Archives for 2017

When performing offline (MCE) testing from the Motor Control Center (MCC) it is important to remember the resistance of the cable run is measured along with the stator winding. If there is a resistive imbalance it can be caused by the circuit and/or the windings. To find the “real” imbalance of the motor windings take another test at the motor terminals, thus eliminating the circuit. If the imbalance is in fact caused by the windings, then it will show up as a higher imbalance than when tested from the MCC. For example, a test from the MCC with three resistance readings of .1700, .1600, and .1755 will give us a 5.2% imbalance. After taking a perfectly balanced cable run out of the measurement, and testing from the motor leads, we would get .0700, .0600, and .0750 which will give us a 12.2%.

In summary, when confronted with a resistive imbalance from the MCC, it is important to perform further testing before identifying the motor as the faulty component.

To learn more about resistive imbalance view our MCEMAX Fault Zone – Power Circuit case study that can be found on our website
(http://www.pdma.com/webinars/Power_Circuit_Fault_Zone/powercircuit.html)or YouTube channel (https://www.youtube.com/watch?v=F4vrpo7DZRs).

Decatur Industrial Electric regularly has many customers visit our shop to look at the work being done on their equipment.

Pictured below is a customer visiting with employee Ken Norris and inspecting their 2,000 HP synchronous motor. We performed maintenance, re-insulation, and replaced controls.

Counterfeit bearings use another brand’s name when that brand didn’t make it.

Between fiscal year 2012 and fiscal year 2016, U.S. Customs and Border Protection has seized counterfeit bearing products through numerous entry ports. The World Bearing Association (WBA) and individual members of the WBA raided suspected Chinese facilities and found MILLIONS of counterfeit products since 2009.

Counterfeits are found in all sectors and detection is difficult.

• Counterfeiters are getting better
• Authentication is becoming more challenging

However, each authentic brand has unique overt/covert features and brand owners have designated experts assigned to authentication. ALWAYS contact the manufacturer.  The best way to safeguard product authenticity is to source products through authorized sources. To watch a presentation on this subject, click here. 

You have heard us many times discussing the effectiveness of an In-Rush/Start-Up test as a critical piece of information in assessing a variety of potential anomalies in components such as the stator, rotor, power, and load. Capturing the In-Rush/Start-Up during the start of an electric motor allows the capture of data when the motor is under extreme stress and more likely to expose anomalies.

Less often discussed is that the In-Rush/Start-Up test can also be instrumental in identifying mechanical and load related defects during routine scheduled testing. The enveloping feature of the In-Rush/Start-Up test taken during steady state gives a direct look into the load fluctuations of the motor being tested. Having a baseline of the expected load characteristics for a motor provides a very easy comparison for early identification of even subtle changes in these load characteristics which could be early indications of developing faults.

To view examples of these tests and see them successfully applied in the identification of a developing pump failure visit our website case study at:  http://www.pdma.com/webinars/Pump_Case_Study/Pump_Case_Study.mp4