Online or Offline Motor Testing – Which is Right for You?

by | Mar 21, 2019 | Motor Circuit Analysis, Motor Testing, Predictive Maintenance

You might think of your operation like a NASCAR car—a complicated system with lots of moving parts. Among the most important? The motor.

In addition, what is true of that car is true for your equipment as well. Motor testing should be a significant part of your predictive maintenance (PdM) plan because it provides critical information about the condition of your facility’s motors—info that might be hard to get otherwise.

If you want to avoid unnecessary pit stops for repairs, you want to get a motor testing program in place.

There are a couple of ways to go. Maybe you want an online (dynamic) program. On the other hand, maybe an offline (static) motor testing program is right for you. Ideally, you might incorporate both into your PdM program.

Online motor testing includes voltage level, voltage imbalance, voltage distortion, service factor, overcurrent, efficiency, rotor bar, operating point, torque ripple, load history, haystack, and operation condition tests. All of that boils down to determining the overall health of the motor relative to the running conditions of its environment. Correcting power quality or voltage issues can prolong the life of your equipment by reducing stress on the motor’s insulation.  Online testing is one of the only ways to verify whether rotor bars are broken or cracked.

Offline motor testing includes winding resistance balance, insulation resistance (IR/MegOhm), polarization index (PI), DC high potential (Step-Voltage/HiPot), and surge testing. Once the insulation around the windings weaken, a short will likely occur—and those shorts are the cause of most motor failures. Surge testing is the only way to detect turn-to-turn, phase-to-phase, and coil-to-coil insulation problems. Offline testing can identify dead shorts, imbalances between phases, poor connections, and weak ground wall insulation.

In the end, you want to make sure you are collecting pertinent motor data and that you understand the significance of that data. Properly interpreting the data from your motor testing protocol will help you make the right decision every time.

You would not send a racecar out on the track blind of potential problems with the motor. Make sure your facility’s motors are always ready to provide peak performance. ATS would love to be your pit crew, making sure your PdM program puts your business in the winner’s circle.


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