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Motor nameplate ratings: How precise are they?

  • December 2012
  • Number of views: 4594
  • Article rating: No rating

Tom Bishop, P.E. 
EASA Senior Technical Support Specialist

Correct interpretation of five operating parameters for NEMA, IEC induction motors When someone reads an electric motor nameplate, the normal assumption is that the information can be used at face value. That applies to some but not all of the nameplate information. For example, the power rating (hp or kW) and frame size are specific to the motor. However, ratings such as voltage, frequency, current, speed (rpm) and efficiency have tolerances associated with them. Our focus in this article will be to discuss the correct interpretation of each of these five operating parameters for induction motors of both NEMA and IEC design. Topics discussed include: Voltage and frequency - NEMA MG1-12.44 and IEC 60034-1.7.3 Current - NEMA MG1-12.47 and IEC 60034-1 Speed (rpm) - NEMA MG1-12.46 and IEC 60034-1-12.1 Efficiency - NEMA MG1-12.58 and IEC 60034-1 Note: The letter codes for insulation class, design and kVA code that appear on NEMA motor nameplates are addressed in "Motor Nameplate Letter Code Designations" in the March 2009 issue of Currents.

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ANSI/EASA AR100

More information on this topic can be found in ANSI/EASA AR100
  • Section 1: General
  • Section 4: Testing

EASA Technical Manual

More information on this topic can be found in EASA's Technical Manual
  • Section 2: AC Machines

Related Reference and Training Materials

Principles of Medium & Large AC Motors (NEMA Standards)
  • Section 1: Motor Nomenclature & Definitions
  • Section 3: Typical Motor Applications
  • Section 5: Basic Motor Theory

Principles of Medium & Large AC Motors (IEC Standards)
  • Section 1: Motor Nomenclature & Definitions
  • Section 3: Typical Motor Applications
  • Section 5: Basic Motor Theory

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Tags: Nameplate Motor nameplate Induction motor
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