Introduction to Conducted Emissions in Electromagnetic Compatibility (EMC)
Conducted emissions refer to unwanted high-frequency electrical noise propagated via power lines or signal cables, which can interfere with the operation of electronic devices. These emissions originate from switching power supplies, motor drives, digital circuits, and other high-frequency components. Compliance with international EMC standards is mandatory for ensuring that electronic equipment does not disrupt other devices or violate regulatory requirements.
Conducted emissions testing evaluates the amplitude of these disturbances across specified frequency ranges, typically from 9 kHz to 30 MHz. The testing process involves measuring noise voltages on power supply ports using specialized equipment such as the LISUN EMI-9KB Conducted Emissions Test System, which ensures adherence to standards like CISPR, EN, FCC, and IEC.
Fundamentals of Conducted Emissions Measurement
Conducted emissions are categorized into two types:
- Differential Mode (DM) Noise – Current flows in opposite directions along power or signal lines.
- Common Mode (CM) Noise – Current flows in the same direction, often due to parasitic capacitances or ground loops.
The LISUN EMI-9KB employs a Line Impedance Stabilization Network (LISN) to provide a standardized impedance (50 Ω/50 μH) for repeatable measurements. The system captures noise signals, processes them via an EMI receiver, and compares results against regulatory limits.
Key Standards Governing Conducted Emissions Testing
Different industries must comply with specific EMC standards:
| Industry | Applicable Standard | Frequency Range |
|---|---|---|
| Household Appliances | CISPR 14-1, EN 55014-1 | 150 kHz – 30 MHz |
| Medical Devices | IEC 60601-1-2, EN 60601-1-2 | 150 kHz – 30 MHz |
| Industrial Equipment | CISPR 11, EN 55011 | 9 kHz – 30 MHz |
| Automotive Electronics | CISPR 25, ISO 7637-2 | 150 kHz – 108 MHz |
| IT Equipment | CISPR 32, EN 55032 | 9 kHz – 30 MHz |
The LISUN EMI-9KB is designed to meet these standards, ensuring accurate and compliant testing across multiple sectors.
The Role of the LISUN EMI-9KB in Conducted Emissions Testing
The LISUN EMI-9KB Conducted Emissions Test System is a high-precision instrument used for measuring disturbances on AC/DC power lines. Its key features include:
- Frequency Range: 9 kHz – 30 MHz (extendable with optional modules)
- Compliance: CISPR 16-1-1, CISPR 16-2-1, EN 55016
- Measurement Accuracy: ±1.5 dB
- Integrated LISN: 50 Ω/50 μH impedance for stable measurements
- Automated Reporting: Direct data export for certification
Testing Workflow with the EMI-9KB
- Device Under Test (DUT) Connection: The DUT is powered through the LISN, which isolates external noise.
- Signal Acquisition: The EMI receiver captures conducted noise via the LISN’s RF output.
- Data Analysis: The system compares measured emissions against predefined limits.
- Compliance Verification: Reports are generated for regulatory submission.
Industry-Specific Applications of Conducted Emissions Testing
Lighting Fixtures and LED Drivers
Switching power supplies in LED drivers generate high-frequency noise. The EMI-9KB ensures compliance with EN 55015 for lighting equipment.
Medical Devices and Patient Safety
Electrosurgical units and MRI machines must avoid interference with sensitive monitoring equipment. The EMI-9KB verifies compliance with IEC 60601-1-2.
Automotive Electronics and EV Chargers
Electric vehicle chargers introduce significant conducted noise. The EMI-9KB aligns with CISPR 25 for automotive EMC requirements.
Industrial Motor Drives and Robotics
Variable frequency drives (VFDs) produce harmonic distortions. The EMI-9KB tests conducted emissions per EN 61800-3.
Competitive Advantages of the LISUN EMI-9KB
- High Accuracy and Repeatability: Precision components ensure measurement consistency.
- Broad Industry Compliance: Supports multiple standards without reconfiguration.
- User-Friendly Software: Automated limit line comparisons and report generation.
- Robust Shielding: Minimizes external interference for reliable results.
Mitigation Techniques for Excessive Conducted Emissions
If a device fails testing, engineers employ:
- Ferrite Chokes: Suppress high-frequency noise on cables.
- X/Y Capacitors: Filter differential and common mode noise.
- Improved PCB Layout: Reduces ground loops and parasitic coupling.
The EMI-9KB assists in validating these fixes through iterative testing.
Future Trends in Conducted Emissions Testing
With the rise of 5G and IoT, higher-frequency noise (up to 300 MHz) is becoming a concern. The EMI-9KB is future-proofed with modular upgrades for extended frequency analysis.
FAQ Section
Q1: What is the difference between conducted and radiated emissions testing?
Conducted emissions measure noise on power/signal cables, while radiated emissions assess electromagnetic fields in the air.
Q2: Can the EMI-9KB test both AC and DC power lines?
Yes, the system supports both AC (up to 400 V) and DC (up to 1000 V) power sources.
Q3: How often should conducted emissions testing be performed?
Testing is required during product development, certification, and after major design changes.
Q4: Does the EMI-9KB support automated compliance reporting?
Yes, it integrates with LISUN’s EMI test software for instant report generation.
Q5: What industries benefit most from the EMI-9KB?
Medical, automotive, industrial, and IT sectors rely on it for regulatory compliance.
