What Is an EMC Filter and Do You Need One With Your VFD?
If you’re installing a variable frequency drive (VFD), you’ve likely seen the option for an EMC filter. But what does it do—and do you really need one?
In this guide, we’ll explain what EMC filters are, how they work, and whether your application requires one. We’ll also show which VFDs come with built-in filters and when external filters are recommended.
📡 What Is an EMC Filter?
EMC stands for Electromagnetic Compatibility. VFDs generate electrical noise as they switch power rapidly to control motor speed. This high-frequency noise, known as electromagnetic interference (EMI), can affect nearby electronics, sensors, communication lines, or even trip circuit breakers.
An EMC filter reduces EMI by limiting the amount of high-frequency interference that escapes through the VFD’s input and output lines.
- ✅ Protects sensitive equipment nearby
- ✅ Helps meet CE / EN / IEC compliance
- ✅ Minimises system-level electrical noise
🛑 What Happens Without One?
Without an EMC filter, you may experience:
- 📻 Radio interference and humming sounds
- 🔌 Nuisance tripping on protection devices
- 📶 Disruption to nearby PLCs or sensors
- ⚠️ Failure to meet local EMC regulations
This is especially risky in control cabinets, automated machines, and commercial buildings.
✅ When Do You Need an EMC Filter?
You should consider using an EMC filter if:
- 📐 Your VFD is close to other sensitive electronics
- 🌐 You’re operating in an industrial or commercial EMC zone
- 🧰 You’re exporting to the EU or selling to regulated sectors
- ⚙️ Your cable runs are long, exposed, or unshielded
For critical systems, an external EMC filter with shielded cables and correct grounding is essential.
🔍 VFDs With Built-In EMC Filters
Some drives include internal EMC filters to help with compliance:
- 🟢 Delta MS300 – Class A built-in filter
- 🟢 Danfoss FC-302 – EMC options selectable
- 🟢 ABB ACS880 – Built-in Class C2/C3 filter
➡️ Always check the datasheet or product page to confirm EMC filtering levels.
⚠️ EMC Filter Classes (Quick Guide)
| Class | Standard | Application |
|---|---|---|
| Class A (C2) | EN 61800-3 2nd environment | Industrial environments |
| Class B (C1) | EN 61800-3 1st environment | Residential / commercial areas |
| Class C3 | Lower protection | Basic industrial only |
🧠 Related Reading
- IP Ratings Explained – IP20, IP66, IP65
- Do I Need a Braking Resistor with My VFD?
- Try Our VFD Sizing Calculator
🛒 Shop VFDs with Built-In EMC Filters
- 🔹 Delta MS300 – 0.75kW, IP20, Filtered
- 🔹 Danfoss FC-302 – 7.5kW, IP55, Class A
- 🔹 ABB ACS880 – 55kW, IP21, Class C2
📞 Still unsure? Contact our team for help choosing the right VFD or EMC solution.
