How to Choose a Generator for IEC 61000

How to Choose a Generator for IEC 61000
Hey, Jamison from ATEC here! I'm an electrical engineer and the V.P. of ATEC, and we get a lot of questions about how to choose an IEC 61000 generator. Today we will be covering the main requirements as well as some of the test specifics and capabilities of popular generators. So let's get into it!

There are three main things to consider:
  1. The test standards required
  2. Device Under Test (DUT) requirements
  3. Pre-compliance vs compliance testing
Though there are certain pros and cons with each type of generator available on the market, most will be able to accomplish your test. 

Test Standards for Transient Generators

Numerous test standards specify the transient immunity of devices, such as IEC, MIL-STD, ISO, and others. Determining the susceptibility of transients to your device is defined by the environment and probability of high-power electrical impulse. 

Let’s look at a few of the main commercial transient requirements from IEC, including IEC 61000-4-5.
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Table 1: Test Levels for IEC 61000-4-5 Combination Wave Testing

These test levels specify amplitude of the electrical transients required to be applied to your DUT. This becomes one of the main specifications to consider when choosing a transient generator. Depending on your device requirements this will be easy to pick, but will future requirements require more stringent testing or over-testing?  

We can compare the specifications of the most popular models to see what capabilities are available.
Table 2: Comparison of Transient Generator Capabilities

These generators all provide similar features and will all meet the test requirements for IEC 61000. Some have further capability and expandability for other sections of this standard. The important thing to note is the higher voltage outputs for EFT, surge, and ring wave on some generators, which is great for over-testing your product.

Device Under Test Requirements

Most electronic devices we come across are either powered by 120 VAC or DC from a battery. However, some require higher voltage, whether a 3-phase electrical motor or a high voltage battery pack. This is where configuring your transient generator becomes more complex, through the CDN requirements.  

What is a Coupling Decoupling Network?

A coupling decoupling network, or CDN, is used to isolate your device for a controlled testing environment. It allows for the application of specific transient waveforms to affect only the device under test and not the auxiliary equipment connected to it. 

Some CDNs are also built specifically for data lines including 2-wire, 4-wire, and ethernet-type coupling for both symmetrical and asymmetrical data transmission. As for power line CDNs, most transient generators include a 240 VAC/16 A internal CDNs, but there are many external CDNs that can increase current and power capability provided to the DUT. Most commonly current limits cap at 32 A/63 A/125 A and beyond, which is also specified within the same IEC 61000 standards.
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Table 3: Specifications of CDNs for IEC 61000-4-5 Surge Waveform

CDN specifications require that the CDN is designed to reproduce the waveform from the surge generator. When higher current DUTs are being tested, the design of the CDN allows for a slower pulse duration. We will look at some options available for higher current and data line CDNs needed for testing unique devices.
Table 4: Comparison of Power Line CDNs for Surge, Ring Wave, and EFT Testing
Table 5: Comparison of Transient CDN Capabilities for Data Line Testing

One thing to note is that automatic CDNs are only compatible with generators of the same brand, that are designed to communicate with the CDN. This enables synchronization of the pulse onto the power or data line. There are many advantages to having an automatic CDN compared to a manual CDN, such as ease of use, minimal changes to test setup, and more capabilities for automating.

A manual CDN requires the coupling path to be manually selected via connectors. Synchronization is possible with the addition of an automatic CDN for timing. The main advantage of a manual CDN is that it can be configured to work with any manufacturer of a transient generator.

There are many options available for a variety of requirements. Picking what conducted immunity test equipment to use can be narrowed down. 

Pre-Compliance vs Compliance Testing

Performing pre-compliance tests during the R&D phase is always a good idea. Depending on product roadmaps, the main consideration for getting this essential product development testing done is: 

To Buy or To Rent

Read more about the benefits of renting. But in short, if only 1 to 2 products are being developed a year that require testing, renting will likely be the most cost effective. If testing requirements are needed throughout the year, once a month at least, then purchasing is an option to consider.  

Risk is the other critical consideration. If testing is held off on until going to a test lab for certification, the risk of failing is increased without pre-compliance testing. Delays are caused when a product fails in the lab, requiring redesign and development time to be stretched out. Things which are easily resolved when pre-compliance testing is performed throughout the development process. Learn more about the process of EMC testing.

Also see ATEC's eBay store for used transient generators to purchase for pre-compliance testing.

What is Compliance Testing? 

A full compliance test encompasses many more requirements than the pre-compliance test. This includes more specifications in the test setups and environments. The biggest significance is the calibration process of the test equipment and data taken during testing, which takes into account the uncertainties of the measurements. 

It is easy to find a test lab that will offer full compliance testing and ensuring that pre-compliant testing has been performed throughout your development process will ensure success.

For questions about IEC 61000 generators, ATEC is happy to help out. Our wide inventory of EMC test equipment includes everything to complete either pre-compliance or full compliance, and our ATEC Assurance policy means risk-free renting. Reach out for a quote today.