Patent ID: 9431949
Filing Date: 2016-08-30
CPC Classification: H02P

Claim Text:
1. A method for estimating a speed of an induction motor, comprising applying a voltage to the induction motor; measuring a current of the induction motor; determining a current fast fourier transform (FFT) of the current; determining a slip of the induction motor based on the current FFT; estimating the speed of the induction motor based on the slip of the induction motor; wherein the slip of the induction motor is determined based on a misalignment frequency calculated from the current harmonic, a rated frequency and a number of poles; wherein determining the slip of the induction motor further comprises determining a first frequency of the induction motor based on a relationship between the rated frequency and the number of poles of the induction motor; and determining a first current harmonic from a motor current FFT, wherein the first current harmonic has a second frequency which is adjacent to the first frequency and has a higher magnitude compared to other current harmonics which have frequencies adjacent to the first frequency.