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US 9,431,949 B2Granted
Induction motor speed estimation
AssigneeGeneral Electric Company
InventorsPinjia Zhang, Prabhakar Neti, Patel Bhageerath Reddy
Life of this patent
Estimating the term…
Abstract
A method for estimating a speed of an induction motor includes applying a voltage to the induction motor and measuring a current of the induction motor. A current fast fourier transform (FFT) of the current is then determined and a slip of the induction motor is calculated based on the current FFT. A speed of the induction motor is then estimated based on the slip of the induction motor.
Claims14
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.
5 more elements
A system, comprising:
- a power supply to provide a voltage to an induction motor;
- a measurement unit to measure a current of the induction motor;
- a processor to estimate a speed of the induction motor, the processor comprising:
- a fast fourier transform (FFT) module to determine a current FFT of the current;
- a slip calculation module to determine a slip of the induction motor based on the current FFT;
- a speed calculation module to estimate a speed of the induction motor based on the slip of the induction motor;
- wherein the slip calculation module determines the slip of the induction motor based on a misalignment frequency calculated from the current harmonic, a rated frequency and a number of poles;
- wherein the slip calculation module is configured to determine 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
- wherein the processor is further configured to determine 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.
7 more elements
Dependencies are inferred from the claim text.