This paper analyzes the digital signal processing techniques and estimates induction motor (IM) rotational speed operating in stationary or non-stationary conditions. Rotor slot harmonics present in the stator current waveform are used to estimate the induction motor speed with a given or identified rotor slot numbers. This paper’s contribution is the following: First, zoom improved short-time Chirp-Z transform is used to find supply frequency and the rotor slot harmonic frequency to improve the estimation accuracy without increasing computing complexity. Second, a technique is described that can be used to determine whether or not a motor can generate principal slot harmonics (PSH). Finally, an algorithm is designed to figure out the perfect window length and estimate the motors’ speed. This proposed technique was investigated when the motor was fed by an inverter-fed supply driving a variable load and operating in non-stationary conditions. Experimental test results on 5.5 kW and 22 kW induction motors have confirmed the correctness of this method.
To achieve high-accuracy dynamic rotor temperature measurement of an explosion-proof motor during operation, a novel measurement method with a new-type FBG (Fiber Bragg Grating) sensor, is proposed in this paper. First, a new kind of FBG temperature sensors which could be employed in the narrow and small spaces of a motor�s air-gap with microsize sealing was developed. Experiments have shown that the designed sensor has a linearity of 0.999, and a repeatability of greater than 274.5 K within the range of 323 K�443 K. Second, a rotor temperature test system with designed sensor was built; the test results showed that the error between the test results and simulation results was less than 8%, which verified the feasibility and validity of the presented method. Furthermore, introducing an all-optical signal into the motor�s measurement field, this method was characterized by good fitness, immunity to electromagnetic interference, good explosion-proof performance, high accuracy, dynamic measurement, etc. Therefore, this method could be widely applied to the motor measurement field.
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