Electric motor test equipment is often used to identify whether the root cause of a system anomaly is electrical such as a Power Quality, Power Circuit, Insulation, Stator, Rotor or Air Gap Fault. And, after all the analysis is complete and the source of the anomaly is not from any of the classic electrical Fault Zones, what next? Rather than stopping and exclaiming “It’s Not the Motor!”, the same electric motor test equipment can perform Current Demodulation, which allows the analyst to identify machine train related frequencies like belts and pulleys, fan blades, pump vanes, gear related frequencies and more. Once the frequencies identified in the demodulation spectrum are confirmed, you should establish a visible band alarm around the frequency peak with a caution and severe setpoint to alert the end user if the amplitude of the identified machine train frequency reaches a predetermined alarm value. Confirming the machine train frequencies can be done through mathematical calculations with basic knowledge of the system or another popular method is to just ask the vibration team. Often the vibration team has already broken out the calculator and could easily help you identify the source of the peaks you are seeing. As an example, in a gear box failure the secondary shaft frequency of a reduction gear was seen in the Current Demodulation Spectrum and once confirmed was used to identify damaged gear teeth early enough to prevent an unplanned outage.
For more details on the gear box failure and many other machine train calculations visit the PdMA Website to listen to the Todd and Noah Show Podcast focusing on using current demodulation to identify mechanical anomalies. https://pdma.com/podcasts/
