October 24, 2016
Before Reading – Please see the first article in this Case Study Series: “On-Site Findings.” The results of the “on-site” findings resulted in the determination to pull this Boiler Feed Pump Motor (9000HP, 1800RPM, 13,200v, Siemens Allis) out for repair. The motor was removed and was received by the HECO motor repair shop on 3-31-2015. …
October 8, 2016
On March 09, 2015, HECO was called in to help evaluate vibration and noise concerns with a coal-fired power generation plant’s Boiler Feed Pump Motor. (9000HP, 1800RPM, 13,200v, Siemens Allis). Initial information from the plant vibration team indicated rotor related issues. Review of the data provided showed a possible rotor bar pass frequency. This is …
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 …
July 14, 2016
This is our third and final article in a series of articles on ball bearings in electric motors. You are encouraged to view our prior articles at the links below: Electric Motor Ball Bearings Types & Options Greasing Electric Motor Ball Bearings This article picks up where those left off… What else should you consider …
July 8, 2016
Before reading this article, please first read our article on Ball Bearing types and options. That is the first article in this series of articles on electric motor ball bearings. This article is focusing on some factors to consider when greasing ball bearing motors. There is a variety of useful information in this article, but …
June 29, 2016
Most electric motors in industrial facilities consist of rolling element bearings, either ball bearings or roller bearings. We will explore these different types of bearings and sealing methods in this article. Ball Bearing Used in direct coupled applications. These can handle axial as well as radial loads. Roller Bearing Used for belted applications, generally in …
May 19, 2016
VPI (Vacuum Pressure Impregnation) is a process that is a technological step forward from varnishing electric motors. The old dip and bake (in varnish) method of “insulating” motors is replaced by the VPI process for specific reasons: Harsh Environment Improved Efficiency (through better heat transfer) Improved Mechanical Winding Design When electric motor repairs proceed as …
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