October 24, 2019
The global need for and use of surge protective devices (SPDs) continues to grow, and the need for certification and testing of SPDs is also increasing. This growth in use is due to the substantial rise in alternative energy applications, including wind and solar, requiring surge protection; the increased demand for protection of electronic devices, such as LED lighting and information technology equipment; and mandates/code requirements for protection of critical systems. The use of SPDs is intended to safeguard expensive electrical equipment from electrical surges, improve power quality, and reduce downtime. As technology evolves and the value of various different devices increases, the demand for appropriate SPDs increases, as well.
To meet these mounting demands, SPD manufacturers are often challenged with designing new SPDs intended to meet the unique needs of the expanding market. These new SPD designs must then be tested and certified for compliance with appropriate requirements. Depending upon the construction, specifications and design of your SPD, the certification of your new devices can become both time consuming and costly. However, it is possible to reduce time to market and control costs. The following three simple SPD design considerations can help you be better prepared when it comes time to certify your product.
1. Use symmetrical construction in your designs
Maintaining design consistency can help streamline the design process and ease the certification process. More specifically, designing a product that allows for representative testing reduces the number of samples required, reducing time to market and lowering testing costs. Symmetrical construction is a repetitive or duplicative design and can be achieved in several ways, including:
- Using identical or similar component and layouts for each mode on printed wiring board
- Using modular type SPDs where the same modular type SPD is used for each mode
- Using DIN rail type SPDs where the same DIN rail type SPD is used for each phase/mode
To allow for representative testing, it is also helpful to limit the number of different voltage surge components used in a series and the use of alternate components in unproven constructions to only what is absolutely necessary. Variations in either area can increase the number of required samples and tests, both of which can increase costs.
2. Use proven, certified components
Design with certified components whenever possible. In addition to offering you an extra level of confidence, using proven components can reduce the need for testing in the end-use application. Look for UL Listed or Recognized Components and, for the latter, consider the component’s unique Conditions of Acceptability in your design.
Using Type 1CA and 2CA Components or Listed Open Type SPDs (in North American applications)
that already comply with the applicable requirements reduces testing to only those requirements affected by your end product. For International Electrotechnical Commission (IEC) applications, use components with Marks of conformity to the appropriate standard when possible.
3. Understand overcurrent protection (OCP) needs
Depending upon the construction and intended application of the SPD, an internal and/or external OCP may be required. Generally, an internal OCP is provided and an external OCP is specified in the installation instructions. When designing an SPD with an OCP, manufacturers need to consider surge current capability and compliance with other testing requirements. Both the OCP and the SPD must:
- Handle the surge testing without the OCP opening
- Withstand the withstand/fault test current until the OCP open
- Comply with the overcurrent, overload and bonding impedance tests based upon the rating of the OCP
If the above items are not considered during product design, compliance with all applicable testing requirements could become a challenge. For two-port SPDs (North America), the ampere rating of OCP devices shall not be less than 125% of the SPD ampere rating. A general overview of other testing requirements is as follows:
Surge testing: Will be conducted representative of internally provided OCPs and specified external OCPs. If an OCP opens during surge testing, this event will be considered a noncompliance.
Withstand/fault current testing: The OCP must open for the SPD to comply with the testing. Failure to open is a noncompliance. The only exception to this requirement is if the end product can withstand the test current for three cycles (this is uncommon).
Overcurrent, overload and bonding impedance tests: The current levels and time duration for these tests are based upon the OCP current rating. The tests are conducted without an OCP device.
The one commonality between these three tips is that they focus on the earliest phases of the design process. The best way to prepare for market access into your target markets is to begin planning for – and designing for – these challenges as early as possible, and engaging with a respected third party, such as UL, can help significantly.
Streamline SPD market access
UL’s nonprofit organization developed and continues to support UL 1449, the Standard for Surge Protective Devices. For more than 30 years, our business solutions organization has been the premier surge testing and certification company and is a Certification Body (CB) Testing Laboratory (CBTL) for IEC 61643-11, the standard for low-voltage surge protective devices. This background allows us to work with manufacturers to help them understand what is needed to comply with certification requirements based upon the intended user’s application/market. UL’s experts educate you on the anticipated testing required and can help conduct pretesting for research purposes or to determine if a specific design will work.
Specifically, for SPDs, we can also help you understand and consider spacings, power concerns, isolation requirements in the design phase and overcurrent protection requirements, which can reduce the need for costly redesign and special production of modified samples. To further simplify the process, UL provides all these certification and testing services under one roof. We are the only certifier that can offer you both a UL Mark and a CB Certificate for SPDs, and our custom-tailored approach allows you to take advantage of UL’s wealth of knowledge surrounding both North American and IEC requirements.
New surge generator helps reduce testing time
To continue supporting our clients, UL also added new surge testing equipment in our Melville, New York, facility. The equipment includes an impulse current surge generator capable of superimposing a 60 kiloamperes (kA) in (8/20) nominal discharge current through a device under test and energized surge testing with up to 1,000 volts (V) alternating current (AC) and 1,500 V direct current (DC). This increased testing capability and capacity allows for local surge testing of most surge protective devices to applicable U.S., Canadian and IEC surge protective device standards, including AC, DC and photovoltaic (PV) SPDs. As a result, UL can decrease testing times, offer more testing options, and allow clients to streamline all of their surge testing. So, you can get to market more quickly and focus on innovating for the future.
To learn more about the growing importance of SPD reliability and how UL can help you from the earliest design phases through testing and certification, contact UL today at [email protected] or visit UL.com/SPD.