This paper focuses on the situation of the stator magnet core magnetization test provided by GE Canada, and puts forward its own viewpoints based on domestic experience. It can be seen that domestic technology is superior to foreign countries.

Stator core; magnetization test; test standard 1 overview Liujiaxia Hydropower Plant No. 5 generator set is the first 30CMW stator and rotor dual-water inner-cooled water turbine generator set designed, manufactured and installed in China. It was put into operation on June 28, 1973. The safe operation has made tremendous contributions to the national electric power industry for 28 years, and has accumulated rich experience in the design, manufacture and operation of the dual-water internal cold water turbine generator set. Yellow sand sediment erosion, unit aging, especially generator insulation aging, turbine cavitation wear, has a certain impact on the safe operation of the unit. Therefore, the unit was replaced and transformed, and a 320MW hydroelectric generating unit was introduced from GE Canada. The stator core is stacked in the pit according to the national standard and GE's generator installation specification. The stator core stacking quality is checked by the stator core magnetization test. The generator stator base is welded and installed in the GE manufacturing plant, and then transported to the construction and installation site in 4 pieces, and stacked in the pit.

2 Generator and stator related parameters 21 Generator basic electrical parameters Generator model: API rated capacity: 320MW rated voltage: 18kV rated current: 11707A rated power factor: 0.9 (hysteresis) rated frequency: 50Hz stator connection: 4Y 2.2 power generation Machine stator core geometry and test related parameters stator core outer diameter: D1=12395mm stator core inner diameter: D2=11557mm stator core total height: L1=2131.06mm stator core tooth height: HC=146.41mm stator core ventilation groove number: n =54 stator core ventilation groove width: b = 4mm stator core lamination coefficient: K = 0.95 stator core yoke total weight: G = 148159kg stator core effective length: L = 1819. 3mm stator core yoke height: H = 272.59 stator Cross-sectional area of ​​core yoke: S=495923mm2 Average diameter of stator core yoke: Dav=121224mm Stator core allowable temperature rise: 25K core material Magnetic permeability: M17 silicon-aluminum-iron alloy, =4 3 stator core magnetization test 1 Test purpose generator stator core It is made up of silicon steel sheets. Due to the poor quality of the manufacturing and installation, or the operation, the insulation between the sheets is damaged due to the action of heat and mechanical force. Therefore, when the generator is installed and handed over, it is necessary to perform a magnetization test on the stator core to measure the loss of the core weight of the iron core, measure the temperature of the core yoke portion and the tooth portion, and check whether the temperature rise of each part exceeds a prescribed value, thereby comprehensively judging the core piece. Is the insulation good?

3.2 Test principle A special excitation coil is evenly wound in the circumferential direction of the stator core, and a power frequency alternating current is introduced to generate an alternating magnetic flux of about 1.0 T inside the stator core. Then, the stator core and the stator base generate eddy current and hysteresis loss, so that the stator core generates heat and the temperature rises. The stator core loss is measured by a wattmeter connected to the measuring coil, and the temperature and temperature rise of each part in the stator core are synchronously measured by a thermal imager, a pre-embedded thermometer and a pre-embedded thermocouple, and the measurement results are compared with prescribed standards. To determine the maximum temperature rise of the stator core teeth, the maximum temperature difference of the stator core teeth, whether the stator core unit loss exceeds the standard, whether the stator core has local overheating problems, and further determine the generator stator core stacking quality.

3.3 Test Standards Based on the National Technical Standard GB8564-88 Hydrogenerator Installation Technical Specification and the Liujiaxia Hydropower Plant No. 5 Generator Installation Manual compiled by GE, the following standards were developed.

Stator core unit iron loss (magnetic flux density 1.0T) - actual measured sub-core total loss, W; total weight of stator core yoke, kg; actual magnetic flux density, T. Standard: GE provides core material M17 silicon-aluminum-iron alloy unit iron Loss in (2) Stator core tooth maximum temperature rise (magnetic flux density 1.0T) - the highest core tooth temperature, core initial temperature, c; actual magnetic flux density, T. Standard: (3) stator core tooth maximum temperature difference (flux Density 1.0T) The maximum temperature of a core tooth, the lowest temperature of c-core tooth, the actual magnetic flux density of c, T. Standard: Test magnetic flux density 1.0T, test duration 90min When the local temperature of the stator core exceeds the average temperature of the stator core by more than 10C It is considered that the part has overheating.

(6) When the average temperature of the stator core exceeds the temperature of the stator base by more than 10C, the core magnetization test should be stopped immediately to prevent damage to the stator core and the stator frame.

