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 parallel cabinets. Try not to manually parallelize. Because the success or failure of manual parallelization depends on human experience. With more than 20 years of experience in electric power work, the author boldly asserts that the reliable success rate of manual paralleling of diesel generators is equal to 0. Never apply the concept of manual paralleling of the large mains power supply system to the 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 fluctuations in the small power supply. and vibration of the unit.
3. Why do we require the customer to carry out a tightening of all electrical contacts after every 200 hours of operation of the unit? Answer: Diesel generator sets are vibration workers. Moreover, many domestically produced or assembled units are useless to use double nuts. The spring washer is useless. Once the electrical fasteners are loosened, a large contact resistance will be generated, resulting in abnormal operation of the unit.
4. Why must the generator room be clean and free of floating sand on the ground?
Answer: If the diesel engine inhales dirty air, the power will decrease; if the generator inhales impurities such as sand particles, the insulation between the stator and rotor gaps will be damaged, and in severe cases, it will be burned.
5. Why since 2002, our company generally does not recommend users to use neutral grounding during installation?
Answer: 1) The self-regulating function of the new generation generator is greatly enhanced; 2) In practice, it is found that the lightning failure rate of the neutral point grounding unit is relatively high; 3) The grounding quality requirements are relatively high, which cannot be achieved by ordinary users. Unsafe work grounding is worse than ungrounded; 4) The unit with neutral point grounded will cover the leakage faults and grounding errors of the load, and these faults and errors cannot be exposed under the condition of high-current power supply of mains.
6. What problems should be paid attention to when using the unit that is not grounded at the neutral point?
Answer: The 0 wire may be charged because the capacitive voltage between the live wire and the neutral point cannot be eliminated. The operator must regard the 0 line as a charged body. It cannot be dealt with according to the habit of commercial electricity.
7. How to match the power of the UPS and the diesel generator to ensure the stable output of the UPS?
Answer: 1) UPS is generally expressed by the apparent power KVA, first multiply it by 0.8 and convert it into a unit KW 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 the With generator power, that is, the generator power is twice the UPS power. 3) If a generator with PMG (permanent magnet machine excitation) is used, multiply the power of the UPS 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 the electronic or electrical components marked with a withstand voltage of 500V be used in the control cabinet of diesel generators?
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. Are all diesel generator sets equipped with self-protection function?
Answer: No. At present, some units of the same brand in the market have or not. Users have to figure it out for themselves when purchasing a unit. **Written in writing as an attachment to the contract. Generally, low-cost machines do not have self-protection functions.
10. How to identify fake and inferior domestic diesel engines?
Answer: First check whether there is a factory certificate and product certificate. They are the "identity certificate" of the diesel engine when it leaves the factory, and they are necessary. Check the three major numbers on the certificate again: 1) nameplate number; 2) body number (generally on the plane machined at the flywheel end, and the font is convex); 3) oil pump nameplate number. Check these three major numbers with the actual numbers on the diesel engine, and they must be accurate. If any doubts are found, these three serial numbers can be reported to the manufacturer for verification.
11. After the electrician takes over the diesel generator set, which three points should be verified first?
Answer: 1) Verify the real useful power of the unit. Then determine the economic power, and reserve power. The method for verifying the real useful power of the unit is: multiply the rated power of the diesel engine for 12 hours 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 used 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 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 be equipped?
Answer: 22*7=154KW (the elevator is a direct start-up model with load, and the instantaneous starting current is generally 7 times the rated current to ensure the elevator moves at a uniform speed). (that is, at least a 154KW generator set should be equipped)
13. How to calculate the maximum use power (economic power) of the generator set?
Answer: P**=3/4*P rated (ie 0.75 times rated power).
14. The state stipulates that the engine power of the general generator set should be larger than the generator power?
Answer: 10℅.
15. The engine power of some generator sets is expressed in horsepower. How to convert the horsepower to the international unit kilowatt?
Answer: 1 horsepower = 0.735 kilowatts, 1 kilowatt = 1.36 horsepower.
16. How to calculate the current of the three-phase generator?
Answer: I=P/(√3 Ucos φ), that is, current = power (W)/(√3 *400(V)*0.8) The simplified formula is: I (A) = rated power of the unit (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 my country; 2) The active power is 0.8 times the apparent power, and the unit is KW, which is used for power generation equipment and electrical equipment in my country; 3) The rated power of the diesel generator set refers to the power that can run continuously for 12 hours; 4) The maximum power is 1.1 times the rated power, but only 1 hour of use is allowed within 12 hours; 5) The economic power is 0.75 times the rated power , is the output power of diesel generator set that can run for a long time without time limit. When running at this power, the fuel is the most economical and the failure rate is the highest.
18. Why is the diesel generator set not allowed to run for a long time below 50% of the rated power?
A: The oil consumption is increased, the diesel engine is easy to carbonize, the failure rate is increased, and the overhaul period is shortened.
19. Is the actual output power of the generator in operation based on the power meter or the ammeter?
Answer: The ammeter shall prevail, the power meter is only for reference
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