In the investigation of the use of diesel generators, the analysis and research on the failure of the excitation of some diesel generators from 75kW to 200kW appeared. The full load operation time is too long, the load function device often fails, and the diesel generator has no voltage after inspection, and the factor of the burnt rate is low. , Three or more high-order harmonics are serious, three-phase load smell, open the diesel generator to find that the excitation windings have been burned, the disassembly and inspection are severely unbalanced, frequently start high-power asynchronous motors, and the excitation is found to be controllable. Both the silicon and the freewheeling diode have been broken down and damaged. Diesel generators and loads are short-circuited, safety devices are malfunctioning or imperfect, and in view of the universality of such failures, continuous operation in a high temperature and high humidity environment causes changes in the state of excessive temperature rise of diesel generators. Therefore, what control measures should be paid attention to during the use of diesel generators:
(1) Strictly control the temperature rise of diesel generators (based on the temperature of 40°C) not to exceed 50°C. During operation, it is often detected by touch and thermometer. When the temperature of the outer ring of the bearing exceeds 95°C, the grease is diluted out, or the bearing is rustling, the machine should be shut down immediately to find out the cause, and the operation can be performed after troubleshooting .
(2) Keep the governor in good condition, stabilize the diesel generator speed at 1500r/min, and make the cycle reach 50Hz. If the cycle changes during operation, adjust the stable cycle of the diesel engine throttle in time and check whether the governor is operating normally.
(3) Change the lubricating grease as needed during the secondary maintenance of the diesel generator. The amount of lubricating grease should be about 1/2 to 2/3 of the bearing gap. The bearing should be carefully inspected according to the instruction manual. If the ball or the inner and outer rings of the bearing appear blue-purple, it means that the bearing has been heated and annealed and should be used or replaced. When replacing the bearing, the fit between the inner and outer holes of the bearing and the shaft and body should meet the specified interference. If it is too loose, tin the inner and outer rings of the bearing and assemble it after fine grinding; when it is too tight, it should be assembled after careful sanding with No. 00 sandpaper to prevent If the bearing fit is too loose, slipping, friction and heat generation, it also prevents the bearing clearance from being reduced when the bearing is too tight, increasing wear, and increasing temperature rise.
(4) When using diesel generators, electric equipment should be used as far as possible to allocate reasonably, and the three-phase power should be balanced (the A phase of the rectifier excitation has consumed 2kW of power), and the three-phase unbalance should not exceed 20%. Try to use a three-phase electric welding machine. When using a two-phase welding machine, stop other equipment and intermittent butt welding. Pay close attention to the body temperature during work. If the temperature rises too high, shut down the machine immediately to cool down.
(5) Cooling and dehumidification measures should be taken for diesel generators operating in high temperature and high humidity environments, such as the use of blowers to improve ventilation conditions, intermittent operation to cool them, and control the body temperature not to exceed 90°C, or reduce the load not to exceed diesel power generation 85% of the engine capacity, the top of the diesel generator is sealed to prevent rain.
(6) In principle, it is forbidden to use diesel generators with overload. In special circumstances, such as when using diesel generators for butt welding of steel bars, intermittent operations should be performed and the temperature rise of diesel generators should be strictly controlled. Once the temperature rise is too high, immediately It is cooled by a blower when it is stopped, and put into use after cooling down. The maximum capacity of the load motor should not exceed 40% of the generator capacity, and the interval between intermittent starting of the motor should not be less than 1 min, try to avoid frequent starting.
(7) The excitation current should be closely observed during the operation of the diesel genset, and the load should be reduced if it exceeds the rated value. If the adjustment has no effect, check whether the excitation winding is seriously leaked or short-circuited due to insulation degradation (the cold state of the diesel generator is less than 2MΩ, and the thermal stability is less than 0.5MΩ). Do not force the operation to avoid damage to the machine.
(8) If the diesel generator is not used for a long time, the stator should be dried by the steady-state short-circuit current method to dissipate moisture before use. It can be used only after the insulation is greater than 2MΩ.
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