Motor Current Signature Analysis on DC Motor


Evaluation of a 10 HP, 1.0 SF, Ins F, 1750 RPM, 240 V, 33 Amp armature, 240 V, 1.23 Amp field, DC electric motor from the output of the DC Drive. A DC Drive fault and poor brush condition were indicated.


When testing a DC electric motor with the ALL-TEST PRO™ OL (ATPOL) motor current signature analyzer, it is recommended that the AT6000 DC Clamp is used for analysis. Data is collected directly from the armature leads.

Running speed is selected and current ripple viewed. Variations in the current ripple waveform indicate drive problems which can be confirmed as harmonics of supply line frequency and the number of SCR’s times the supply line frequency (Figure 4).

The signatures, Figure 1 and Figure 3, indicate power electronic and brush-related problems.


The ALL-TEST PRO™ MD kit consists of:

  • ALL-TEST PRO™ OL motor current signature analyzer
  • ALL-TEST PRO™ 31 and ALL-TEST IV PRO™ 2000 motor circuit analyzers
  • EMCAT motor management software
  • ATPOL and Power System Manager software modules for EMCAT