Theoretical and experimental research on temperature measurement of motor rotor in variable speed process based on fiber Bragg grating sensor

Abstract

In order to realize the real-time on-line monitoring of motor rotor temperature, a Fiber Bragg Grating (FBG) temperature sensing system using fiber optic rotary joint to transmit signals was built. The effects of the acceleration of the rotor and the mounting angle of the sensors chain on the central wavelength of the FBG were studied. The temperature measurement test of a rotating shaft was carried out. The following conclusions can be drawn. The central wavelength variation of the FBG is related to the linear acceleration of the rotor surface, the density and thickness of the grating coating. For the rotor whose surface linear acceleration is within 100m/s 2 , when the thickness of the coating is within 100μm, the effect of acceleration on the center wavelength of the polyimide-coated or gold-coated FBG can be ignored. For the motors with higher linear acceleration, in order to prevent the impact on the temperature measurement accuracy, the angle between the FBG sensors chain and the rotating shaft is preferably controlled within 20°. For the motors with lower linear acceleration, the installation angle can be compromised according to the rotor surface structure. The experiment shows that the FBG temperature measurement system can run stably and measure the temperature change accurately during the variable speed process of the rotor. Compared with other rotor temperature measurement systems, the FBG temperature measurement system has a simple composition, and the sensors chain is light and small. It is a very promising rotor temperature monitoring system.