Angular sampling of wind turbine low-speed shaft using high-resolution magnetic keyphasor

Precise angular measurement of low-speed shaft is important for condition monitoring and fault diagnosis of Wind Turbine (WT) drivetrain operating at low speed. A high-resolution keyphase device, consisting of a magnetic grid and a magneto-resistance sensor, is proposed to measure the rotating angles of WT low-speed shaft. A flexible magnetic grid was attached around main shaft tracked with an anisotropic magnetoresistance (AMR) sensor whose acquisition frequency beyond several hundred kHz. Firstly, the measurement system can generate micron-scale pulses in equal angle and instantaneous angular speed (IAS) can be easily obtained from counting these pulses. Furthermore, the high-resolution magnetic keyphasor is used as a trigger source for vibration signal acquisition. Therefore, order spectrum of low-speed drivetrain vibration can be easily constructed based on Fourier transform of the acquired vibration signals. Design of measurement system is introduced in details and experimental results are shown to prove the concept. The designed device, with high resolution and high stability, is easy to install on site. The proposed angular measurement system facilitates not only reliable IAS measurement, but also better fault diagnosis of WT drivetrain.