JPH0350513B

PURPOSE:To enable to detect the malfunction of a rotary electric machine in an early period by discriminating the malfunction of the machine by the distance between the sampled value due to n-dimensional vector obtained by Fourier analysis from the detection signal and the reference value. CONSTITUTION:After the detection signal of a rotary electric machine 1 is converted by a signal input unit 3 into a digital signal, and the signal is inputted to a data storage unit 4. This input data is analyzed by a Fourier analyzer 5, which generates a sampled vector of n-dimensional vector formed of power spectral density or coherence. A reference pattern correcting unit 7 outputs a reference vector in response to the rotating frequency of the sampled vector. A comparator 8 applies a signal to an alarm generator 10 when the distance between the reference vector and the sampled vector is larger than the threshold value. In this manner, the reliability of the detected result of the malfunction state can be improved.