Analysis of Damped Oscillatory Wave Generators Based on IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave: A Case Study of LISUN DOW61000-18 Series

Abstract
With the rapid development of industrial electronics and power systems, electromagnetic compatibility (EMC) has become a critical criterion for ensuring the stable operation of electrical and electronic equipment. Damped oscillatory wave interference, a common electromagnetic disturbance in power grids and industrial environments, can cause malfunctions or even damage to sensitive equipment. The IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave standard specifies the testing and measurement techniques for evaluating equipment immunity to such interference. This paper takes the LISUN DOW61000-18 series Damped Oscillatory Wave Immunity Tester as a case study, systematically analyzing the technical background of the IEC 61000-4-18 standard (including slow and fast damped oscillatory wave requirements), the design principles of damped oscillatory wave generators, and the technical specifications and application scenarios of the LISUN DOW61000-18 series. Through detailed parameter comparison and principle explanation, this paper demonstrates how the LISUN product complies with the IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave requirements and provides reliable EMC testing solutions for industries such as power, industrial automation, and instrumentation.

1. Introduction
In power systems (e.g., high-voltage (HV) substations) and industrial sites, switching operations of disconnectors, circuit breakers, or other power electronic devices often generate transient electromagnetic disturbances. Among these, damped oscillatory waves are characterized by high amplitude, wide frequency range, and gradual amplitude attenuation, which can couple into the signal or power lines of nearby equipment, leading to data transmission errors, control system failures, or permanent hardware damage (IEC 61000-4-18:2022). To standardize the evaluation of equipment immunity to such interference, the International Electrotechnical Commission (IEC) developed the IEC 61000-4-18 standard, which clearly defines two types of test scenarios: Slow Damped Oscillatory Wave (Clause 4.2) and Fast Damped Oscillatory Wave (Clause 4.3).

Against this background, LISUN GROUP, a leading manufacturer of EMC testing equipment, launched the DOW61000-18 series Damped Oscillatory Wave Immunity Tester, which fully complies with the latest IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave requirements, as well as equivalent regional standards such as EN 61000-4-18 and GB/T 17626.18. This paper aims to: (1) interpret the core technical requirements of IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave; (2) introduce the design principles of damped oscillatory wave generators; (3) detail the technical specifications and performance advantages of the LISUN DOW61000-18 series; and (4) discuss its application in industrial EMC testing.

2. Interpretation of IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave Standard

The IEC 61000-4-18 standard, titled “Electromagnetic compatibility (EMC) – Part 4-18: Testing and measurement techniques – Damped oscillatory wave immunity test”, classifies damped oscillatory wave interference into two categories based on its generation mechanism and frequency characteristics: Slow Damped Oscillatory Wave (Clause 4.2) and Fast Damped Oscillatory Wave (Clause 4.3). Each category has distinct technical parameters to simulate real-world interference scenarios.

2.1 Slow Damped Oscillatory Wave (Clause 4.2)

The slow damped oscillatory wave phenomenon is primarily caused by the switching operations of disconnectors in HV/medium-voltage (MV) open-air substations, especially the switching of HV busbars (IEC 61000-4-18 Clause 4.2). When HV disconnectors are opened or closed, sharp front-wave transients are generated with a rise time of approximately tens of nanoseconds. These transients undergo multiple reflections due to impedance mismatches in HV circuits (e.g., between busbars, transformers, and cables), resulting in damped oscillatory voltages and currents on the busbars.

The core parameters of slow damped oscillatory waves specified in the standard are as follows:

• Oscillation Frequency: Determined by the length of HV busbars (ranging from tens to hundreds of meters) and signal propagation time, typically between 100 kHz and several MHz. Among these, 100 kHz is considered representative of large HV substations, while 1 MHz applies to smaller substations or shorter busbars.
• Repetition Frequency: Varies with the distance between switching contacts, ranging from a few Hz to a few kHz. For practical testing, 40 pulses per second (40/s) and 400 pulses per second (400/s) are adopted as compromise values, balancing the duration of real interference, frequency coverage, and energy stress on the Equipment Under Test (EUT).
• Voltage Attenuation: To simulate the natural decay of oscillatory waves, the standard requires that the 5th peak voltage (Vₚₖ₅) is greater than 50% of the 1st peak voltage (Vₚₖ₁), and the 10th peak voltage (Vₚₖ₁₀) is less than 50% of Vₚₖ₁.

2.2 Fast Damped Oscillatory Wave (Clause 4.3)

Compared to slow damped oscillatory waves, fast damped oscillatory waves originate from faster switching events (e.g., high-frequency power electronic switches) or shorter transmission lines, resulting in higher oscillation frequencies and shorter rise times. The IEC 61000-4-18 Clause 4.3 specifies parameters for fast damped oscillatory waves to evaluate equipment immunity to high-frequency transient interference, which is more common in modern industrial automation systems (e.g., frequency converters, servo drives) and communication equipment.

