Training Course: AC Motor Troubleshooting Basics

Do you have an electric motor that’s having problems, but you’re still not ready to call the repair shop yet? Whether you need some direction in figuring out a problem, or you just want to prepare your business in case of future disaster, Brooks Motor & Electric is here to help you learn. One of our field technicians recently taught a class about the basics of AC electric motor repair. We’ve captured the relevant portions of the class on video and made them available to the public.

If you’re completely new to the internals of an electric motor, start with the video on this page (embedded below); it covers the very basics and fundamentals. If you’re up to speed on motor design and construction, try the next video. In it, David addresses the mechanics and theory behind the operation of electric motors. Once you’re up to speed on the basics, we have videos to assist with general mechanical troubleshooting, water pump troubleshooting, and a more in-depth guide to troubleshooting motors based on their electrical readings.

If you’re interested in the course as a whole, this video is part two. In this twenty-minute portion of the lesson, David presents the fundamentals of electric motor construction and design and answers relevant questions from the audience. For a more detailed view of the slides used in this video, see pages five, six, and seven of the course workbook. Please note, this course was designed for municipal utility employees and was recorded live.

Video Synopsis

Electric Motor Design: The most important components of a three phase AC motor are discussed. These include the case, the stator core, the coil, the rotor, and the bearings. David explains the purpose of each component as well as cues to look for when trying to diagnose simple equipment failure.

Horizontal Motors and Vertical Motors: Horizontal and vertical motors are functionally very similar, and can even be used interchangeably in some circumstances. However, there are many use cases where the differences between them is significant, and using the appropriate style can be very important. The most notable difference between them is bearing selection and placement. In a motor specifically designed to be mounted vertically, additional bearings are used to increase the motor’s life and effectiveness.

Single-Phase AC Motors: Single-phase electric motors are more complex than three-phase motors, and as such, are more cumbersome to troubleshoot – or as David describes them “a nightmare to troubleshoot … and repair.” Additional capacitors, switches, and dual windings add multiple points of failure that make single-phase motors difficult to work with. Whenever possible, a three-phase motor is always preferred to a single-phase motor.

Three-Phase Motor Fundamentals: A three-phase motor is wired with three sets of windings, A, B, and C phase. These three phases of windings are wired together in such a way that a magnetic field is generated, causing the motor to turn. A general understanding is established, but a more advanced discussion of three-phase circuits is included in the next video.

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