April 18, 2018
Many companies have spare electric motors in their warehouse in the event of a critical motor failure. Many times this can be an intelligent decision, allowing for quick change out in the event of a failure (or pending failure) or during a scheduled outage or shutdown. It is important to have a plan for when …
January 4, 2018
The below video is a 15 minute segment of an hour long presentation given by Todd Hatfield of HECO at the 2017 Reliability, Process, and Maintenance (RPM) Symposium. This presentation discusses common preventable causes of electric motor failures. This section of the presentation discusses bearing related failures as bearings account for about 51% of all …
January 11, 2017
Todd A. Hatfield – Vice President of Engineering & Repair, HECO This is the third article (video) in a series of articles on The Basics of AC Induction Motors. The first video explored the basic principles of AC Induction motors focusing on magnetism, electromagnetic induction, AC current, and rotating magnetic fields. The second segment discussed …
January 3, 2017
Shaft currents can have a destructive effect on electric motor bearings. This article, with information from our friends at AEGIS Shaft Grounding Rings, is intended to inform professionals about these voltages and their effects on bearings in electric motors. Because of the high-speed switching frequencies in PWM inverters, variable frequency drives induce shaft currents in …
December 1, 2016
Todd A. Hatfield – Vice President of Engineering & Repair, HECO This is the second article (video) in a series of articles on The Basics of AC Induction Motors. The first video explored the basic principles of AC Induction motors focusing on magnetism, electromagnetic induction, AC current, and rotating magnetic fields. This segment discusses the …
November 14, 2016
Todd A. Hatfield – Vice President of Engineering & Repair, HECO This is the first article (video) in a series of articles on The Basics of AC Induction Motors. This video explores the basic principles of AC Induction motors. This segment discusses magnetism basics, the law of electromagnetic induction, AC current, and the explanation of …
August 11, 2016
Before reading about these different tests, please check out our last few articled on electric motor theory and rotor bar cracks: How Does an Induction Electric Motor’s Rotor Work? How do 2-pole Electric Motor Rotor Bars Crack? Besides a simple visual inspection, below is a summary of the most common methods of detecting cracked rotor …
August 4, 2016
Rotor bars of 2-pole (3600RPM) rotors are subjected to high stresses caused by repeated starting, thermal expansion and centrifugal forces. The repeated starting with resultant cyclic forces causes the bars to loosen. This is because the rotating magnetic stator field applies rapidly alternating forces to each rotor bar, diminishing in intensity and frequency as the …
July 28, 2016
The induction of current flow through an induction electric motor’s rotors bars occurs when current is applied to the stator. This applied current through the stator windings starts the rotation of the stators magnetic field at line frequency. The rotor bars of the stationary rotor are then subjected to the maximum relative motion of the …
July 19, 2016
Shaft circulating currents are caused from “dissymmetries” in the magnetic paths through the stator and rotor iron. As the rotor rotates within the stator and as the stators magnetic field rotates, small differences in the magnetic “reluctance” of the core parts generate small voltages between the ends of the shaft. As you can see from …
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