Posted 14 Dec 2010 09:30
First, the structure and principle of a structure mainly by the synchronous generator stator, rotor and other components. Stator including stator ****, stator windings, frame; rotor section including the rotor ****, excitation winding and slip rings (there are sets of salient pole rotor hoop, heart ring, rotor have salient poles, the magnetic yoke, the rotor frame ); other parts, including brush devices, end caps, bearings and fans. 2, the working principle of Synchronous Generator is based on the principle of electromagnetic induction to work, it is through the rotor magnetic field and the relative movement of the stator windings, the mechanical energy into electrical energy. Driven by the external force when the rotor, rotor and stator magnetic field for the relative movement of the conductor, the conductor cutting magnetic field lines, the induced electromotive force generated in the conductor, and its direction can be determined under the right-hand rule. As the rotor magnetic pole position of the conductor cutting magnetic field lines in a vertical direction, so in this case the induced electromotive force in the stator windings the maximum. When the pole after turning 90 degrees. Pole into a horizontal position, the conductor without cutting magnetic line, the induced voltage is zero. Rotor sub-90 degrees, regular vertical cut Youyi stator magnetic field lines, the induced voltage reaches the maximum, but before the opposite direction. When the rotor sub-90 degrees, EMF and zero. This week, turning the rotor, stator winding induced voltage also occurred in the positive and negative changes. If the rotor continuous uniform rotation, in the stator windings to sense a changing periodically alternating electromotive force. Second, fault diagnosis and troubleshooting 1, generator heat (1) generator was not running the required technical conditions, such as the stator voltage is too high, the iron loss increases; load current is too large, the stator winding copper loss increases; frequency over low, so that the cooling fan speed slower for generating heat; power factor is too low, the rotor excitation current increases, causing the rotor heat. Monitoring Instrument should check the instructions correctly. If not normal, to make the necessary adjustment and processing, the generator is running in accordance with the provisions of the technical conditions. (2) three-phase generator unbalanced load current, overload of one phase winding will overheat; if the difference between three-phase current exceeds 10% of rated current, which is a serious mantis phase current imbalance, phase current imbalance will produce negative sequence magnetic field, thereby increasing the losses caused by magnetic winding and other parts of Hooping fever. Three-phase load should be adjusted so as to maintain the phase current balance. (3) dust duct is blocked, poor ventilation, resulting in difficulties in generating heat. Should clear the air duct dust, grease, the duct open. (4) inlet air temperature is too high or water temperature is too high, cooler with clogging. Should be lowered into the cooler air or water temperature within the obstruction clearance. The fault is not excluded, should limit the load generator to reduce generator temperature. (5) bearing grease too much or too little grease should be required, usually bearing room 1 / 2 to 1 / 3 (low speed to take the ceiling to take the high speed limit) and no more than bearing room 70% is appropriate. (6) bearing wear. If the wear is not serious, so that local overheating bearings; if badly worn, it is possible to make the stator and rotor friction, causing the Ministry to avoid overheating of the stator and rotor. Bearings should be checked whether the noise, stator and rotor friction if found, immediately shut down for repair or replacement. (7) The stator **** insulation damage, lead to short circuit chip, the local **** eddy current loss caused by the increase of fever, causes severe damage to the stator windings. Should be immediately shut down for repairs. (8) of the stator windings in parallel wire break, so that the current increase of the other hot wire. Should be immediately shut down for repairs. 2, the generator neutral to ground voltage is abnormal (1) Under normal circumstances, due to the high harmonics, or manufacturing processes and other causes uneven air gap under the pole, the magnetic potential of the emergence of low-voltage range If the voltage in one to several volts, no danger, having to deal with. (2) the generator windings to ground short circuit or poor insulation, the use of performance deterioration of electrical equipment and generators, easy to heat, it is timely maintenance to prevent spreading of the accident. (3) no-load no-voltage neutral to ground, while the voltage when the load is due to phase unbalance caused by three-phase load should be adjusted so that the basic balance. 3, the generator over-current (1) the load is too large, should alleviate the load. (2) transmission line phase short circuit or ground fault, response lines for maintenance, troubleshooting can be back to normal. 4, the generator terminal voltage is too high (1) power generator in parallel with the grid voltage is too high, should lower the voltage of the generator in parallel. (2) excitation device failure caused by over-excitation, excitation system should be timely maintenance. 5, lack of **** excitation device as inadequate compensation voltage source compounding can not provide the required excitation current armature reaction, the generator terminal voltage is lower than the grid voltage, send not rated ****, should take the following measures: (1) excitation in the generator and the reactor of a three-phase between the access regulator, to improve the generator terminal voltage, so that the magnetic excitation potential of the device increases. (2) changing the excitation system voltage flux potential and the generator terminal voltage, phase, so the potential synthesis of the total flux increases in the reactor in parallel across each winding of thousands of European, 10W resistor. (3) reduce the resistance of rheostat, so that the excitation current increases. 