High Quality Filter in Dc Power Supply

Certifications and Market BenefitsWith our support, the client successfully achieved UL certification and EMC compliance—marking a vital step toward expanded global market access. These certifications validate the product’s safety, reliability, and electromagnetic compatibility, reinforcing the manufacturer’s industry reputation and customer confidence.Our Commitment to Customer SuccessWe pride ourselves on delivering tailored testing solutions aligned with international standards, empowering our clients to meet regulatory requirements efficiently. Our team’s deep technical expertise and proactive approach ensure that product development cycles are shortened, costs are controlled, and compliance is achieved with confidence.As industry leaders in EMC testing support, we remain dedicated to helping manufacturers like yours excel in global markets by providing expert guidance, advanced testing services, and strategic solutions.ConclusionAchieving EMC compliance is a complex but critical process. With our comprehensive testing services and technical support, your products can successfully meet international standards—accelerating your journey toward global certification and market success.

So, how can the performance of power filters be tested?


Leakage Current

Leakage current refers to the current flowing between the phase line, neutral line, and the filter casing (ground line) under a voltage of 250VAC. It primarily depends on the value of the ground capacitor (common mode capacitor). A larger common mode capacitor CY can improve insertion loss but may result in higher leakage current.


Withstand Voltage

To ensure the performance of the power filter, as well as the safety of equipment and personnel, withstand voltage testing must be conducted. Withstand voltage testing is performed under extreme operating conditions. If the withstand voltage performance of the CX capacitor is poor, it may break down when peak surge voltage occurs. While its breakdown may not endanger personal safety, it can cause the filter to lose functionality or performance.


Performance Evaluation

When using EMI power filters, the most important considerations are the rated voltage and current values, withstand voltage performance, and leakage current. The primary performance evaluation of a filter is its insertion loss performance.

The ability of an EMI power filter to suppress interference noise is measured using Insertion Loss (I.L.). Insertion loss is defined as the ratio of the power P1 transmitted from the noise source to the load without the filter connected to the power P2 transmitted from the noise source to the load with the filter connected, expressed in decibels (dB).


Standard Insertion Loss Testing
Load Insertion Loss Testing
Time Domain Testing for EMI Filters


Design of an Automatic Insertion Loss Testing System for EMI Filters

As EMC testing becomes more complex and the workload increases, the requirements for testing equipment in terms of functionality, performance, testing speed, and accuracy are also rising. Traditional manual testing is increasingly unable to meet these requirements. National standards (GB) and national military standards (GJB) both require EMC testing to be automated, with strict requirements for data post-processing. Therefore, the development of EMC automatic testing has become essential. The automatic testing system established in this article utilizes virtual instrument technology and is based on a signal source and spectrum analyzer to test the insertion loss of EMI power filters.

At VIIP Filter, we recently had the opportunity to assist a customer with their vending machine project, helping them to achieve UL certification. This case study showcases our efforts in providing EMI power filters and technical expertise to overcome EMC issues and successfully pass laboratory testing.

Project Description:

The vending machine initially faced challenges in passing UL certification due to electromagnetic compatibility (EMC) issues. Our engineering team intervened by implementing various solutions to address the problem and ensure compliance with industry standards.

First Attempt: Installing VIIP Filter EMI Power Filters

In the first attempt to mitigate the EMC issues, we installed four of our 20A single-phase filters in the vending machine. Despite this intervention, the certification was still not achieved, prompting us to explore additional solutions.

Second Attempt: Adding Ferrite Core Rings

To further improve EMC performance, our engineer onsite added two ferrite core rings (magnetic toroids) to the vending machine. While this adjustment helped reduce margin issues, there was still a small residual offset that needed to be addressed.

Upgraded Filters and Ferrite Rings

Following the feedback from the laboratory testing, our engineering team decided to upgrade the previous single-phase filters and reintroduce the ferrite rings. With these improvements in place, the vending machine underwent EMC tests once again, and this time, it successfully passed the certification requirements.

The Role of VIIP Filter EMI Power Filters:

VIIP Filter's EMI power filters played a crucial role in improving the vending machine's EMC performance. By providing reliable filtering solutions, we helped our customer enhance the machine's electromagnetic compatibility, ensuring compliance with UL certification standards.

Technical Expertise and Onsite Support:

In addition to supplying EMI power filters, our engineering team offered valuable technical expertise and onsite support throughout the certification process. By closely collaborating with the customer and addressing specific EMC challenges, we were able to identify the root cause of the issue and implement effective solutions.

The successful outcome of this project highlights VIIP Filter's commitment to quality, innovation, and customer satisfaction. By leveraging our EMI power filters and technical knowledge, we were able to assist our customer in overcoming EMC issues and achieving UL certification for their vending machine. This case study exemplifies our dedication to providing reliable filtering solutions and personalized support to meet our clients' unique requirements.

I. Basic Principles of Three-Phase AC Filters

A three-phase AC filter is a device used to filter specific frequency harmonics in three-phase AC power. Its basic principle involves using components such as inductors and capacitors to form a resonant circuit that absorbs or suppresses specific frequency harmonics, thereby improving power quality. Three-phase AC filters are typically composed of multiple single-phase filters to adapt to the characteristics of three-phase AC power.

II. Classification of Three-Phase AC Filters

Three-phase AC filters can be classified into two main categories: passive filters and active filters, based on their filtering principles and application scenarios.


Passive Filters: These filters are primarily composed of passive components such as inductors, capacitors, and resistors. They have a simple structure, low cost, and are suitable for scenarios with low harmonic content and less demanding filter performance.
Active Filters: These filters work by detecting harmonic currents in the power grid and generating compensating currents that are opposite in phase to eliminate the harmonics. Active filters have advantages such as fast response and good filtering effects, but their cost is relatively high.

III. Applications of Three-Phase AC Filters

Three-phase AC filters have a wide range of applications in power systems, including the following aspects:


Harmonic Mitigation: In power systems, various nonlinear loads (such as rectifiers and inverters) can generate substantial harmonic currents that threaten the stable operation of the grid and the safety of equipment. Installing three-phase AC filters can effectively filter out these harmonic currents, improving power quality.
Power Factor Correction: Some power electronic devices generate reactive power during operation, resulting in a lowered power factor in the grid. Three-phase AC filters can compensate for reactive power, improving the power factor and reducing line losses.
Voltage Fluctuation Suppression: In power grids, voltage may fluctuate due to load changes or faults. Three-phase AC filters can adjust their parameters to suppress voltage fluctuations and enhance grid stability.

IV. Design and Optimization of Three-Phase AC Filters

To meet the needs of different power systems, the design and optimization of three-phase AC filters are particularly important. During the design process, it is crucial to consider factors such as the harmonic characteristics of the power grid, types of loads, and filter costs, to select suitable filter types, parameters, and topologies. Additionally, simulation analysis and experimental validation of the filters are necessary to ensure good filtering performance and stability in practical applications.

V. Conclusion

As key components in power systems, three-phase AC filters play an essential role in ensuring power quality and suppressing harmonic interference. With the continuous development of power electronic technology and the expanding application fields, the design and optimization of three-phase AC filters will gain increasing attention. Looking ahead, we have reason to believe that three-phase AC filters will play an even more important role in power systems, contributing significantly to the prosperity and development of the electricity sector.