What is electrical signature analysis (ESA)?

In the world of industrial maintenance and reliability, staying ahead of equipment failures is not just a goal—it’s a necessity. That’s where a condition-based maintenance (also known as predictive maintenance) approach, supported by condition monitoring techniques, is transforming the way industrial companies are predicting and preventing equipment failures. In the modern condition monitoring toolkit, there are 5 major technologies: vibration analysis, oil analysis, acoustic emission analysis, infrared thermography and electrical signature analysis (ESA). While many have heard and used vibration and oil analysis for decades, not many know about ESA. So, what is ESA, and where does it fit in the predictive maintenance toolkit?

The essence of ESA

Where other condition monitoring techniques analyze vibrations or oil or temperature, ESA analyzes the voltage and current being supplied to the motor driving the valve, pump or other equipment to accurately track the whole machine’s health. It’s based on the fact that subtle changes in a machine’s operation affect the connected motor’s magnetic field, which then affects the supply voltage and operating current. Using a variety of analytical techniques, ESA can provide a detailed picture of what’s going on across the entire drive train, from motor to transmission to load.

ESA vs. MCA: What sets them apart?

At its core, ESA is a close cousin to motor circuit analysis (MCA). However, there’s a crucial difference: ESA is performed while the machine is running (or “online”), while MCA is performed while the machine is deenergized (“offline”). As is evident from this description, only ESA can provide continuous insight into the machine’s condition.

The evolution from MCSA to ESA

There’s a dizzying array of electrical analysis methods out there. Probably you’ve encountered motor current signature analysis (MCSA), electrical signature analysis (ESA), power quality analysis and more.

But it all began with MCSA.

The journey from MCSA to ESA reflects a significant advancement in condition monitoring technologies. It began in the mid-1980s when the Oak Ridge National Laboratory (ORNL) embarked on a project at the behest of the US Nuclear Regulatory Commission [1]. The project’s aim was to explore methods for monitoring the aging and service wear of motor-operated valves in nuclear power plants, marking the inception of what we know today as MCSA.

MCSA: The foundation

MCSA emerged from ORNL’s efforts to harness information from the running current of motors—a method that offered the advantage of remote, non-intrusive data acquisition. This early work laid down several techniques under the MCSA umbrella capable of detecting damage and imminent failures in motors. MCSA’s ability to diagnose issues based on current analysis alone was groundbreaking, setting a precedent for future innovations in the field.

Transitioning to ESA

MCSA’s successful application set a foundation for ORNL to develop additional signal conditioning and analysis tools. In addition to analyzing electrical current, they added in voltage and power monitoring. This has resulted in a powerful suite of techniques, grouped under the term of electrical signature analysis (ESA). By integrating additional parameters like voltage alongside current, ESA offers a more detailed and holistic view of a machine’s health, enhancing the predictive maintenance capabilities of industries worldwide.

The technique has a long track record as you’ve just seen. Today, companies in diverse industries like water, wastewater, steel and oil & gas use ESA to reduce the risk of machine failure, improve reliability and efficiency, save energy and decrease costs.

The Advantages of ESA

Below are just a few key advantages of ESA over other condition monitoring techniques, which make it an irreplaceable and essential tool as part of the comprehensive maintenance toolkit.

Truly remote condition monitoring

ESA is different from all other condition monitoring techniques in that electrical sensors do not need to be near the actual machine. It uses current transformers and voltage taps that are installed in the motor control cabinet, where they capture all three phases of the current and the voltage at a high frequency around the clock. So, right there you have ESA’s first major advantage. It doesn’t matter whether your pump is submerged in wastewater or you’re running 2,000-degree molten steel over your rollers; ESA sensors are easy and safe to install, and they’re shielded from operational hazards.

Reliable failure detection technology

As the name suggests, ESA systems excel at detecting electrical faults as soon as they start to develop. Considering that roughly 30% of industrial motor failures are due to electrical faults, this is great news and a point where ESA really stands out. ESA systems will detect electrical faults earlier than any other condition monitoring technology. This includes broken rotor bars, bearing currents, stator faults and power quality issues. That’s because electrical changes directly affect the motor’s magnetic field. By measuring current and voltage, electrical signature analysis has direct access to the very first sign that damage is starting to occur.

However, it’s a common misconception that ESA can only catch electrical failures; it can detect and localize mechanical faults as well. For example, mechanical failures like misaligned coupling will cause vibrations that will influence the air gap between the motor’s stator and rotor, causing the magnetic field disturbances, and in turn, affecting the supply voltage and operating current.

Additional insights into asset performance and energy efficiency

Beyond failure detection capabilities, ESA-based systems can track and offer a host of additional insights such as a real-time pump performance curve and energy efficiency metrics. All these metrics require current and voltage data, making it unique to ESA systems.

• Real-time pump performance curve: The pump affinity laws enable ESA technology to transform its current and voltage measurements into accurate estimates of real-time power, head and flow. This allows such systems to plot a pump’s operation relative to its best efficiency point in real time. These insights can help you steer a pump back to its best efficiency point, reducing cavitation and raising bearing and seal life. Over time, the data can tell you where redesign or replacement would score major cost and efficiency gains.
• Energy efficiency insights: ESA systems can use the current and voltage data being drawn from the system to track a machine’s actual efficiency from one moment to the next. You can use these insights to implement both short-term, quick and low-cost changes like resizing the pump, and also make long-term decisions such as upgrading the pump for a more efficient class.

It’s good to note here that even though only ESA systems will have the necessary data to calculate all these extra insights, it does go beyond fault detection monitoring. So, not every ESA vendor will provide all of the capabilities.

ESA in the 21st Century

As industries evolve toward smarter and more efficient operations, the role of ESA in proactive maintenance strategies has never been more critical. It’s not just about preventing unplanned downtime anymore; it’s about leveraging asset health and performance data to make informed and timely decisions that enhance the reliability and performance of critical industrial assets. 21st-century ESA systems embody this shift, providing additional important information through which maintenance teams can foresee and proactively act to keep their assets running more efficiently, for longer.

References

[1] “Electrical Signature Analysis (ESA) for Condition Monitoring & Condition based Maintenance” by Oak Ridge National Laboratory (2001)