6, stator winding insulation breakdown, short circuit (1) damp the stator windings. For a long time, long-term disabled or maintenance of the generator, put into operation before measurement of insulation resistance, were not allowed to fail in operation. Generators to conduct drying damp. (2) The process of winding itself is defective or improper maintenance, resulting in winding insulation breakdown or mechanical damage. Insulation level should be required to select insulation materials with embedded winding and dipping and drying process to be strictly in accordance with the requirements. (3) winding overheating. After the insulation thermal insulation will reduce, and sometimes very quickly at high temperatures caused by insulation breakdown. Check daily inspections should be strengthened to prevent the generator to overheat and damage the part of the winding insulation. (4) insulation aging. General generator running 15 to 20 years, the winding insulation aging, changes in electrical properties, and even the insulation breakdown. To make the generator preventive maintenance and testing, if found to insulation failure, it is timely replacement of the defective winding winding insulation or replacement to extend the life of the generator. (5) into the metallic foreign body in the internal generator, generator repair, after the metal objects should not be, parts or tools left behind in the stator bore; tied rotor banding line, fastening end parts, so as not to occur as a result of centrifugal force and loose. (6) over-voltage breakdown: 1) line being struck by lightning, and lightning protection is imperfect. Lightning protection facilities should be improved. 2) misuse, such as no-load, the generator voltage rise too high. Should strictly follow the rules of the generator step-up to prevent misuse. 3) The internal over-voltage generator, including operating over-voltage, over voltage and resonant grounding arc over voltage, winding insulation should be strengthened preventive test, to detect and eliminate in the stator winding insulation defects. 7, the stator **** relaxation due to improper assembly manufacturing, the **** does not fasten well. If it is the **** relaxation, for small generators, used two less than the diameter of the stator end winding iron, wear studs, tighten the ****. After the prototype to be restored, and then tighten the clamping bolt for the original ****. If the locality of **** relaxation, can be painted in the relaxation between the silicon chip paint, and then in the relaxation part of the insulating material can be hard to break into. 8 iron chip short circuit (1) **** lamination relaxation, when the generator running vibration and damage insulation ****; iron chip in some places damaged insulation or **** local overheating, the insulation aging, according to the original plan to article Methods for processing. (2) iron edge burrs or chips by mechanical damage during maintenance. Application of fine rasp to remove burrs, damage repair place, clean the surface, then coated with a layer of silicon paint. (3) short the solder or copper **** tablets should be shaving or cutting of metal weld joints in addition, to handle the surface. (4) short-circuit winding arc occurs, it may cause short-circuit ****, burning part of the chisel should be removed, the handle surface. 9, generator loss of residual magnetism, electricity can not start (1) often lose remanence after the shutdown is due to the exciter pole close to the soft materials used in steel, low residual magnetism. When there is no downtime after the current field winding magnetic field disappears, the battery should be available in power before the magnetization. (2) loss of magnetic pole generator should pass into the winding rated current larger than the DC current (very short) to charge and magnetic remanence that is able to recover enough. 10, automatic excitation device excitation temperature reactor (1) local short-circuit reactance coil, reactor should overhaul. (2) choke the air gap magnetic circuit is too large, adjust the magnetic gap. 11, the generator starts, the voltage does not rise up (1) excitation circuit disconnection, the voltage does not rise up. Excitation circuit should be checked whether the break, the contact is good. (2) remanence disappears, if the exciter voltage meter shows residual magnetism disappears without instructions, response exciter magnetizing. (3) the exciter coil magnetic field reversed polarity, it should be positive, negative cable on the exchange. (4) to do some maintenance in the generator test mistake to reverse direct current through the coil magnetic field, resulting in residual magnetism disappear or reverse, should be re-magnetized. 12, out of step oscillation generator under normal circumstances, the generator and load power is given the power equilibrium of. When a short circuit failure or a significant generator load rejection, the generator power to the user's load is not balanced. To adjust the load to balance, because the rotor inertia and governor delay a process, during this period, stable operation of the generator is destroyed, the generator oscillation. If the story seriously, and even make out of sync with the system generator. Step oscillation generator, the duty should be created by increasing the excitation current to restore the conditions for synchronization; it may be appropriate to adjust the machine's load, to help restore synchronization. 13, vibration generator (1) The rotor is not round or balance is not adjusted, should be strictly manufacture and installation of quality or re-adjust the balance of the rotor. (2) shaft bending, can be grinding, heating and hammering law correction shaft. (3) coupling connection is not correct, should be re-high-speed coupling with the bolt clamping force, if necessary, be re-coupling face processing. (4) structural components of the resonance, by changing the structural components of the support methods to change its natural frequency. (5) layer excitation winding short circuit, should overhaul the field winding, and be insulated. (6) or hydraulic oil supply shortage, the nozzle diameter should be increased to increase oil; reduce the gap to increase oil supply port. (7) excessive or hydraulic oil is too high to reduce the nozzle diameter, lower oil pressure, increased area of pressure, increasing the gap. (8) The stator **** assembly loose, should be re-pressed and ****. (9) bearing seal tight, so that local overheating of the shaft, bending. Bearing seals should be checked and adjusted to match the right axis with the gap. (10) asymmetric generator ventilation system, should pay attention to both ends of the stator **** and rotor wind deflector wind deflector support the choice of structural arrangement and size of the wind path system symmetry, enhanced cover, wind shield of the stiffness and tight solid-solid.