Synchronous generator is one of the most commonly used alternators and is an indispensable part of diesel generator set. In the modern power industry, it is widely used in hydropower generation, thermal power generation, nuclear power generation and diesel power generation. The major end period of synchronous generator is generally 2 to 4 years, and the main overhaul contents are as follows:
1、 Probe the body and take out the rotor.
(1) Mark the screws, pins, gaskets, cable heads, etc. before disassembly. The cable head shall be wrapped with clean cloth after disassembly, and the rotor slip ring shall be coated with neutral vaseline and wrapped with highland barley paper.
(2) After removing the end cover, carefully check the air gap between the rotor and the stator, and measure the upper, lower, left and right clearances.
(3) When taking out the rotor, it is not allowed to collide or rub with the stator. After taking out the rotor, it should be placed on a stable hardwood pad.
2、 Repair the stator.
(1) Check the base and shell and clean them. The paint is required to be intact.
(2) Check the inside of the stator core, winding and base, and clean the dust, oil dirt and sundries. The dirt on the winding can only be removed with a wooden or plastic shovel and wiped with a clean rag. Be careful not to damage the insulation.
(3) Check whether the connection between the stator shell and the iron core is tight and whether there are cracks at the welding position.
(4) Check the integrity of the stator and its parts, and complete the missing parts.
(5) Use a 1000-2500V megger to measure the insulation resistance of three-phase winding. If the resistance value is unqualified, find out the cause and take corresponding measures.
(6) Check the silicon steel sheet of stator core for rust, looseness and damage. If there are rust spots. The silicon steel sheet paint can be applied after the metal brush is removed. If there is looseness, a wedge made of thin mica sheet or epoxy glass plywood can be driven. In case of discoloration and rust caused by local overheating, iron core test shall be conducted. When the iron loss and temperature rise are unqualified, special treatment shall be carried out for the iron core.
(7) Check whether the stator slot wedge is loose, broken and protruding, and check whether the bar in the ventilation ditch is bulging. If the wedge and insulating sleeve are blackened, it indicates overheating. Poor ventilation should be eliminated or the load should be reduced. Check the end insulation for damage. When the insulation cushion block and insulation clamp are dry, they can be padded or replaced. If the end binding is loose, the old binding wire can be removed and re-bound with the new binding wire.
(8) Check whether the clamping screw of the stator core is loose. If the insulation pad under the clamping nut is damaged, replace it. Use a 500-1000V megger to measure the insulation resistance of the clamping screw, which should generally be 10-20M Ω.
(9) Check the tightness of the connection between the generator lead and the cable.
(10) Check whether the bearing splashes oil towards the end of the winding. If there is oil dirt on the end of the winding, wipe it with a clean cloth soaked in gasoline or carbon tetrachloride. If the end insulation is seriously corroded by oil, a layer of oil-resistant protective paint can be sprayed if necessary.
(11) Check and trim the felt pad on the end cover, sight glass, stator housing and other joints.
3、 Repair the rotor.
(1) Use a 500V megger to measure the insulation resistance of the rotor winding. If the resistance value is unqualified, find out the cause and deal with it.
(2) Check the surface of the generator rotor for discoloration and rust. If yes, it indicates that there is local overheating on the iron core, wedge or retaining ring, and the cause shall be found out and handled. If it cannot be eliminated, the generator output power shall be limited.
(3) Check the balance weight on the rotor. It should be fixed firmly without increase, decrease or displacement. The balance screw should be locked firmly.
(4) For the hidden pole rotor, check whether the slot wedge is loose, broken and discolored, check whether the collar and core ring are cracked, rusted and discolored, and check whether the joint between the collar and the rotor is loose and displaced.
(5) For salient-pole rotor, check whether the magnetic pole is rusty, whether the screw is tight, whether the magnetic pole winding is loose, and measure the insulation resistance of the winding, which should be qualified.
(6) Check the fan and remove dust and grease. The fan blades shall be free from looseness and fracture, and the locking screws shall be fastened.
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