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Surge testing and Error Area Ratio (EAR) basics

Publication date: 
July 2016
Mike Howell, EASA Technical Support Specialist
Type of media: 

Most service centers perform some form of surge comparison testing, though terminology and methodology may vary. In simple terms, two winding responses or waveforms from a fast rise-time surge are compared and if there is an excessive difference, the unit under test may have a defect. The waveform that is produced by the pulse is unique to the unit under test, which for example, could be a stator winding. The waveform will be a function of the resistance, capacitance and inductance of the test circuit and quite a few variables can affect those characteristics. 

Topics discussed:

  • What is EAR?
  • Pulse-to-Pulse (P-P EAR)
  • Line-to-Line (L-L EAR)
AC motors
Motor testing