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PdMA Tip of the Week

 

Show Me the Swirl

High pole pass frequency (Fp) peaks as a sideband around electrical line frequency or as an independent frequency in a current demodulated spectrum are both indications of a rotor bar defect. However, it is important to remember that mechanically induced load changes can also create frequency peaks at or near Fp that mirror the effects of a broken rotor bar. If a trend is not your friend, meaning you have not collected enough historical data to identify a trend, then you should always rely on a third indication before calling the rotor bad. One very good indication is to monitor the Swirl Effect. Best described in detail by the late Gerald Kliman, the Swirl Effect is the 180° reversal in phase of the air gap flux across a broken bar. This disturbance of flux is easily transferred to the stator and can be detected with current signature technology like the EMAX focusing on the 5th harmonic as a primary location for slip related sideband activity. So, if you’re trying to make a decision on a possible rotor defect, don’t forget the swirl.

To learn more about the Swirl Effect from a broken rotor bar Click Here to view a short video.

You are invited to submit an Electric Motor Testing Tip of your own and receive a free PdMA® mug or hat if we publish it! Contact Lou at lou@pdma.com.

 
 

Show Me the Swirl
October 27, 2014
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Why MCEMAX®?

Fault Zones
Power Circuit Fault Zone
Power Quality Fault Zone
Rotor Fault Zone
Stator Fault Zone
Air Gap Fault Zone
Insulation Fault Zone

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Quality Assurance

Insulation Case Study

 

PdMA® Corporation Releases MCEGold® 2.6.2
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2014 Training Schedule Posted
The PdMA® training schedule for 2013 has been posted.
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2012 Best Maintenance Reliability Program Winner
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The affordable MTAP3 offers the ability to safely capture data in many of the smallest enclosures where the MTAP2® cannot be installed.
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