The insulation breakdown accident often occurred in generator. It includes interphases short circuit, inter-turn short circuit and ground fault.
The interphase short circuit: the generator windings ends will be greatly impacted by electric power and may make the coil end deformed under two-phase or three-phase short circuit and differential protection tripping happening.
Inter-turn short circuit: Generator outlet blasting, if it continues a long time, the stator copper wire will be melted. When no-load run, the generator three-phase voltage will be imbalance.
Ground fault: Generator breakdown location is in the linear portion or notch position and stator ground protection act. The insulation resistance value between stator ground and ground is zero or minimum.
The fundamental reason of generator insulation breakdown is that the stator coil insulation is weak or there is a corona etching in notch in run time. The treatment method is to find the point of breakdown and reworked and reinforced insulation. At the same time, eliminating the corona etching in a maximum extent is important.
III. A large noise or vibration with generator
The reasons of a large noise or vibration with generator are:
1. Foundation bolts loose, or STG subsidence. Treatment: fastening bolts. Recalibration concentricity.
2. Generator rotor and Steam Turbine shaft are misalignment. Treatment: calibration concentricity.
3. Bearing wall worn or damaged under short oil. Treatment: repaired bearing or replace a new bearing with same model.
4. There is a friction between the stator and rotor. Treatment: find the friction location and reason, and then eliminate it.
5. Fan or other fasteners loose. Treatment: Tighten fan and fasteners.
6. Rotor coil partial short circuit, two points grounding or wiring errors. Treatment: please inspect the insulation of slip ring and the rotor coil to the ground. Or connect to the DC power source and check the voltage drop of each coil, winding direction and wiring method. So we can identify the cause of the malfunction and eliminate them.
7. Brush is too hard, or the pressure is too large. Treatment: adjust the pressure or replace the same type of brush.
8. Three-phase current are severe asymmetry. Treatment: please investigate that the three-phase current imbalance is in the allowable range or not. If it is not in the allowable range, please adjust three-phase load or reduce the load.
9. Stator winding short circuit or ground. Treatment: Find out the fault and repair it.
10. External fault or lightning strike. Treatment: if the vibration time is too long, please stop the STG and inspect.
Typical
cases:
This is a 15 MW generator from a Shandong customer. The vibration of generator is reached to 0.12mm in running. After inspection the generator, we found that rotor dynamic AC impedance upheaval 12% in 2400-2700 and the dynamic inter-turn short circuit is serious. It destroys the balance of the magnetic field and causes the electromagnetic force uneven of generator rotor. After removal of the rotor retaining ring and treatment the rotor inter-turns, we start the STG. The vibration is about 0.01mm.
IV. The temperature of a generator is too high.
Generally the temperature of a generator will be in the allowable value, if the generator running normally and the current, voltage, frequency, power, excitation current and power factor are all within the allowable fluctuation range. If a generator stator, core and other parts temperature are too high, please consider the following cases:
1. Generator overload operation and exceed the allowable time. Treatment: Please reduce the generator load to the rated load or under rated load as soon as possible.
2. Three-phase current are serious imbalance. Treatment: please find out the reason of imbalance. If it is the voltage causing, please check if it is the generator inter-turn short circuit. If it is load causing, please adjust the load and make it balance.
3. The ventilation cooling system of generator is poor. For example, the temperature is too high, the air duct or exhaust duct are blocked, the coil and its ends are serious fouling. Treatment: please reduce the load suitability, improve ventilation, and remove fouling.
4. The stator winding portion short circuit or ground. Treatment: Find out the short circuit or ground point and repair them, and then eliminate short circuit or ground risks.
5. Insulation of the stator core may be partially damaged and short circuit, so there is a vortex and overheat. Treatment: please reduce the load suitability. If the generator reduces its efficiency obviously, please repair the generator stator core.
6. The bearing is short of lubricating oil. The oil number is wrong. The oil quality is bad. The bearing is installed with a wrong way or the bearing is damaged. Treatment: please find out the reason and then replace the oil or clean, adjust or replace bearing.
V. Generator rotor ground
Symptom: Generator grounding one point or two points grounding light plate light.
Fault Analysis: Generator rotor winding insulation damage, coil deformity and severe dust and greasy attached in the ends seriously are all leading to the grounding of the generator rotor windings. When the generator rotor winding grounding in one point, there is electrical current pass as the ground does not constitute an electrical circuit.
However, after one point grounded, it is easy of leading another grounding point. If any part in excitation circuit ground, it can form ground fault of two or more points ground. It is very dangerous.
