This article discusses the development and utilization of a Digital Lock-in Spectrum Analyzer to estimate the speed of a three-phase induction motor in a less invasive manner. The estimation of speed is obtained using acquisition and processing of one phase-current, without direct physical intervention on the motor. The Digital Lock-in Spectrum Analyzer uses Lock-in Amplifier principle at equally spaced frequencies. The Lock-in Amplifier implements phase-sensitive detection applied to measurement of signals under severe noise conditions.
induction motor; data acquisition; digital signal processors; Fourier transforms; power spectral density; frequency signal analysis; computational methods; harmonic analysis; speed measurements; tachometers
