the neutral point ungrounded unit?
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?
Answer: 1) UPS is generally expressed by apparent power KVA, first multiply it by 0.8 to convert it to the unit KW consistent with the generator active power; 2) If a general generator is used, the UPS active power is multiplied by 2 to determine the 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 power of the UPS is multiplied by 1.2 to determine the power of the generator, that is, the power of the generator is 1.2 times the power of the UPS
. 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 (generally on the plane machined at the flywheel end, the font is convex); 3) 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?
Answer: 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, the data must be used as the real useful power of the unit; 2) Verify which types of self-protection functions the unit has; 3) Verify whether the power wiring of the unit is qualified and whether the protective grounding is reliable. Whether the 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.
16. How to calculate the current of a three-phase generator?
Answer: I=P/(√3 Ucos φ), that is, current=power (watt)/(√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?
Answer: 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 of apparent power, and the unit is KW. Our 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, It is the output power that the diesel generator set can run for a long time without time limit. 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.
Post time: Oct-26-2021