Power Systems

Maximize production efficiency with high-end power measurement

Machine-friendly input/output (I/O) hardware for high-end measurement technology continues to grow, optimizing power monitoring while eliminating harmonic distortion.
By Sree Potluri February 7, 2019
Figure 4: Different EtherCAT I/O modules provide a variety of system-integrated diagnostics, filters, scaling features and form factors. Courtesy: Beckhoff Automation

Over the past decade, power measurement technology has continued to advance—giving controls engineers many options. Black box technologies are no longer the only options for power monitoring. High-end measurement strategies exist as extensions of standard machine control platforms. System-integrated input/output (I/O) terminals gather data to be analyzed in the cloud or on a local PC and also perform power analysis on the hardware.

High-end measurement technology benefits

High-end measurement I/O modules provide cost-effective options to enhance each of the main energy measurement categories including power monitoring, power measurement, and maintenance. Because these I/O terminals are open, they help plants expand the range of power measurement data that can be gathered and analyzed.

Figure 1: The categories of high-end energy measurement I/O modules include power monitoring, power measurement, and maintenance. Courtesy: Beckhoff Automation

Figure 1: The categories of high-end energy measurement I/O modules include power monitoring, power measurement, and maintenance. Courtesy: Beckhoff Automation

Adding high-end power measurement technology to each machine and production line will allow engineers to optimize equipment performance, diagnose issues faster, and complete predictive maintenance as irregularities begin occurring, which increases plant uptime, efficiency, and profitability.

EtherCAT-enabled I/O modules for power monitoring offer sampling rates at a resolution of 50 µs, which is capable of monitoring any dynamic system. These modules also simplify power monitoring by providing values of three-phase voltage up to 690 Vac or 400 Vdc and currents up to 5 amps.

High-end power monitoring is used for grid analysis and monitoring incoming power. It is often used at the machine level and these modules can provide information necessary to correct harmonics in the power supply from the utility, which cause distortion and undesired results.

The combination of fast sample rates and application-specific capabilities leads to better and more actionable data insights. High-end power measurement modules help accomplish this through three key technologies along with the advantages PC-based control platforms provide.

Distributed clocks, oversampling, timestamps

Like other EtherCAT devices, high-end power measurement modules rely on distributed clocks, oversampling, and timestamps to provide high-precision data. These EtherCAT technologies work together to provide high sample rates with precise synchronization among all devices at less than 1µs.

  • Distributed clocks: The local clock in an EtherCAT device automatically and continuously synchronizes with all distributed clocks on a standard time base. This synchronization also compensates for different communication runtimes and minimizes the deviation between clocks to less than 100 nanoseconds. Distributed clocks enable minimum response time, deterministic actual value acquisition, and deterministic set value output. Local clocks also trigger oversampling functions within these high-end modules.
  • Oversampling: With built-in oversampling functionality, the EtherCAT measurement modules transmit process data to the controller more than once per communication cycle. Because higher resolution requires reduced cycle times, oversampling enables repeated sampling of process data by a set factor within a communication cycle. This supports, among other functions, fast signal monitoring within a dynamic machine control system, signal sampling independent of cycle time, and fast loop control. Even with moderate communication cycle times, sampling rates of 200 kHz are possible.
  • Timestamps: This technology applies specific timestamps to process data in addition to user information. As a result, it is possible to pinpoint the exact moment when energy spikes or other important events occur and to trigger precise outputs independent of the cycle time.

In addition to these three key technologies, EtherCAT I/O modules can provide a variety of system-integrated diagnostics, filters, scaling features, and form factors.

Figure 2: Evaluating harmonics and total harmonic distortion of voltages and currents is possible through high-end power measurement modules. Courtesy: Beckhoff Automation

Figure 2: Evaluating harmonics and total harmonic distortion of voltages and currents is possible through high-end power measurement modules. Courtesy: Beckhoff Automation

These technologies are even more effective when they’re combined with PC-based control. When using an industrial PC and automation software for machine control and monitoring, the process data acquired through high-end measurement modules can be further analyzed using existing software libraries on the machine.

In addition, the data is transmitted from the local controller to the cloud using common communication protocols such as message queuing telemetry transport (MQTT), OPC Unified Architecture (OPC UA) or advanced message queuing protocol (AMQP) to further analyze or compare the performance of individual machines against the entire line and plant. Further calculations can determine root-mean-square (RMS) values for voltage and current, minimum and maximum values, and the system’s harmonics.

Better monitoring and performance

Because they rely on distributed clocks, oversampling and timestamps, high-end power measurement modules are able to deliver significant benefits for machines and other applications. For example, modules feature zero crossing detection with a precision of 1µs using the distributed clock technology. This makes it possible to execute switching operations at zero crossing with high precision, which protects devices from in-rush current peaks.

Figure 3: Power monitoring I/O solutions provide values of three-phase voltage up to 690 V ac or 400 V dc and currents up to 5 amps. Courtesy: Beckhoff Automation

Figure 3: Power monitoring I/O solutions provide values of three-phase voltage up to 690 V ac or 400 V dc and currents up to 5 amps. Courtesy: Beckhoff Automation

These benefits also present advantages with harmonics, which can create undesirable results in machines. High-end power measurement modules integrate the evaluation of harmonics and total harmonic distortion (THD) of voltages and currents. The modules are also able to detect current and voltage peaks, imbalances, and residual current.

Power quality measurement, IoT devices

With all of the advances in the Internet of Things (IoT), low-cost maintenance modules can provide basic information about machines if high-end systems are not needed. Not only do these entry-level options give voltage values, but they also provide basic power quality analysis through the power quality factor.

For applications where harmonics values are not an issue, the power quality factor can identify issues with the system’s power supply. This can be very helpful in diagnosing issues, especially for machines that are sensitive to interference. Even machines that undergo rigorous testing during commissioning sometimes encounter issues when shipped to the customer site. The problem might stem from power quality, which is easy for these modules to detect.

Figure 4: Different EtherCAT I/O modules provide a variety of system-integrated diagnostics, filters, scaling features and form factors. Courtesy: Beckhoff Automation

Figure 4: Different EtherCAT I/O modules provide a variety of system-integrated diagnostics, filters, scaling features and form factors. Courtesy: Beckhoff Automation

Cross-system communication challenges and the more expensive black-box technology created a barrier to performing expansive power monitoring. However, newer modules are more affordable, and EtherCAT’s openness allows them to work in almost any system.

The increased efficiency and production delivered by high-end measurement, along with more affordable packages, gives the power for machine and plant optimization directly to the controls engineer.

Sree Potluri is an I/O product marketer from Beckhoff Automation. Edited by Emily Guenther, associate content manager, Control Engineering, CFE Media, eguenther@cfemedia.com.

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KEYWORDS: Power measurement, harmonics, EtherCAT

Eliminating harmonic distortion with high-end power measurement technology

Benefits of high-end measurement technology.

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Sree Potluri
Author Bio: I/O application specialist, Beckhoff Automation