What is the function of EMI filters?

What is the function of EMI filter? There is no standard answer to this question. Now, Green Wave Jie can talk about his understanding of the role of EMI filters. The function of EMI filter, in simple terms, is to eliminate EMI and achieve EMC. If expanded, it would be to eliminate electromagnetic interference issues and achieve electromagnetic compatibility. This is our understanding of the role of EMI filters.

1、 What is EMI
Before discussing the function of EMI filters, it is necessary to first understand what "EMI" means. EMI stands for Electromagnetic Interference in English, which translates to electromagnetic interference in Chinese.

Electromagnetic interference refers to the phenomenon of electromagnetic interference generated by the interaction between electromagnetic waves and electronic components. Electromagnetic interference can be divided into two types: conducted interference and radiated interference, and some also divide it into three types: conducted interference, coupled interference, and radiated interference.

2、 What is EMI filter
After we understand the concept of EMI, the next question is, what exactly is an "EMI filter"? A more common explanation for EMI filters is: EMI filters, also known as "electromagnetic interference filters," are electronic and electrical equipment mainly used to suppress electromagnetic interference, especially electromagnetic interference (noise) in circuits.

Features such as MLAD-V-SR inverter specific input filter, MLAD-SR servo specific input filter, MLAD-GFC series LCL harmonic filter, MLAD-APF active harmonic filter, etc., can all be referred to as "EMI filters"; Of course, some people also refer to MLAD-V-SC inverter specific output filters, MLAD-S-SC servo specific output filters, MLAD-DW series Du/dt filters, MLAD-SW sine wave filters, etc. as "EMI filters".

3、 EMI filter function
With the more concrete "EMI filter" products mentioned above, it will be easier to understand the function of EMI filters. The main functions of EMI filters can be summarized as follows:

1. Suppress high-order harmonics
MLAD-GFC series LCL harmonic filters, MLAD-APF active harmonic filters, etc., all have the same function of suppressing high-order harmonics as MLAD-VR-SR inverter specific input reactors, MLAD-SR-SR servo specific input reactors, etc.

2. Suppress high-frequency harmonics
Special input filters such as MLAD-V-SR frequency converter and MLAD-S-SR servo have good suppression effects on high-frequency harmonics, especially in the frequency range of 10KHz~30MHz, where the filtering effect is even better.

3. Assist in EMC testing
Nowadays, people are paying more and more attention to EMC. In most certifications, there are EMC testing requirements. In order to meet the EMC testing requirements and pass EMC testing smoothly, EMI filters are generally needed for assistance. Otherwise, it is generally difficult for the product/equipment/device itself to pass EMC testing.

4. Assist in achieving harmonic standards
There are many industry standards, national standards, and international standards that limit the size of THD. It is common to require THD to be ≤ 5% or 10%. Obviously, it is difficult to control this level solely by the product/equipment itself. At this time, EMI filters such as MLAD-APF source harmonic filters, MLAD-GFC series LCL harmonic filters, and MLAD-SW sine wave filters can be used to assist the product/equipment in achieving relevant industry, international, and international standards.

4、 The difference between EMI filter and EMC filter
What are the differences between EMI filters and EMC filters? This is also one of the frequently asked questions. In fact, strictly speaking, there is not much difference between these two, it's just different names for the same product.

EMI stands for electromagnetic interference, while EMC stands for electromagnetic compatibility. Eliminating electromagnetic interference is to achieve electromagnetic compatibility.

If one has to distinguish between EMI filters and EMC filters, EMI filters generally refer to filters used on the power supply side of harmonic sources, such as input filters for MLAD-V-SR frequency converters; EMC filters generally refer to filters used on the output side of harmonic sources, such as MLAD-V-SC frequency converter specific output filters.