Electromagnetic Interference—or EMI, as it’s commonly known—is an unavoidable challenge in modern electronics. Whether you’re working in aerospace, defense, or advanced industrial applications, EMI requirements are not just checkboxes to tick; they are mission-critical. At Advanced Conversion Technology (ACT), we understand this crucial qualification and design, build, and test with EMI in mind.
In fact, every project we undertake involves rigorous EMI considerations. Unwanted electromagnetic emissions can compromise the operation of other devices, leading to failures, safety risks, or mission degradation. For us and our customers, this won’t do. That’s why for over 40 years, ACT has worked with EMI compliance—not just as a requirement, but as a differentiator in our reliable military-grade power solutions.
At ACT, we integrate EMI management from the very beginning of the design process. As one of our senior design engineers put it: “We try to nail it every single time. We start with design, test it, and do what’s necessary to meet the requirements. EMI is built into our process, not added later.”
Let’s take a closer look at EMI, why it matters, and what it means to us at ACT.
EMI refers to unwanted electrical or magnetic fields emitted by an electronic device that interfere with the operation of other nearby electronics. These interferences can be conducted through power lines or radiated through the air.
For ACT’s high-reliability power supplies, controlling EMI is essential. The power supply must operate within stringent limits for both conducted and radiated emissions to avoid disrupting mission-critical systems—whether on an aircraft, a ship, or a ground vehicle. We use proactive design and testing methodology to mitigate EMI. Conducting testing allows our engineers to identify potential EMI sources and address any prevenient risks to ensure compliance and capability.
To design effective EMI filters, it’s important to understand the two main types of interference:
Each type requires a different approach to mitigation—this is where ACT’s experience proves especially valuable.
Filtering differential mode currents involves placing inductors in series with each power supply line and using capacitors across the lines. This configuration impedes high-frequency noise while allowing desired power frequencies to pass.
Filtering common mode currents is where common mode chokes come in. These components use two windings on a shared magnetic core. The key is that the magnetic fields from the differential (normal operating) currents cancel each other out, allowing them to pass. But if a common mode current tries to flow—i.e., current entering or exiting both lines in the same direction—the magnetic fields reinforce each other, and the inductor resists the current.
Capacitors are also used to shunt common mode noise to ground, further improving filtering.
X and Y capacitors are integral to EMI suppression, but they also come with safety considerations. X Capacitors are placed across the power lines to filter differential mode noise. Y Capacitors are connected form the power lines to ground to filter common mode noise.
In EMI, the capacitors need to be rated for specific safety standards to ensure proper operation and to avoid electric shock in the event of a capacitor failure. These safety standards ensure failure conditions and provide strict test requirements for X and Y capacitors. The safety standards are outlined in IEC 60384-14. This is the global standard for capacitors in EMI suppression and set the standards that ensure safety in electronic capacitors.
EMI suppression capacitors have two failure modes:
Our engineers’ designs account for strategic filtering and effective grounding and take the proper steps to ensure all components are appropriately rated, tested, and meet requirements.
Capacitors used in EMI filters draw leading current, which can degrade power factor. Since most power supplies aim for a unity or slightly lagging power factor, EMI filter capacitance must be carefully managed. ACT engineers work to balance this, ensuring power factor targets are met while still maintaining EMI compliance.
Our power supplies at ACT are designed to meet a wide range of EMI and EMC (Electromagnetic Compatibility) standards as well as other military standards. Here are a few we work with regularly:
Meeting these standards isn’t easy. It requires deep technical knowledge, specialized lab equipment, and a culture of engineering discipline.
Many companies outsource all EMI testing, but here at ACT, we have our own EMC pre-compliance lab. Having an in-house lab means:
It also reflects the seriousness with which we treat EMI. We don’t wait for final prototypes to “see if they pass.” We test early and we test often to solve problems before they get expensive.
We look for EMI knowledge when hiring senior engineers and ensure our junior engineers learn it early. It’s part of our DNA. Whether we’re building a rugged power supply for a military vehicle or a converter for aerospace electronics, we embed EMI considerations into the entire design lifecycle.
EMI compliance is a critical challenge in power electronics. At ACT, we design and test with EMI in mind to adhere to military and application requirements. With over 40 years of experience, an in-house lab, and a commitment to doing it right from the start, we deliver on our mission of providing power solutions that perform and protect.
If you’re an engineer or program lead seeking a partner with the experience and in-house testing to design for stringent EMI/EMC standards, let’s talk. ACT is at the ready to help you build the high-reliability systems your mission demands.
