​​EDE Electric Motor Testing


Keep it Clean, Keep it Dry, Keep it Tight!

Abstract: With the many types of maintenance techniques available to the industrial professional, there are many tools to provide a great deal of information on the quality and workings of electric motors and their processes. However, if maintenance basics are ignored, all the techniques are like three drops of rain in a drought – ineffective and futile. If the three basic rules for proper motor operation and upkeep are not followed, why bother investing in advanced technologies to confirm known problems? These three rules are keeping a motor clean, keeping it dry and keeping it tight. Without these rules, fancy equipment simply doesn’t matter! This is perhaps the oldest maintenance story of them all. 

Practical Calibration Verification Techniques

Abstract: Periodic calibration verification is accepted as a standard practice by many business operations, quality control departments, production lines, and manufacturers. Indeed, the need for calibration verification is required as part of many standardization organizations. The means to this end usually requires certain important considerations. If equipment is used for electrical test, certification of voltages and currents must be proven by the concept of standard traceability. This can mean periodic offsite shipment of test equipment, and the risk of loss or shipment damage. Or, conversely it can mean on-site visits by calibration service technicians. Either approach has benefits and drawbacks. An alternative approach is discussed in the article: self certification.

We WANT to Test, But We DON'T (really) Want to Find Anything...

Abstract: Overcoming typical testing dilemmas, particularly those related to repercussions of failing a test. Education and understanding risks are key considerations to attaining effective results.

Case study of medium voltage motor space heaters

Abstract: Strip or space heaters are specified to provide effective heating of the interior spaces of electric motors and other machines.  This article discusses the potential effects of their mis-use or mis-application.

A discussion of Practical Partial Discharge Detection Methods

Abstract: A wide variety of partial discharge detection methods are available in the modern marketplace. Benefits and drawbacks for certain techniques are discussed.

Partial Discharge; recent developments regarding IEC TS 6003418-41-2006-10
Abstract: This paper discusses some recent publications which describe the results of the present IEC TS 60034-18-41 2006-10 criteria for assessing insulation systems of low voltage stator or rotor windings. There is particular emphasis in recent articles regarding the presence and effects of partial discharge phenomena (often aggravated by VFD or voltage converters) on the insulation systems. Weaknesses in the qualification and type tests are commented upon, and recommendations from various parties for improving them are clarified.

Case Study of Medium Voltage Motor Test Results

Abstract: A medium voltage motor was electrically tested at an industrial facility. The results of the test, and recommendations for action are discussed.

Case study of Medium Voltage Motor Trending

Abstract: Enhanced results are often obtainable if care is taken with record keeping of previous tests. Taking into consideration previous condition monitoring results is a vital step. In this case study, degradation was discovered, not by the results of the present test, but by comparing the results obtained against the entire test history.

Case study of shaft voltage and VFD Motor

Abstract: Repeated bearing failures were occurring, and EDE was called in to take shaft voltage measurements.

Case Study 2000kVA Generator aboard Research Vessel

Abstract: Temperature alarms were triggered on one of the two 2000KVA shaft generators aboard the vessel. After discussions, the decision was made to put into harbor for diagnostics.

The Role of Lightning Rods & Surge Arrestors in Electric Motor Protection

Abstract: This paper discusses the genesis of the Lightning Rod, as well as historical application of a variant called the Surge Arrestor. This is with particular emphasis for electric motors. Original works by IEEE from the early 1900's will be discussed, and compared against modern developments.

Hand Cranked Meg-Meter to battery Powered Megger®

Abstract: Insulation Testers come in many varieties. In this article, some of the history of the first Insulation Testers by Evershed and Vignoles Ltd will be covered, and then soome comparison between original techniques, and advanced, modern testers.


Measuring Reflected Voltage Spikes in VFD Motor Applications

Abstract: This article discusses the AC induction motor, when configured with modern adjustable speed/variable frequency drives. The article is focused on those that operate at or less than 600 volts. The widespread proliferation of adjustable speed/variable frequency drives has resulted in many process control improvements for industrial applications. These drives are generally used to very precisely control the rotational speed and direction of electric motors. In VFD applications, certain critical items such as cable length may not be allowed to vary, by the very nature of the plant, marine, or industrial layout. Therefore, testing for the existence of (and measurement of) these spikes typically requires deployment of an oscilloscope, with properly rated probes. An oscilloscope allows accurate measurement of any voltage spikes, and can help determine the effectiveness of any steps taken to mitigate them. 

 Micro ohms to Meg ohms

Abstract: This article discusses the difference between Micro-ohms and Meg ohms. It is important to understand the difference. Some meters are capable of making measurements across such a wide range, and care should be exercised to select the proper range when evaluating an electric machine. This article helps shed a little light on the basic subject.

Test Tip #4

A degraded stator like this one can be tested in various ways, don't forget you can usually core loss test the stator iron before you strip the coils. 

Test Tip #5
Eddy current braking systems are used in many applications. If you perform surge testing as a QC technique, perform both forward and reverse polarity tests.

Test Tip #2

Rotating fields can be drop tested, surge tested, or impedance tested. Regardless - short out the stator phase ends and open the diode bridge/slip rings for the test you select...

Test Tip #3

Large armatures like this one are often equalized or cross connected. This may make troubleshooting more complex. Contact EDE to learn how to work this out...

Test Tips

Test Tip #7
Many test facilities have multiple vendors test equipment on the same production line. Make sure they are calibrated regularly if you expect comparable test results!

Test Tip #1

Testing motors or generators in Storage:  An easy way to become proficient with electric motors testing equipment during normal operation....

Technical Articles/Case Studies

Test Tip #6
How can a motor have a single bearing? That is possible if the driven load - such as a reciprocating compressor acts as the 2nd bearing.