After the failure, the rotor windings are short-circuited. Because of the small winding DC resistance, the excitation current will increase. So the magnetic field of generator is out of balance, and main magnetic flux reduces largely. So the STG will vibrant strongly. Meanwhile the power factor of the generator will be increased significantly and get into leading phase running (absorption of reactive power from the grid).
The stator field becomes in the frond and the rotor field becomes in the back. It will make the stator current increases. If the watcher notice that there is no excitation varying but the excitation current and stator current suddenly increases, and the excitation voltage and AC voltage are all suddenly drop, and power factor meter indicates increasing or leading phase, it means the generator rotor grounded or inter-turn short circuited. You should shut down the STG and blow-out magnetic. Please inspect the excitation system and rotor windings, and find out the short circuit point and treat it.
VI. Excitation upgrading and generator test
Excitation system upgrading, brushless exciter changes into the SCR excitation and make the generator maintenance easily. And it removes the disadvantage of brushless excitation dynamic adjustment slowly. The generator test includes stator insulation resistance test, the absorption ratio test, the iron loss test, leak test, AC and DC voltage withstand test, the rotor high speed balancing and overspeed test, dynamic and static AC impedance test, the generator no-load test, short circuit test, temperature rise test, residual pressure measurement, axis voltage measurement.
Generator Care,Steam Turbine Generator Care,Msw Power Generation,Combined Cycle Generating Unit Shandong Qingneng Power Co., Ltd. , https://www.steamturbine.be
The motor is high-power, the base is increased.
Both the body and base use high quality cast iron, strong and everlasting.
The handle can match for special switch, safety and reliable.
There are wheels on base which can moving easily, and using bolts fasten the base enable working more reliable.
Using high quality fiber strengthen grinding flat, safety and reliable.
SPECIFICATIONS:
MODEL
G2210×40B
G2210 × 40A
G2210×40C
Motor
Power (KW)
2.2
2.2
3.0
Â
Voltage (V)
220-240
220-240
220-240
Â
Â
380-415
380-415
380-415
Textile fiber enhancement  grinding wheel piece
Specifications
400×3.2×32
(25.4)400 x 3.2 x 32
(25.4)400×3.2×32
(25.4)
Â
Rated linear velocity
(m/s)70
70
70
Spindle speed (R . P . M)
2100
2800
2100
Angle range of jaws(°)
0-±45
0-±45
0-±45
Cut-off capability
Steel pipe(mm)
Φ100×6
Φ100×6
Φ100×6
Â
Angle steel(mm)
100×10
100×10
100×10
Â
Channel steel(mm)
100×48
100×48
100×48
Â
Columnar steel(mm)
Φ50
Φ50
Φ50
N.G./G.W.(kg)
74/80
68/76
79/85
Packing dimensions(cm)
730×460×580
730×460×560
840×460×
580
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Contact Us: Â
Andy WangÂ
TENGZHOU HOTON MACHINERY CO.,LTD
Tel:0086 632 5633796
MP:0086 13506328892
www.hotonmachinery.com
 Company Profile:     Â
    Tengzhou Hoton Machinery Co.,LTD was established in 2006, and is the professional machine manufacturer in China. There are 480 workers, of whom 60 are engineers. It has an area of 46,000 square meter, general assets 30,000,000. It has a store of 350 equipments and the good ability of products design & manufacturing. It has export quality permit from 2007, and has export right given by the State Foreign Economic Trade Committee in 2008.     The leading products: "Hoton" series of CNC machines, Lathes, Milling machines, Drilling machines,Grinding machines, Saws, Sheet metal machines, Metal forming machines, and other machine accessories.Some products have national patent.It has fourteen series, over eighty models by itself. It has the ability of making 100,000 sets every year. All the products are designed perfectly and has high quality high performance and low price, and the excellent quality guarantee system. The products have past ISO9001 and CE certification since 2009. The products have been export to five continents, over forty countries and areas. It resulted to the attraction of client abroad and home, the quickly promotion of products sale.    Tengzhou Hoton Machinery Co.,Ltd. is willing to make common progress and developments with all the customers.
Quality first,Constantly perfecting skills. Â
Model NO.: G2210x40C G2210x40B
Precision: Normal Precision
Certification: CE, ISO 9001
Condition: New
Voltage: As Customer Request
Color: As Customer Request
Motor: 2.2KW
weight: 80kgs
Angle angle of jaws: 45 degree
Trademark: HOTON
Transport Package: Plywood Case
Specification: 80kgs
Origin: China
HS Code: 8460190000
CUT OFF SAW MACHINE FEATURES: