Collector ring assembly

key word：Heat exchange element

Category:

Generator excitation system

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Product description

The collector ring assembly consists of the collector ring assembled on the small shaft, the lower insulating sleeve of the collector ring, the fan, the conductive screw and the conductive rod, and is connected with the generator rotor through the end coupling of the small shaft. The collector ring is made of 50Mn forged steel. The outer surface of the collector ring is provided with spiral heat sink, and the axial direction is distributed with inclined ventilation holes along the circumference.

The collector ring is usually with a diameter of ∮ 450mm + 1%, and the surface roughness is generally 1.6mm when leaving the factory. In the positive and negative collector rings, the width of the whole collector ring is 160mm. The collector ring of each pole is divided into two rows, each row is 38mm ~ 40mm wide, which is used to contact the carbon brush and input DC into the rotor to establish the rotor rotating magnetic field. There are 14 carbon brushes in each row, and there are 56 carbon brushes in 4 rows. If the maintenance is appropriate, the collector ring life expectancy is generally about 20 years.

Compared with other electrical equipment, collector ring maintenance is much easier and simpler, mainly including the following points:

1.1. Keep clean. Keep the collector ring surface smooth and clean, especially in wet places. Clean the collector ring surface with dry and clean compressed air when the unit is shut down.

1.2. Select matching carbon brushes. The types and quality of carbon brushes on the market are uneven, especially the graphite content of some products is too low, and the internal hard impurity content is too high. This kind of carbon brush will cause ring fire on the surface of collector ring due to wear soon. And because of the bad contact, the resistance between the collector ring and the carbon brush becomes larger, which makes the temperature between the collector ring and the carbon brush higher. The carbon brush hard impurities will wear the collector ring out of the uneven channel, and the electric corrosion occurs in the channel, causing the collector ring surface wear and vicious cycle. In general, D172 soft carbon brush can prevent similar phenomenon. Before replacing the carbon brush, it is better to process a simulated collector ring, which is rolled with 20 mm thick steel plate and welded with 10 mm thick steel plate inside. Then the outer diameter of the ring is machined to ∮ 454 mm (1 mm ~ 2 mm smaller than the collector ring). The selected capacity is 2kW The simulation collector ring is installed on the motor, and a number of carbon brush holders and carbon brushes are installed at corresponding positions. The abrasive cloth is fixed on the outer circle of the simulation collector ring, and the motor is started to grind the carbon brush from coarse to fine (finally with metallographic sandpaper) to the required curvature radius. The more accurate the mechanical parameters are, the better the curvature radius of the carbon brush is, and it is best to replace the carbon brush every time Only one or two brushes should be replaced in each row, and the carbon brush holder should be installed perpendicular to the tangent line of the plane where the collector ring is located, so as to ensure that more than 85% of the whole carbon brush surface is in contact with the collector ring.

1.3. full contact between carbon brush and collector ring

At present, the location of collecting ring and carbon brush of 200MW generator rotor is basically coincident with the center line of each row in cold state. Because the relative dead center of the steam turbine rotor is at # 2 pad, and the dead center of the cylinder is between the medium and low pressure cylinders, under the rated load, relative to the static dead center position of the steam turbine, the elongation of the rotor due to expansion is about 5.6 mm ~ 8 mm, and the direction is the generator side. The allowance of each row of collector ring is [(38 ~ 40) - 25] / 2 = 6.5mm ~ 7.5mm, that is to say, if the carbon brush is adjusted to the middle line of each row in cold state, when the rated load is on, because the shaft will extend 5.6mm ~ 8mm to the excitation end, the left row of carbon brush in each pole of collector ring will run to the outside of collector ring, while the right row may run to the ventilation ditch, which is not conducive to the safe operation of the unit. In order to ensure that the carbon brush is on the center line of each row during normal operation, the motor and the steam turbine should be installed in strict accordance with the technical requirements, that is, the generator rotor should be offset to the steam turbine in the cold state to offset the expansion to the generator side in the hot state.