EMI Filters Bring Variable Frequency Drives Up to Speed
author: DOREXS
2025-10-29
The Lowdown on VFDs and EMI
Variable Frequency Drives (VFDs) are the unsung heroes of modern industrial automation. They're the workhorses that make it possible to control motor speed with ease and boost energy efficiency. However, the high-frequency switching of IGBT modules in VFDs generates a ton of electromagnetic interference (EMI) that can wreak havoc on nearby devices and get your equipment kicked out of international EMC standards.
Installing a high-quality VFD EMI filter is your best bet to keep this noise at bay and ensure your system runs smoothly.
Getting to the Bottom of an EMI Nightmare
A customer came to us with a problem - their industrial control system was plagued by EMI noise that was causing all sorts of issues:
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Their Programmable Logic Controller (PLC) kept on throwing errors and signals were going haywire
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Voltage distortion in the factory power grid was causing all sorts of headaches
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Communication errors between control units were common place
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EMC tests were failing left and right under EN55011 / CISPR 11 standards
We dug in and found out that the high-frequency harmonics (2–20 kHz) from the inverter's switching process were creating both common-mode and differential-mode noise that was radiating through the power line and cables.
DOREXS EMI Filter Solution Saves the Day
We provided a complete EMI suppression solution by installing filters on both the input and output sides of the VFD. Our team of experts took a comprehensive approach to tackle this problem head on.
Input Side - Stopping Noise at the Source
We installed a DOREXS DF2 Series Three-Phase EMI Filter at the inverter input. This was key to:
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Stopping conducted noise from getting out to the power grid
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cutting down common-mode current and high-frequency harmonics
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Ensuring compliance with EN 61800-3 Class A/B standards
Output Side - Smoothing Out the Ride
We also integrated a custom output sine filter between the inverter and the motor. This helped:
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Smooth out the PWM waveform and eliminate those pesky voltage spikes
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Reduce EMI radiation and keep motor insulation safe
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Extend motor lifespan and keep things running quietly
Fine-Tuning the System
We also implemented some additional tweaks to keep the system running smoothly:
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Single-point grounding to keep things stable
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Shielded cables and a proper wiring layout to keep EMI at bay
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Ferrite cores on control and signal lines to keep things under control
Test Results - EMI Filters Deliver
After installing our EMI filters, the VFD system experienced a massive improvement:
Performance Metric |
Before Installation |
After Installation |
|---|---|---|
|
EMC Compliance
|
Failed
|
Passed (EN55011 Standard)
|
|
System Stability
|
Frequent noise & misoperation
|
Fully stable
|
|
Motor Noise
|
High
|
Significantly reduced
|
|
Power Quality
|
Poor
|
Improved by 20–40 dB attenuation
|
Recommended DOREXS Products
Here are some of our top picks for EMI filters:
Performance Metric |
Before Installation |
After Installation |
|---|---|---|
|
EMC Compliance
|
Failed
|
Passed (EN55011 Standard)
|
|
System Stability
|
Frequent noise & misoperation
|
Fully stable
|
|
Motor Noise
|
High
|
Significantly reduced
|
|
Power Quality
|
Poor
|
Improved by 20–40 dB attenuation
|
The Customer Wins
By choosing DOREXS EMI Filters for Variable Frequency Drive systems, customers can reap the rewards of:
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Compliance with UL、CE / EMC standards
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Better power quality and reduced harmonic noise
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Longer equipment lifespan
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Stable industrial automation systems
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Lower maintenance and downtime
The Bottom Line
Integrating DOREXS EMI Filters into Variable Frequency Drive systems ensures full EMC compliance, minimizes electromagnetic noise, and enhances the performance and reliability of industrial equipment.
DOREXS provides advanced EMI filtering solutions for industrial automation, power electronics, renewable energy, and communication systems, helping global manufacturers achieve efficient and compliant electrical performance.
DOREXS provides advanced EMI filtering solutions for industrial automation, power electronics, renewable energy, and communication systems, helping global manufacturers achieve efficient and compliant electrical performance.
Complete Guide to EMI Filters in Industrial Automation (2025): Applications, Selection, Installation Best Practices, and ROI Impact
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