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How to Get the Right Electric Motor, Part 3 – Understand Basic Motor Configurations - HECO

November 21, 2023

Selecting the correct replacement for an electric motor is straightforward – once you know exactly what you need to replace, that is! Understanding basic motor configurations and types allows you and a trusted partner to identify what you have and specify what you need in a replacement.

From standard duty and general purpose motors to severe duty and IEEE 841 options, HECO can help.

Let’s explore basic electric motor configurations.

Standard Duty or General Purpose Motors

Typical general purpose motors are designed and manufactured to have open drip-proof (ODP) enclosures or totally enclosed fan-cooled (TEFC) enclosures and are regulated to ensure that they meet NEMA’s efficiency regulations.

These motors typically have ball bearings (or roller bearings for high radial load belted applications) and can range from having a frame that is made out of flat-rolled steel, cast aluminum, or cast iron. Warranties on general purpose motors vary from brand to brand.

General purpose motors are used in a variety of everyday, normal applications and industries including pumps, fans, compressors, conveyors, etc.

Severe Duty Motors

Designed to stand up to harsher conditions, such as humidity, heat, and corrosive or mechanical stresses, severe duty motors go beyond the capacity of a general purpose motor.

Severe duty motors only have TEFC enclosures. Features of these motors vary from manufacturer to manufacturer based on what they consider severe duty.

Overall, severe duty motors are made for tougher applications and environments such as chemical processing, mining, foundry, pulp and paper, waste management, and petrochemical applications.

IEEE 841 Motors

For motors that require more than severe duty specifications, the IEEE 841-2009 standard is used. This specification covers three-phase motors from 1 to 500 hp with 3600, 1800, 1200, and 900 rpm.

IEEE 841 motors feature:

  • Cast iron construction.
  • Totally enclosed, NEMA Design B torque/current characteristics.
  • Bearings with designed L-10 life.
  • Limited shaft runout.
  • Non-sparking fans.
  • IP55 cast iron terminal boxes.
  • Sound reduction to 90 dB.
  • Low vibration tolerance.
  • Corrosive-preventive coatings.
  • Non-contacting–while-rotating seals with a minimum expected seal life of 5 years (typically Inpro/Seal).

Although these motors were specifically designed for the petrochemical and chemical industry, their premium features are used in a variety of other industries and applications such as cement and aggregate plants, power generation facilities, and paper, pulp, and steel mills.

These motors can be used indoor or outdoor in humid, chemically corrosive environments where ambient temp ranges from -13º to 104º F (-25º to 40ºC) and the altitude does not exceed 3,280 ft (1000m).

IEEE 841 motors can also be used in conditions where there’s a +10% of rated voltage @ rated frequency, a +5% of rated frequency @ rated voltage, and a combination of voltage and frequency variation of 10% within limits above.

For further information on IEEE 841 specification motors, download the entire spec.

All Systems Go

With decades of experience selling, servicing, and monitoring electric motors and rotating equipment, HECO has the knowledge and a customer-focused staff dedicated to helping you evaluate your electric motor configuration needs.

Contact us to discuss your existing motor and what you would like to achieve with its replacement.

For additional information, download HECO’s How to Get the Right Electric Motor e-book.

To date, the How to Get the Right Electric Motor series includes:

Upcoming posts in the series will include:

  • Part 4 – Consider Non-NEMA, Larger Options.
  • Part 5 – Pay Attention to Specifications.
  • Part 6 – Compare Expectations of New & Rebuilt Systems.

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