Smarter energy monitoring with predictive maintenance, IoT solutions

Advanced power measurement is in widespread use in controls engineering to save energy and classify machine behaviors by using predictive maintenance and Internet of Things (IoT) tools to reduce costs and boost operating efficiency of equipment.

By Sree Potluri, Beckhoff Automation July 7, 2018

Advanced power measurement is being used more frequently in controls engineering to tackle critical manufacturing challenges such as discovering ways to save energy, reducing peak loads, analyzing and classifying machine behaviors, and locating and dealing with energy hogs.

It also is used commonly to identify and track key energy usage statistics by tying them into predictive maintenance software and analyzing data using modern Internet of Things (IoT) tools to reduce costs and boost equipment efficiency.

Over the last two years, the industrial marketplace has seen a remarkable expansion in the availability of compact power monitoring technologies. A high percentage of these are not single-purpose, stand-alone devices. Instead, they are integrated into a standard input/output (I/O) platform. One way to accomplish this is by integrating the power monitoring electronics into a distributed I/O format—either in DIN-rail mounted terminals or machine mounted I/O modules.

This yields a number of immediate benefits, including a reduction in overall equipment footprint, streamlined I/O segments, shorter wiring and cable runs, faster commissioning, among others. In the context of PC-based control technology, these power monitoring solutions can be programmed in the same familiar software environment used for programmable logic controllers (PLCs), motion control, safety, robotics, and more, providing significant savings for engineers. 

EtherCAT in power monitoring applicationsI/O products based on the EtherCAT industrial Ethernet protocol offer particular advantages for power measurement and predictive maintenance applications. Depending on the application, it is important to determine what energy-related information is needed, such as voltage, power quality, and harmonics. Another consideration centers around IoT. Many engineers are looking for more information to implement predictive maintenance.

For such applications, entry-level measurement terminals with basic measurement features can be helpful. Every machine can have one low-cost terminal to measure voltage, current, and power, and send the data from an EtherCAT network to a local or cloud database. If plant personnel see changes in the measured value, they know exactly which machine needs maintenance based on the measurements and on diagnostic features in EtherCAT, which enable highly localized identification of time-based events in machines and equipment.

For applications where the need for power measurement is based on lowering the total production cost, a measurement terminal with more built-in features will be more helpful. There are 3-phase power measurement terminals with extended functionality that offer a wide range of additional features for mains analysis and energy management. Specifically, these can be used to measure harmonics, total harmonic distortion (THD), frequency, and power factor.

All measured currents and voltages are available as root-mean-square (RMS) values and the effective power and energy consumption for each phase can be calculated. The RMS values of voltage, U, and current, I, as well as the active power, P, apparent power, S, reactive power, Q, frequency, f, phase shift angle, cos φ, and harmonic are available to the user. Extended measurement terminals also can offer a very high measurement range, up to 690 V ac, 5A.

It is possible to monitor numerous channels simultaneously with a temporal resolution of up to 100 µs using the EtherCAT oversampling principle. Perhaps on the highest end of performance for I/O terminal-based power monitoring, compact variants are available that deliver an error maximum of 0.2% at 20 kilosamples per second (kSps) or 0.5% at 10 kSps. A standard PC-based control system has sufficient computing power for true RMS or performance calculation and complex custom algorithms based on the measured voltages and currents.

Through the oversampling principle, the I/O terminal can measure at shorter intervals than the cycle time of the control system. Also, by leveraging distributed clocks functionality, which is also inherent to the EtherCAT protocol, it is possible to measure power synchronously from numerous sources via other EtherCAT devices in the network. 

Power to the controls engineers

Software expansions designed to accommodate power monitoring in PC-based control systems also have elevated performance in system-integrated platforms. PLC libraries for the evaluation of raw current and voltage data can be supplied directly by power monitoring I/O terminals. Function blocks are available for the calculation of RMS values for current, voltage, and power.

These can be outputted as momentary or average values and maximum and minimum values are also available in the function blocks. Frequency and frequency spectra can be determined, such as harmonics in networks and their load in the form of total harmonic distortion (THD). All function blocks are available for single-phase and 3-phase systems.

Not long ago, this level of functionality and synchronization was reserved for complicated, expensive, and bulky "black box" devices that required their own programming software and existed inside a fairly closed ecosystem. This meant few machines could be afforded high levels of power monitoring technology for effective data analysis. Today it is possible to extract high-value power consumption data from all areas of a manufacturing environment from a control system fitted with the right I/O terminals. Controls engineers have more power to take energy monitoring into their own hands by adding compact I/O terminals with integrated measurement technology.

Sree Potluri, I/O application specialist, Beckhoff Automation. Edited by Chris Vavra, production editor, Control Engineering, CFE Media,


Keywords: I/O platform, energy monitoring, EtherCAT

  • Advanced power measurement can tackle many critical manufacturing challenges.
  • EtherCAT-based I/O products can provide special advantages for power measurement and predictive maintenance applications.
  • Software expansions in PC-based control systems have elevated performance in system-integrated platforms.

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