Key parameters of fast damped oscillatory waves include:

• Oscillation Frequency: Significantly higher than slow waves, typically 3 MHz, 10 MHz, and 30 MHz, covering the frequency range of high-speed digital circuits and radio frequency (RF) interference.
• Rise Time: Much shorter than slow waves (≤5 ns), reflecting the rapid transient characteristics of high-frequency switching events.
• Repetition Frequency: Up to 5,000 pulses per second (5,000/s), simulating continuous high-frequency interference in dense switching environments.
• Current Oscillation Frequency: Consistent with the voltage oscillation frequency (3 MHz, 10 MHz, 30 MHz), ensuring that both voltage and current disturbances are accurately simulated for EUTs sensitive to current coupling.

3. Design Principles of Damped Oscillatory Wave Generators

A damped oscillatory wave generator is the core component of an immunity tester, responsible for generating transient signals that comply with the IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave requirements. Its design is based on the RLC (Resistor-Inductor-Capacitor) oscillating circuit principle, with adjustments to component parameters (R, L, C) to achieve different oscillation frequencies and damping characteristics.

3.1 Basic Oscillation Principle

The generator’s core circuit consists of a DC high-voltage source, an energy storage capacitor (C), an inductor (L), a damping resistor (R), and a high-speed switch (e.g., silicon-controlled rectifier (SCR) or MOSFET). The working process is as follows:

• Energy Storage: The DC high-voltage source charges the capacitor C to a preset voltage (determining the output peak voltage).
• Oscillation Initiation: The high-speed switch is triggered, discharging C through the L-R series circuit. The interaction between C (energy storage in electric field) and L (energy storage in magnetic field) generates sinusoidal oscillation.
• Damping Attenuation: The damping resistor R consumes energy during oscillation, causing the amplitude of the sinusoidal wave to gradually decrease, forming a damped oscillatory wave.

3.2 Differences Between Slow and Fast Wave Designs

To meet the distinct parameters of IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave, the generator’s RLC parameters and switch design are optimized differently:

Slow Damped Oscillatory Wave (e.g., LISUN DOW61000-18):
• Adopts a larger L and C to achieve lower oscillation frequencies (100 kHz, 1 MHz). For example, a 100 kHz oscillation requires an L-C combination with a resonant frequency f₀ = 1/(2π√(LC)) ≈ 100 kHz.
• Uses a 200 Ω internal resistance to control the damping rate, ensuring compliance with the Vₚₖ₅ > 50% Vₚₖ₁ and Vₚₖ₁₀ < 50% Vₚₖ₁ attenuation requirements.
• Employs a medium-speed switch (rise time ≈75 ns) to match the tens-of-nanosecond rise time of slow waves.

Fast Damped Oscillatory Wave (e.g., LISUN DOW61000-18F):
• Uses smaller L and C values to achieve high oscillation frequencies (3 MHz, 10 MHz, 30 MHz). For instance, a 30 MHz oscillation requires an L-C combination with f₀ ≈ 30 MHz.
• Features a 50 Ω internal resistance (matching the characteristic impedance of high-frequency coaxial cables) to minimize signal reflection and ensure stable high-frequency transmission.
• Incorporates a high-speed switch (rise time ≈5 ns) to generate the rapid front edge of fast damped oscillatory waves.

4. Technical Specifications of LISUN DOW61000-18 Series (Compliant with IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave)

LISUN GROUP’s DOW61000-18 series includes two models: DOW61000-18 (for IEC 61000-4-18 Slow Damped Oscillatory Wave testing) and DOW61000-18F (for IEC 61000-4-18 Fast Damped Oscillatory Wave testing). Both models are calibrated to CNAS ISO 17025 standards, ensuring traceability and accuracy. Table 1 summarizes their key technical specifications.