4 test method 1 core magnetization test excitation capacity calculation test power supply on the excitation coil: power frequency 50HzAC excitation coil turns calculation: f test power frequency, HzB core yoke actual magnetic flux density, T; S stator core yoke cross-sectional area , cm2. Actually take 4 试验 during the test.

Inductive reactance calculation of excitation coil: Xl=0.404n ​​Excitation current calculation: Measurement coil voltage calculation: Stator core active loss: Excitation capacity calculation: 1 set rated capacity 1000kVA transformer.

2 test equipment selection test power transformer selection: transformer model: SL71 (1) 0 / 6 rated capacity: 1000kVA rated voltage: 6 / 0 4kV rated current: 96.2 / 1443.3A rated frequency: 50Hz connection group: Y / Y. A 12 phase: 3-phase instruments, instruments, and material selections are not described in detail here.

4.3 Test preparation, wiring, test method 4.3.1 Winding excitation winding The stator core of the generator is stacked and compacted. After the core magnetization test conditions are met, the special excitation coil is evenly wound on the stator core.

In order to make the magnetic flux density distribution generated in the stator core uniform, eight parallel excitation coils are evenly distributed in the circumferential direction of the stator core.

Each branch of the insulated copper core soft electric cable passes about 125A current, and one end of the 8 branches passes through 150 (/5A current transformer, and is connected to the C-phase bus of the low-voltage side of the transformer, and the other end of the 8 branches are connected together. To the A-phase busbar on the low-voltage side of the transformer.

When winding the excitation coil, the cable should be tightened and attached to the surface of the core tooth. It should not be placed in the core groove, and the insulation rubber should be padded at the corner of the core to improve the insulation strength.

4.3.2 Winding measuring coil Winding measuring coil 1匝, measuring coil adopts 1000V section 1.50mm2 rubber insulated copper core flexible cable.

Both ends of the measuring coil are connected to the measuring circuit.

When winding the measuring coil, the cable should be tightened and placed in the iron core groove, close to the bottom of the groove, wrapped around the effective core of the stator, not wrapped around the stator frame, and padded with insulating rubber at the corners of the core to improve the insulation strength.

The alcohol thermometer is arranged such that 36 alcohol thermometers are evenly arranged along the circumferential direction of the stator core, the middle and lower yokes and the teeth.

4.3.4 The thermocouple is arranged in the middle of the stator core, at the bottom of the stator slot, and 10 thermocouples are evenly arranged along the inner circumference of the stator core. On the ring plate in the middle of the stator frame, two thermocouples are evenly arranged along the circumferential direction of the outer circumference of the stator core. In the middle of the core, at the bottom of the stator groove, eight thermocouples are evenly arranged along the circumferential direction of the outer circumference of the stator core.

5 test wiring test wiring diagram see, including AC6000V power circuit breaker, SL7 - 1000 / - 0.4kV transformer, voltmeter, frequency meter, 8 parallel branch excitation winding, measuring winding.

4.4 Test data Liujiaxia Hydropower Plant No. 5 generator stator core magnetization test time: 10:10 on May 12, 2000. Far infrared imager measured temperature data: test duration: 90 min core initial temperature: 19.0C maximum tooth temperature : 30.7 °C minimum tooth temperature: 24. 4.5 Test results The actual unit iron loss is measured by the test. Due to the stator structure of the generator, the excitation coil and the measuring coil actually surround the stator frame during the test, so that the stator core unit loss is too large. , slightly larger than the standard of 1.9841W/g.

The potentiometer measures the highest temperature rise of the stator core teeth (flux density conclusion: the highest temperature rise of the stator core teeth is less than the standard specified 25 IC potentiometer to measure the maximum temperature difference of the stator core teeth (magnetic flux density table 1 electrical parameter record data sequence time test Frequency excitation voltage U2 Excitation current 11 Induction voltage U. Power P No. Conclusion: The maximum temperature difference of the stator core tooth is less than the standard specification 15K. Table 2 Actual magnetic flux density and unit iron loss serial number Actual magnetic flux density B (D far infrared imager The highest temperature rise of the stator core tooth (magnetic flux density: L conclusion: the highest temperature rise of the stator core tooth is less than the standard 25IC far infrared imager measured the maximum temperature difference of the stator core tooth (flux conclusion: the maximum temperature difference of the stator core tooth is less than the standard 15K) (6) The summary test data meets the requirements of the specification. The stator frame, the stator core positioning rib, the stator core pressing screw and other parts have no abnormal phenomena during the test, and the stator core magnetization test is qualified.

