Advanced Motors

SKU: RVI-11508Duration: 20 Minutes

This course addresses the more advanced maintenance practices to ensure electric motor long term reliability. An overview of various motor types, construction, and applications is discussed. The NEMA (National Electric Motor Association) mountings and dimensional data of different frame sizes of motors is presented to assist maintenance personnel in the selection and maintenance of facility electric motors. Lastly, energy efficient motors are reviewed to allow a better understanding of how their use can reduce operating costs.

Course Details


Training Time: 20 minutes

Compatibility: Desktop, Tablet, Phone

Based on: Industry Standards and Best Practices

Languages: English

Learning Objectives

  • List advanced motor maintenance tests
  • Identify various winding configurations
  • Explain types of motors and their application
  • Identify NEMA frames by their suffix
  • Describe overload relay maintenance procedures
  • Explain the principles behind energy efficient motors

Key Questions

The following key questions are answered in this module:

What is voltage unbalance?
Voltage unbalance degrades the performance and shortens the life of a 3-phase motor.

What are the two 3-phase motor configurations?
A 3-phase motor may be set up in Y type or Delta type.

How can condensation problems in motors be avoided?
Condensation problems in motors can be avoided by maintaining a winding temperature of 5 to 10 degrees centigrade above the surrounding air temperature.

What is the most common type of AC enclosed motor?
The Totally Enclosed Fan Cooled (TEFC) motor is the most common as it has an external fan mounted on the non-driven end of the shaft and enclosed with a shroud for safety.

What is "efficiency" regarding electric motors?
For an electric motor, efficiency is the ratio of mechanical power delivered by the motor (output) to the electric power supplied to the motor (input).

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

Motors can be damaged by excess heat caused by current flow when there are overload conditions. Installing overload relays in your applications can protect your motors. When a motor starts, it typically requires six times the full-load current rating. After the motor ramps up to operating speed, the current drops off. Motors are designed to handle this overload condition for a short period. If a motor maintains this overload condition, the motor will overheat and potentially become damaged. Fuses and circuit breakers can protect a system from short circuits, ground faults, or overload, but they are not the proper protection device for motors. Motors pull significantly more amps at startup than their full-load current rating. Any fuse used with a motor would need to be rated to handle this higher startup amp draw; therefore, it would fail to protect the motor from overload conditions beyond normal startup. Overload relays are designed to allow temporary overloads for a specific period during startup. If the overload persists, the overload relay will trip and break the circuit to protect the motor. Overload relays can be easily reset after the overload is corrected. Overload relays have a trip class rating for different applications. The most common trip classes are Class 10, Class 20, and Class 30. The number in a trip class is the total number of seconds that the motor can overload before the circuit trips.
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