Jim Colby, Littelfuse, Inc
The Factories of the Future Will Demand Advanced Circuit Protection Technology to Keep Everything Connected
The original Industrial Revolution marked the transition from making things using human and animal power to making them with machines by harnessing water and steam power. The ability to use electricity in the mass production of goods made the second Industrial Revolution possible; the third came as the result of the use of computers to automate production processes. The fourth Industrial Revolution marks the transition from “dumb” machines (assembly lines, standalone automated painters, welders, etc.) to ones that are made smarter and self-configurable by incorporating sensors and processors and, more importantly, by connecting them together and to the operations center via the Industrial Internet of Things (IIoT). Sometimes known as Industry 4.0, it has the goal of making production more efficient, cost-effective, and flexible and to deliver a better product to the customer in less time.
However, the increased connectivity that the IIoT brings to factory automation systems also makes these systems particularly vulnerable to electrical damage from a variety of threats. These threats include electrostatic discharge (ESD), electrical fast transients (EFT), cable discharge events (CDE), lighting-induced surges, as well as system-induced voltage transients that occur when large motors turn on or off, etc. via both data and power connections (Industrial Ethernet, PoE, CAN bus, RS-485, Profibus/FieldBus, etc.). The engineers designing and implementing automation systems in industrial settings need to be aware of the appropriate circuit protection solutions, like TVS Diodes, TVS Diode Arrays, gas discharge tubes, and SIDACtor® protection thyristors, that can help reduce (or eliminate) the risks involved. This article offers an overview of circuit protection solutions that are particularly appropriate for a variety of industrial automation applications and the advantages they provide for ensuring the reliability of the systems driving the factories of the future.
Industrial Ethernet
Industrial Ethernet (IE) combines standard Ethernet protocols with rugged connectors and high temperature switches. Components used in industrial applications must be able to withstand temperature extremes, humidity, and vibration significantly beyond the ranges for equipment intended for installation in typical office environments.
Industrial Ethernet networks must interoperate with both current and legacy systems, and must provide predictable performance and maintainability. In addition to physical compatibility and low-level transport protocols, a practical industrial Ethernet system must also provide interoperability of higher levels of the OSI model. An industrial network must provide security both from intrusions from outside the plant, and from inadvertent or unauthorized use within the facility.
Figure 1 illustrates one approach to indoor long-haul data line (not PoE) protection against lightning-induced transients, ESD, EFT, CDE, and power faults that’s appropriate for use in a factory automation environment.
Some industrial Ethernet circuit protection applications pose even greater challenges, such as in facilities with multiple buildings with equipment and cabling located out of doors. Figure 2 shows a circuit protection scheme optimized for these applications involving severe outdoor exposure in environments with frequent electrical storms.
Power over Ethernet
Power over Ethernet (PoE) describes any of several standardized or ad-hoc systems that pass electrical power along with data on Ethernet cabling. This allows a single cable to provide both data connection and electrical power to a variety of devices like IP security cameras. Unlike the USB bus, which also powers devices over the data cables, PoE allows for extended cable lengths. Power may be carried on the same conductors as the data or on dedicated conductors in the same cable. In a PoE scheme, the device that receives the power is called the client device or Powered Device (PD) and the device supplying the power is the Power Sourcing Equipment (PSE). “Mode A” power is supplied over the “active” data pair found in 10BaseT or 100BaseTX interfaces. “Mode B” power is applied over the unused pair for 10BaseT and 100BaseT interfaces. For 1000BaseT and 10GbE applications, all wire pairs are used for data transfer, so there are no “spare pairs.” Figure 3 illustrates circuit protection schemes for PoE Powered Device and Power Supply Equipment.
CAN Bus (DeviceNet)
Industrial Ethernet and PoE are far from the only communication buses relied upon for factory automation system coordination. The CAN (Controller Area Network) Bus standard allows microcontrollers and devices to communicate with each other in applications without a host computer. Although not nearly as fast as Ethernet, CAN Bus is highly robust and capable of communicating data reliably over substantially longer distances than Ethernet. That makes it a good choice for applications that require communicating instructions or returning data from separate pieces of equipment located some distance from each other. Figure 4 shows a typical CAN Bus application example. The DeviceNet network is based on CAN bus technology.
RS-485 (Profibus, FieldBus)
Much like CAN Bus, RS-485 is highly robust and offers industrial users the ability to transmit data without degradation over longer distances, but it’s somewhat faster than CAN Bus. In industrial settings, it’s often used for control of lighting, security cameras and fire detection systems. Figure 5 illustrates one circuit protection solution for RS-485 ports subject to ESD or low-level transients due to lightning-induced surges. Figure 6 represents a higher level of protection.
Conclusion
To learn more about protecting Ethernet circuits and equipment in industrial settings from ESD, lightning, power faults and other electrical transient threats, download a free copy of the “Ethernet Protection Design Guide” from Littelfuse at http://www.littelfuse.com/~/media/Electronics/Design_Guides/ESD/Littelfuse_Ethernet_Protection_Design_Guide.pdf.pdf. For help in choosing an appropriate fuse or TVS Diode Array, visit https://littelfuse.transim.com/login.aspx? and sign up for a free Littelfuse iDesign account. The iDesign platform guides you through the process of choosing the best component for an application, finding parts documentation, sharing information with colleagues, and ordering part samples for prototyping.
Author
James Colby is Business Development Manager for the Electronics Business Unit of Littelfuse, Inc. His responsibilities include identifying and developing strategic growth markets as well as introducing new products into those markets. He received his BSEE from Southern Illinois University (Carbondale) and MBA from Keller Graduate School of Management (Schaumburg). He has been with Littelfuse for over 17 years and in the electronics industry for more than 25 years, and can be reached at jcolby@littelfuse.com.
