Industrial Motor Monitoring | Dynamic Ratings

Why Should I Monitor My Industrial Motor?

It is important for industrial plants to have reliable motors. The key benefits to implementing industrial motor monitoring are

  • Increasing safety for workers
  • Reducing unexpected failures to increase plant reliability
  • Reducing unplanned outages which saves time and money

Online condition-based monitoring collects data generated during the assets normal operating conditions to get real-time awareness of problems.

Industrial Induction Motors

Failure Modes of Industrial Motors

What causes failure in a motor's stator windings?

Syncronous Motor

Failures in stator windings usually occur due to four factors

  • high temperatures
  • high electric stress
  • inadequate ambient conditions around the windings
  • mechanical issues

All of these failures have the potential to generate partial discharge (PD) and influence the life expectancy of the winding. Consequently, the rate of deterioration in stator winding insulation can be tracked by measuring partial discharge activity and closely monitoring PD tendencies.

Manual Inspection vs Online Monitoring

The condition of industrial motors is usually determined through periodic manual inspections during an outage. These inspections look for obvious problems such as physical damage, frayed connectors, degraded insulation and evidence of overheated components. The disadvantage of periodic inspections is that the time interval between two maintenance activities is not always sufficient to identify developing issues prior to failure. Periodic maintenance is often performed when the asset is not in service or the plant is in outage and the actual state of the asset with respect to time and plant operation condition is often not available for diagnosis. Periodic maintenance frequently results in the maintenance of healthy assets, increasing maintenance costs, and the possibility of human error.

Online Monitoring for Industrial Motors

There are two things to consider when implementing online PD monitoring for motors:

Noise Cancellation

Signal Noises from outside the motor must be eliminated. Noise can allow misinterpretation of the data or no interpretation. There are many techniques for noise cancellation, you can read more about them in this white paper.

Signal Attenuation

Sensors used for detecting deterioration signals need to have good sensitivity and coverage. Coupling capacitors installed at the line terminal of a machine only have a zone of 10-15% sensitivity of the total winding. Learn more about signal attenuation in this white paper.


According to IEEE, 20% of motors are taken out of service within 12 months of maintenance due to forced outages.


15% of a motor is being monitored for PD (maybe 2-3 coils). The rest is outside of the coupling capacitor zone.


Most motors have at least 6-12 RTDs already inside which can be used to transmit PD pulse data.

Use Realtime Data with Motor Monitoring

Rotating Machine Monitor

Rotating Machine Monitor

The Rotating Machine Monitor is a continuous partial discharge monitor that monitors, stores, and correlates operating dynamics. The RMM provides information as to the health of the stator winding insulation in medium and high voltage motors and generators.


Coupling Capacitor

Coupling Capacitor Sensor

The Coupling Capacitor is a highly sensitive partial discharge (PD) sensor used to decouple PD from the monitored conductor. Install Coupling Capacitors as close to the winding as possible for maximum sensitivity.


RTD-PD Sensor

RTD-PD Module

The RTD-PD Module detects PD that occurs deep within the windings. Line-side coupling capacitors only identify PD levels close to the equipment terminals. Use RTD-PD sensors to allows a more comprehensive view of the true condition of the machine’s insulation system.


Comprehensive Partial Discharge Monitoring Approach

Generation Site

It is important to consider a comprehensive partial discharge monitoring approach. PD can occur in generators, isolated bus ducts, step up transformers, and switchgear. Comprehensive monitoring of the entire power train can greatly increase the ability to pinpoint problem locations. To learn more about comprehensive PD Monitoring, visit our overview page.


Additional Resources


A Decade of Experience of Proactive Maintenance of Power Generation Assets


Continuous PD Monitoring for Motors and Generators


Success Story of PD Monitoring at a Generation Power Plant.