Application example of fan condition monitoring based on physical structure of gearbox

It is tested and verified on a 1.5 MW wind turbine in a wind farm. The gearbox of the fan is a two-stage planetary and one-stage parallel structure, and there are two main shaft bearings on the transmission chain. According to the structural characteristics of the transmission chain components, piezoelectric sensors are deployed at seven positions, including the main shaft bearing, the first stage planetary ring gear, the second stage planetary ring gear, the high-speed shaft bearing and the generator bearing, to collect vibration signals. A photoelectric sensor is fixed near the output shaft of the gearbox to collect the speed pulse signal of the high-speed shaft to calculate the speed of the high-speed shaft.

The data acquisition equipment can collect 1-way speed signal and 7-way vibration signal, and store, preprocess and distribute them at the same time. The collected parameters are configured by the wind farm control center and then transmitted to each fan. When the data file is collected and generated, the preprocessing operation will be carried out automatically. After the data reduction, the connection will be established with the wind farm control center server for transmission. When the network fails, it will be temporarily stored locally.

The physical structure of the gearbox in the fan: in the first stage planetary gear, the number of ring teeth is 102, the number of three planetary gears is 39, and the number of sun teeth is 24; in the second stage planetary gear, the structure is the same as that of the first stage planetary gear; in the high-speed parallel gear, the number of big gear teeth is 102, and the number of small gear teeth is 27.

The rated speed of the machine is 1 800 rad / min. in order to acquire the effective data of the main shaft and high-speed shaft synchronously with high frequency resolution and enough rotation period for TSA analysis, the original data file is 173.28 MB with the sampling rate of 51.2 K / s channel for 60 s.

Parameter setting in cycle domain processing: the number of sampling points per cycle is generally 2n, and the number of cycles is related to the relative speed of the components to be detected. Because of the fast speed of the high-speed parts, the rotation cycle per unit time is more, while the rotation cycle per unit time of the low-speed parts is less. In order to increase the frequency resolution as much as possible and reduce the amount of data to be analyzed, two parameters of each component are set separately. For high-speed components, the number of sampling points per cycle is set to 1 024, which leads to a large amount of data. Therefore, 20 cycles are reserved. However, for the bearing position of high-speed shaft, it is necessary to detect the high-speed pinion, high-speed big gear, high-speed shaft bearing and other components, and the reference axis is the high-speed shaft. For the high-speed large gear, its rotation frequency is the same as that of the medium speed shaft. The ratio of the rotation speed to the reference shaft speed is the ratio of the number of teeth of the large gear to the number of teeth of the small gear, which is about 3.8. Therefore, the number of cycles in the vibration response signal processing of the high-speed shaft position is set to 96. For medium speed components, the rotation speed is low, and the trade-off between the number of sampling points per cycle and the number of cycles is treated. The number of sampling points per cycle is 4 096, and 24 cycles are reserved. For the low-speed parts, the rotation speed is the lowest, and all cycles are reserved. The sampling points of each cycle are 4 096.

By using the proposed data preprocessing method, the data is effectively compressed to 2.15 MB and the file size is 1.2% of the original.

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