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Choosing a Gas Discharge Tube for Surge Protection

Posted on June 15, 2022 Michael Rodriguez Aircraft Parts

Power surges are common events that may occur over 50 times a day in a given power system. While the vast majority of these surges are minor and do not pose any threats to devices, those which are greater in magnitude may cause serious damage or even complete destruction to associated electronics. To help attenuate the impact caused by transient overvoltage, distributors and end-users implement surge protection into their systems. Surge protection is facilitated by specialized components called surge protection devices, or SPD. SPDs are designed to limit the voltage reaching an electronic device by blocking or shorting the current. Such strategies may be met by the use of inductors, metal-oxide varistors, spark gaps, or gas discharge tubes. In this blog, we will focus on gas discharge tubes and what factors must be considered when deciding upon one.

Although most DC systems rely upon bypass capacitors and series inductors for surge protection, these devices only perform optimally within a narrow low-voltage window. As such, a transient high voltage event is likely to overcome the natural response time of these components, thereby not providing adequate protection. Gas discharge tubes, on the other hand, remain efficacious even when exposed to extremely high voltage levels.

Gas discharge tubes are devices containing a dielectric gas, such as atmospheric air or dry nitrogen. These gases are unique in that they are inert and effectively prevent electrical charges from passing through them. Although there are over a dozen options for the material used inside a gas discharge tube, each element or compound exhibits strong dielectric strength, thermal stability over a broad range of temperatures, and non-flammability. For all gases, several factors may bolster or attenuate their dielectric strength, including density, pressure, and moisture. As such, moisture analysis tools are commonly used in high-reliability applications, as well as pressure gauges. Another limitation and factor to consider is the altitude at which the device will be operating since lower atmospheric pressure may hinder or inhibit functionality.

When choosing a gas discharge tube, one of the crucial features to look at is capacitance. In general, the device's capacitance is inversely proportional to the efficacy of the discharge tube. Next, it is necessary to determine the sparkover voltage, which is the salient and defining feature of the gas discharge tube. This value, which represents the voltage at which breakdown will occur, is determined by the gas being used, the spacing of the electrodes, as well as the pressure and moisture of the operating environment. Although the sparkover voltage determines the absolute maximum voltage for the device, it is also important to consider the holdover voltage, which defines the optimal and safe operating voltage range.

In addition to the inherent performance metrics of a gas discharge tube, customers should also be aware of the different package and connector types in order to ensure the device can be appropriately integrated with the target system. For board-level applications, gas discharge tubes typically come in the integrated circuit (IC) moiety, although several manufacturers have begun integrating gas discharge tubes with surface mount technology (SMT).

When you are in need of high-quality gas discharge tubes for your surge protection applications, there is no better alternative to ASAP Parts Unlimited. As a subsidiary of ASAP Semiconductor, we offer a vast selection of over 2 billion ready-to-purchase items for the aerospace and electronics industries. Our team of experts remain at our customers' disposal 24/7x365, and are enthusiastic about providing you with a competitive quote at any time. To get started, simply fill out an Instant RFQ form as found on our website, and you will be provided with a customized solution within 15 minutes or less.

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