1. Apparatus for detecting a departure from normal operation of an electric motor, comprising: sensing means for measuring a set of current values for a motor being monitored; first signal processing means coupled to said sensing means for deriving frequency spectral components associated with said set of current values; a neural network auto-associator coupled to said first signal processing means and further coupled to said sensing means for receiving at least a portion of said frequency spectral components and at least a portion of said set of current values as an input vector and having output terminals for providing an output vector; and second processing means coupled to said output terminals for comparing said input and output vectors for providing an error metric.