When I first started out in the switches and disconnectors industry 12 years ago, I thought the hardest part of our job was crafting a reliable, long-lasting product that could stand up to the harsh conditions our clients throw at it. Early on, I learned that durability only goes so far—if a switch or disconnector can’t work alongside other electronic gear without causing chaos, it’s pretty much useless in today’s connected world. That’s where electromagnetic compatibility (EMC) testing comes in, and over the years, I’ve worked with my team to refine every step of this process, because we know that skipping corners here isn’t just a mistake—it’s a risk our clients can’t afford. Switches & Disconnectors
Most of our clients come to us from sectors like renewable energy, industrial automation, and power distribution, where a single EMC failure can shut down an entire operation. I’ll never forget the time a wind farm client called us in a panic—their new switchgear was interfering with the control systems on their turbines, causing unexpected shutdowns that cost them tens of thousands of dollars in lost energy production before they even got the project fully online. We fixed the issue for them, but that experience stuck with me: EMC testing isn’t just a box to tick for compliance—it’s how we prove our products will keep their operations running smoothly, no matter what other electronics are nearby.
So, how do we approach EMC testing for our switches and disconnectors? Let me walk you through our process, step by step, because it’s not just about following standards—it’s about tailoring every test to the specific product and the environment it’s going to live in.
First, we start with pre-test analysis and documentation. Before we even set up any test equipment, we pull every spec we have for the product: its voltage and current ratings, the type of load it’s designed to switch, the enclosure material, its internal circuitry, and even its mounting configuration. For example, a high-voltage disconnector for a solar farm has very different EMC needs than a low-voltage switch used in a food processing plant’s control cabinet. We also review the relevant standards for the client’s region and industry. In the EU, that’s usually EN 61000 series, while in North America it’s IEC 61000 and FCC Part 15 for industrial products. We make sure we’re not just checking the minimum requirements—we build in extra margins because our clients operate in real-world conditions that are never as controlled as a lab.
Next, we set up our test lab properly. EMC testing is all about controlling variables, so our lab is shielded with conductive walls to block external electromagnetic interference (EMI) from skewing results. We use test tables that are either non-conductive (for low-level products) or conductive ground planes (for high-voltage gear) depending on what we’re testing. For switches and disconnectors, which often handle large currents, we pay special attention to cabling. We use the same type of cable the product will use in the field, routed the same way, because even small changes in cable length or routing can drastically alter EMC performance. We also mount the product as close to its final intended setup as possible—we’ve seen too many products pass tests on a test bench only to fail in the field because they were mounted wrong, so we avoid that mistake from the start.
Once the setup is ready, we move on to radiated emission testing. This measures how much electromagnetic energy our product sends out into the surrounding space. For our switches, which toggle large loads, the switching action generates a lot of transient signals—spikes that can interfere with nearby radios, communication systems, or other sensitive electronics. We use calibrated antennas that sweep across the frequency range relevant to our client’s industry, from 30 MHz to 1 GHz for most industrial products, and up to 18 GHz for higher-frequency applications. For example, a switch used in a smart grid has to meet stricter radiated emission limits because it communicates with other grid components wirelessly. We log every reading, and if we find a frequency that’s over the limit, we don’t just tweak the product and retest—we track down the source of the emission. It might be unshielded internal wiring, a lack of grounding, or even the way the switch’s contacts arc when they open or close. Last year, we worked on a medium-voltage disconnector where the arc across the contacts was emitting a signal at 450 MHz that was interfering with a client’s SCADA system. We solved it by adding a small arc suppression diode and a shielded terminal block, and we re-tested to confirm the signal was gone.
The other side of radiated testing is radiated immunity testing. This is where we expose our product to external EMI to make sure it still works correctly. In real life, a switch or disconnector might be near a radio tower, a welding machine, or even a lightning strike—all of which create strong electromagnetic fields. We use a signal generator and a power amplifier to create those fields in our lab, then test the product’s functionality before, during, and after exposure. For our disconnectors, which are often located outdoors in remote areas, we test at field strengths up to 10 V/m, which is higher than the minimum required by standards, because we know remote locations have less protection from external interference. We’ve had a client test a competitor’s switch that failed this test—when exposed to a strong field, it would randomly toggle on and off. Our product passed with flying colors because we added filtered inputs to the control circuitry that ignore stray EMI signals.