Table 3 potentiometer measured temperature data °C test time (min) position number core inner circle center frame ring plate 12 core outer circle middle center iron core average temperature base average temperature 5 large hydro-generator stator core stack The feeling of the core magnetization test is that the requirements for the quality of the stator core stack are getting higher and higher as the single-unit capacity of the large-scale hydro-generator is getting larger and larger. Through Liujiaxia No. 5 generator stator core stacking, core magnetization test and domestic and foreign large-scale hydro-generator manufacturing experience, if the stator core stacking quality is excellent and the core magnetization test meets the specifications and standards, the construction process must be strictly controlled. quality specifications technical requirements, but must pay attention to the following questions.

5.1 stacked stator core according to process requirements and manufacturing process of the stator assembly drawing Manual of core laminations, stacked punchings first test period of about 2, and each punching into two positioning bars, shaping work. At this time should be checked properly positioned dovetail groove rib punching position, the outer peripheral surface of the core uniformly smooth, while checking and adjusting the position of the platen means to ensure that the finger pressing the punching teeth tooth relative timing. Formal laminations, the first positioning rib dove tail section of a thin coat of molybdenum disulfide, while checking the height of each of the core segment, and to reserve the amount of highly compressed core 0.6mm, the height of each segment error range allowed laminated stator core value in order to avoid errors during lamination, lamination method using single full turn clockwise, clockwise shifted 1/4 interlayer punching, while ensuring consistent marker of each punching direction.

Any damaged or punching scrap ventilation slots and the quality of the sheet.

Each core segment is measured at least twice after the lamination.

In the position of the core ventilation groove, the starting positions of all the ventilation slots should be consistent with each other.

Be sure to place a piece of chamfered piece on each of the ventilation slots.

5.2 stator core pre-compression process requires that each segment of the core lamination height reaches about 450mm, the pre-stressing tool is installed to pre-compact the iron core, and the core is subjected to plastic inspection. The inner diameter, the undulation and the length of the core should be measured for each preload and recorded so that the lamination height can be adjusted later. When tightening, use 4 wind triggers 90 to gradually tighten in the same direction until the preload is checked with a torque wrench. Meet the requirements.

5.3 When the core is finally pressed at a distance of about 100 mm from the upper end of the core lamination, a pressure test is performed to ensure that the final stack height of the core is within the design requirement of 2131.13 mm, that is, the punching sheets are stacked in the 90 direction and are consistent with the total height requirement. Tightly, after the height is determined, remove the punching pieces, stack the punching pieces to the expected height as required, then install the upper fingerboard, adjust the position and perform the final pressing work.

4 Epoxy coating treatment of the stator core The stator core tooth bonding is surface-coated with an epoxy adhesive, and the permeability thereof is infiltrated into the sheets to achieve the purpose of bonding the teeth after curing. The method is to uniformly coat a layer of epoxy adhesive on the surface of the core with a brush, and the middle part is required to infiltrate the core without dripping, and the upper and lower ends are coated with a plurality of epoxy adhesives until Then there will be a phenomenon of infiltration. Note that the epoxy adhesive material should not be used for more than 3 to 4 hours. Excessive adhesive flow should be wiped off before the epoxy adhesive material is cured.

5.5 Quality Assurance Measures The quality control and inspection of the stator core assembly work shall be strictly carried out. The self-inspection of the technicians of the construction team shall be carried out. The competent engineer shall re-examine the quality record after submitting the inspection. The supervision engineer shall finally accept the inspection and issue the certificate to carry out the next process. Process control of construction. The production and construction shall be organized in strict accordance with the installation process, quality standards provided by the manufacturer and the construction plan approved by Party A. The appliances, instruments and meters used in the construction shall meet the measurement requirements and shall be within the validity period of the verification.

6 Conclusion Through the stator core lamination and core magnetization test of No. 5 generator of Liujiaxia Hydropower Plant, it is proved that only strict implementation of various process standards, strengthen supervision over the specific construction process of each process, implement supervision system, and strictly implement quality three-level acceptance. The system can guarantee that the various processes are carried out in accordance with the normative standards. When performing the core magnetization test, it is necessary to strengthen the monitoring and measurement of the temperature and temperature rise of each part of the stator core while measuring the unit loss of the stator core. Only in this way can comprehensive monitoring be performed to ensure the quality of the core magnetization test.

If only the unit iron loss is evaluated and the stator core is partially overheated, the stator core is bulky and does not have a significant impact on the unit iron loss. Therefore, when measuring the unit iron loss, the stator core is monitored and measured at all times. The temperature and temperature rise of each part are of great scientific value.

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