Table 1: Technical Specifications of LISUN DOW61000-18 Series

Parameter	DOW61000-18 (Slow Damped Oscillatory Wave)	DOW61000-18F (Fast Damped Oscillatory Wave)
Compliant Standard Clause	IEC 61000-4-18/EN 61000-4-18 Clause 4.2; GB/T 17626.18 Clause 4.1	IEC 61000-4-18/EN 61000-4-18 Clause 4.3; GB/T 17626.18 Clause 4.2
Calibration Certificate	CNAS ISO 17025	CNAS ISO 17025
Output Voltage	200 V ~ 3 kV ±10%	450 V ~ 4.4 kV ±10%
Oscillation Frequency	100 kHz ±10%, 1 MHz ±10%	3 MHz ±10%, 10 MHz ±10%, 30 MHz ±10%
Pulse Polarity	Positive, Negative, or Auto (Positive/Negative)	Same as left
Rise Time	75 ns ±20%	5 ns ±30%
Voltage Attenuation	Vₚₖ₅ > 50% × Vₚₖ₁; Vₚₖ₁₀ < 50% × Vₚₖ₁	Same as left
Repeat Frequency	1~100 Hz (100 kHz oscillation); 1~1000 Hz (1 MHz oscillation)	Max. 5,000 /s ±10%
Burst Width	1~9999 s (Adjustable)	3 MHz: 50 ms ±20%; 10 MHz: 15 ms ±20%; 30 MHz: 5 ms ±20%
Pulse Interval	1~9999 s (Adjustable)	300 ms ±20%
Rise Time of Current Wave	N/A	3 MHz: <330 ns; 10 MHz: <100 ns; 30 MHz: <33 ns
Current Oscillation Frequency	N/A	3 MHz ±30%, 10 MHz ±30%, 30 MHz ±30%
Internal Resistance	200 Ω	50 Ω
EUT Power Supply	AC 600 V/32 A; DC 1000 V/32 A	AC 380 V/16 A; DC 300 V/16 A
Power Supply (Tester)	AC 85~264 V/Single Phase	Same as left
Key Test Functions	Built-in IEC standard test levels; Step voltage adjustment; Large LCD touchscreen	Same as left

4.1 Performance Advantages of LISUN DOW61000-18 Series

• Full Compliance with International Standards: Both models strictly adhere to IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave requirements, as well as EN and GB equivalents, ensuring test results are recognized globally.
• Wide Parameter Coverage: The DOW61000-18 covers 100 kHz/1 MHz oscillation frequencies for slow wave testing, while the DOW61000-18F supports 3 MHz/10 MHz/30 MHz for fast wave testing, meeting the needs of diverse EUTs.
• Flexible Operation: The built-in IEC standard test levels eliminate the need for manual parameter configuration, and the step voltage function allows users to gradually increase the test voltage to identify the EUT’s immunity threshold. The large LCD touchscreen simplifies operation and data visualization.
• High Power Supply Capacity for EUT: The DOW61000-18 provides AC 600 V/32 A and DC 1000 V/32 A for EUTs, suitable for high-power industrial equipment (e.g., HV meters, motor controllers), while the DOW61000-18F caters to medium-power devices such as communication modules.

5. Application Scenarios of LISUN DOW61000-18 Series

The LISUN DOW61000-18 series, as a professional tool for IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave testing, is widely used in industries where EMC immunity is critical. Typical application scenarios include:

5.1 Power System Equipment

• HV/MV Substation Equipment: Testing disconnectors, transformers, and protection relays for immunity to slow damped oscillatory waves generated by switching operations. The DOW61000-18’s 100 kHz/1 MHz oscillation frequencies accurately simulate real substation interference.
• Smart Meters and Energy Monitoring Devices: These devices are often installed near power lines and are susceptible to damped oscillatory waves. The tester evaluates their ability to maintain accurate measurement and data transmission under such interference.

5.2 Industrial Automation

• Frequency Converters and Servo Drives: Modern industrial automation systems use high-speed power electronic switches, which generate fast damped oscillatory waves (3 MHz~30 MHz). The DOW61000-18F tests the immunity of these devices to ensure stable motor control.
• Programmable Logic Controllers (PLCs): PLCs are the core of industrial control systems. Slow wave interference (from HV busbars) or fast wave interference (from nearby switches) can cause logic errors. The DOW61000-18 series verifies their anti-interference capability.

5.3 Instrumentation and Medical Equipment

• Precision Instruments: Laboratory equipment (e.g., oscilloscopes, signal generators) and process control instruments (e.g., pressure transmitters) require high stability. The tester ensures they are not affected by damped oscillatory waves in industrial environments.
• Medical Devices: Devices such as patient monitors and diagnostic equipment must operate reliably in hospitals, where power grid switching may generate damped oscillatory waves. The IEC 61000-4-18 testing (using LISUN’s tester) is a mandatory step for medical device certification.

6. Conclusion
The IEC 61000-4-18 Slow and Fast Damped Oscillatory Wave standard plays a vital role in ensuring EMC immunity of electrical and electronic equipment, addressing the risks posed by damped oscillatory wave interference in power systems and industrial environments. The LISUN DOW61000-18 series Damped Oscillatory Wave Immunity Tester, with its strict compliance with the standard, wide parameter coverage, and user-friendly design, provides a reliable testing solution for industries worldwide.

The DOW61000-18 model effectively simulates slow damped oscillatory waves (100 kHz/1 MHz) for HV substation equipment, while the DOW61000-18F targets fast damped oscillatory waves (3 MHz/10 MHz/30 MHz) for high-frequency industrial and communication devices. Both models not only meet the technical requirements of IEC 61000-4-18 but also enhance testing efficiency through intelligent functions such as built-in standard levels and step voltage adjustment.

As industrial electrification and digitalization continue to advance, the demand for EMC testing will grow further. The LISUN DOW61000-18 series, by aligning with global standards and practical application needs, will remain a key tool for ensuring equipment reliability and promoting the development of EMC-compliant products.

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