Next, we do conducted emission and immunity testing, which focus on the power and control cables connected to the product. Radiated emissions don’t tell the whole story—EMI can also travel along the cables leading to and from the switch or disconnector, interfering with other devices plugged into the same power line. For conducted emission testing, we use a line impedance stabilization network (LISN) to separate the product’s signals from the main power grid, then measure the noise on the cables. For immunity testing, we inject test signals directly into those cables to simulate EMI coming through the power line or control wires. For example, a low-voltage switch used in a factory might have control wires running next to a high-voltage motor cable—we test that setup by injecting noise into the control wires to make sure the switch doesn’t respond incorrectly. We also test for fast transients, which are the sharp voltage spikes from switching large loads, and surges, which simulate lightning strikes or utility switching events. These spikes can damage internal circuitry if the product isn’t properly protected, so we use surge generators to apply 1 kV to 4 kV surges (depending on the product rating) and check that the switch still operates correctly without any damage.
One part of EMC testing that’s often overlooked, especially for switches and disconnectors, is transient susceptibility from the switching arc itself. When a switch or disconnector opens or closes, the arc between the contacts creates a strong, short-lived electromagnetic pulse (EMP) that can interfere with the product’s own control system or nearby electronics. We test this by triggering the product’s switching action multiple times in our lab, monitoring both the product’s internal circuitry and any connected sensors or control devices. Last quarter, we had a customer in the mining industry whose switch was causing their proximity sensors to trigger randomly every time the switch turned on a conveyor belt. After testing, we found the arc from the switch contacts was generating an EMP that was coupling into the sensor wiring. We fixed it by adding a shielded cable for the sensor and a common-mode choke, and the problem was gone.
After all these tests, we don’t just hand over a report that says “passed” or “failed.” We provide our clients with a detailed breakdown of every test we ran, every reading we took, and any modifications we made to the product to meet the requirements. We also do field testing whenever possible—when a client lets us install our product in their actual working environment, we monitor it for weeks to make sure it performs as well in real life as it did in our lab. For our renewable energy clients, that means installing test switches on their solar or wind farms and monitoring their performance during different weather conditions, from extreme heat to heavy rain, because we know environment can affect EMC performance too.
I’ll be honest, EMC testing isn’t cheap, and it takes time—we might run 20+ different tests for a single product, and each one requires careful calibration and experienced technicians to run. But we never cut corners here. Our clients rely on us to deliver products that don’t just meet EMC standards, but give them peace of mind that their systems will stay up and running. When a solar farm is producing power for thousands of homes, or a factory is running critical production lines, the last thing anyone needs is a switch that causes an EMC failure.
As a supplier, our job isn’t just to sell switches and disconnectors—it’s to solve our clients’ problems. We know that EMC is just one part of that, but it’s a crucial one. If you’re in the market for switches or disconnectors and want to be sure they’ll work seamlessly with your other equipment, no matter the environment, we can work with you to test and customize products to meet your exact needs. We’re not here to sell you a one-size-fits-all solution—we’re here to partner with you to understand your application, run the necessary EMC tests, and deliver a product that will keep your operations running smoothly.
If you’d like to discuss your project, have questions about our EMC testing process, or want to learn more about our switches and disconnectors, we’d be happy to connect.
Motor Control & Starters References
- International Electrotechnical Commission. (2018). IEC 61000: Electromagnetic compatibility (EMC).
- European Committee for Electrotechnical Standardization. (2020). EN 61000 series standards for EMC testing.
- Federal Communications Commission. (2021). FCC Part 15: Radio frequency devices.
- Barnes, M., & Morgan, D. (2019). Electromagnetic Compatibility for Industrial Switchgear. IEEE Transactions on Power Delivery, 34(2), 789-796.
- Smith, J. (2022). EMC Testing for Switches and Disconnectors in Renewable Energy Applications. Journal of Electromagnetic Analysis and Applications, 14(3), 112-125.
Xiamen Shengcheng Automation Co., Ltd.
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