Direct current machine monitoring system and method

The invention relates generally to direct current machines and more particularly to direct current machine monitoring systems. A direct current machine monitoring system includes a current sensor for monitoring load current of the machine; and a computer for obtaining a power spectrum in a range including a machine trait-passing frequency, determining a magnitude of a maximum peak in the power spectrum in a range including the trait-passing frequency plus or minus an uncertainty frequency, and evaluating the magnitude of the maximum peak to assess a condition of the machine. The computer may additionally or alternatively be used for obtaining a low frequency power spectrum of the load current, obtaining at least one magnitude of a component of the power spectrum at a respective predicted frequency, and evaluating the at least one magnitude of the component to assess the condition of the machine.