A Simple Approach to Duty Ratings of AC Machines - Webinar Recordings - EASA | The Electro•Mechanical Authority
Facebook Twitter LinkedIn YouTube Menu Search Arrow Right Arrow Left Arrow Down Arrow Up Home Arrow Next Arrow Previous RSS Icon Calendar Icon Warning Icon
NOTICE: The EASA office will be closed Friday, July 4, 2025 for Independence Day in the U.S.
Trainingbreadcrumb separatorWebinar Recordings

Filter the results

  • Enter one or more words to find resources containing any of the words entered
  • Enter words or phrases between " " to find exact match
SearchClear

Webinar Recordings

Trade press article — Electrical Construction & Maintenance

A Simple Approach to Duty Ratings of AC Machines

How to ensure the correct duty rating for each application

  • April 2022
  • Number of views: 5679
  • Article rating:

Matthew Conville, MBA, PE
EASA Technical Support Specialist

Before putting an AC machine into service, make sure its duty rating matches the application requirements. Otherwise, there’s a good chance excessive heat will degrade the machine’s windings.

Applications are not all created equal. For example, a crane motor doesn’t require the same duty rating as a punch press motor of equal horsepower that runs continuously. Likewise, a chop saw motor wouldn’t need the same duty rating as a pump motor that operates 24-7-365. If the motor must operate at variable speeds other than its nameplate base speed, its turndown ratio is another consideration.

NEMA Std. MG-1-1.40 and IEC Std. 60034-1, Clause 4 describe the duty classifications for the respective standards.

  • NEMA duty classifications
  • IEC duty types with "S" ratings
  • Turndown ratios
  • Questions to consider

READ THE FULL ARTICLE



Related Reference and Training Materials

Principles of Medium & Large AC Motors (NEMA Standards)
Principles of Medium & Large AC Motors (IEC Standards)
Tags: Duty ratings
Print

Comments are only visible to subscribers.