Circuit Protection for Industrial Applications

As featured in Power Systems Design Magazine

Author: Alfredo Ochoa, Product and Applications Engineering Manager, and Sudesh Nayak, Manager, New Product Development, ProTek Devices

Industrial applications where humans or the environment directly interface with it is susceptible to current and voltage surges Industrial applications today face a serious challenge from improper circuit protection, costing money and lost time. Also, a negative brand image is often tied to system down time. Companies are better served, in terms of real dollars and perceived brand image, by avoiding product recalls. Proper circuit protection is one way to ensure this.

Any industrial application where humans or the environment directly interface with it is susceptible to current and voltage surges. So, these applications would need circuit protection. The common ones include point of sale (PoS) systems that have card readers, modems and serial ports or residential and commercial energy meters and smart meters, industrial displays, appliances, general control systems, instrumentation, photovoltaic systems, LED lighting, and many more. Any of these industrial applications are at an inherent risk from transient electrical threats that can include electrostatic discharges (ESD), electrical fast transients (EFT), surges, lightning or improper wiring.

Industrial Communications Systems

Communications systems are ubiquitous in industrial applications. For example, there is widespread use of RS-485, USB2.0, ProfiNet or ProfiBus setups. Traditionally a capacitor was used to protect these data buses from spurious fast transients such as ESD and EFT. However, data rates nowadays are steadily rising to a point where the capacitance can cause significant packet losses. A solution to remedy this would be a transient voltage suppressor diode (TVS diode).

A TVS diode is designed to act only at or above a voltage exceeding its minimum breakdown voltage (BVmin). Each TVS is rated for a stand-off or working voltage (VSW) which is well under its minimum breakdown voltage. Once the voltage across the TVS exceeds the breakdown voltage, it offers a low impedance path to the circuit ground. Thus, in an instance of transient overvoltage, the line that is protected by the TVS is clamped at a voltage closer to the working voltage of the application. A TVS is usually connected line-line or line-circuit ground. The advantages that a TVS provides are a noticeable reduction in capacitance and increased repeatability in terms of surge protection. Read more.