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The new type of pumping station motor construction and assembly method is pre-set optimally

06 Nov 2020Email

The new type of pumping station motor construction and assembly method is pre-set optimally

 

 

1 Project Overview
The Jiangjian Water Conservancy Project is one of the backbone urban flood control projects in Wuxi, located near the Jiangjian Bridge on the ancient canal. The project mainly includes a 60m3/s pump station and a 3-hole control gate with a total width of 75m. Among them, the pumping station is 3 sets of 20m 3/s shaft tubular pumps, equipped with 800kW asynchronous motors, and parallel shaft gear reducers to transmit power.

 


2 Common problems of shaft tubular pump
(1) After the equipment is arranged, the space in the shaft is small and the operation and management are inconvenient.
(2) The conventional wiring of the motor cable is at the side or top, but this wiring method is used in the shaft, which not only affects the appearance, but also cuts off the channel in the shaft, which is not convenient for operation and management.
(3) Adopting natural air intake and ducted exhaust air not only has an unsightly layout of the air ducts, but also the motor has a high operating temperature and poor heat dissipation conditions.
(4) The high-speed operation of the motor is noisy.

 


3 Optimization measures for main motor
3.1 Improve the performance index of the motor In order to improve the electromagnetic performance of the motor, the design value must exceed the requirements of the bidding document, and its various index requirements are listed in 1. The guaranteed value in the table does not allow tolerance. Jiangjian Pumping Station is a drainage pumping station in the urban area, with less running time. The focus of motor design is to reduce operating noise, lower operating temperature, increase starting performance, and appropriately improve motor efficiency and power factors.
3.2 Reduce the operating temperature of the motor Since the shaft is small and a relatively closed space, the natural air intake and mechanical exhaust methods are not very suitable. For this reason, the air-water cooling method is adopted, that is, the inside of the motor is air-cooled, and there is a reasonable air circulation loop. The hot air of the motor is cooled by a water cooler. This cooling method is superior to the full air cooling method and is not affected by the shaft space. Impact.
3.3 Improved structural design The size of the motor is required to be compact, reducing the space occupied by the shaft. The junction box of the motor cable is not conventionally designed and arranged at the end of the motor. There is a tail bearing at the end of the motor. Although it is difficult to arrange the cables inside the motor, it is beneficial for operation and maintenance.
3.4 Prevention of operating noise There are three sources of noise: fan and wind circulation noise, mechanical noise, and electromagnetic noise. The following prevention measures are mainly adopted:
(1) Cancel the fan. After the air-water cooling method is adopted, there is no need for an air inlet. The inside of the motor is a closed space, and the internal wind noise is basically not transmitted to the outside. After improving the motor protection level, the motor noise is further reduced.
(2) Use SKF's low-noise rolling bearings and its supporting LGEP2 special grease to reduce bearing operating noise.
(3) Improve the rigidity of the base and the end cover, improve the balance of the rotor (after the rotor is assembled as a whole, perform a dynamic balance test), and reduce mechanical vibration and noise.
(4) Choose a reasonable tank fit for mature products. The slot coordination of the stator and rotor of the squirrel-cage asynchronous motor has very strict restrictions. Improper selection will produce larger parasitic synchronous torque, tangential parasitic force of parasitic asynchronous torque, and radial parasitic force that changes simultaneously. These parasitic forces deteriorate the starting characteristics of the motor, and the radial parasitic forces cause periodically changing unidirectional suction force, causing the stator and rotor to vibrate, which is an important source of noise in the motor. Different schemes were analyzed and compared for the matching motor of the shaft tubular pump, and the experience of other projects was absorbed, and a reasonable groove fit was selected, which effectively reduced the above-mentioned parasitic force and suppressed the noise of the motor during startup and operation.
(5) Choose a lower magnetic load during design, that is, reduce the magnetic flux density of each part.
(6) The rotor winding is welded with copper bars and end rings (without cast aluminum structure) to improve the three-phase balance of the circuit.
(7) The stator and rotor punching pieces are made of high-quality silicon steel sheets with low loss, high magnetic permeability, and good flatness, and processed by a non-burr high-speed punching machine, so that the lamination coefficient of the stator and rotor punching pieces is above 0.96, and the core compression It can reduce the magnetic noise of the iron core when the motor is running.

 


4 summary
By adopting the above measures, the above-mentioned problems have been effectively solved, and the results have been good after many running tests after the completion of the project.

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