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Considerations for EMI Filter
Dec 20, 2018

EMI Power filters must pay attention to the installation of the filter when applied, because if the filter is not installed properly, it will get a worse effect.

1, in order to make the EMI filter safe and reliable operation (heat dissipation and filtering effect), in addition to the EMI filter must be installed in the device rack or chassis above, but also to ensure that the EMI filter connection location and equipment chassis grounding point to achieve consistency, and minimize the EMI filter grounding line. If the pick-up location is not in one place, then the leakage current and noise current of the EMI filter will be introduced into other parts of the device as the path through the two-way location is flowing through. In addition, the grounding line of the EMI filter will introduce inductance, which can lead to the deterioration of the high frequency attenuation characteristics of the EMI filter. Therefore, the EMI filter of the metal housing should be connected directly to the device chassis. If the shell is sprayed with paint, it must be scraped off the lacquer, if the metal shell of the EMI filter can not be directly grounded or the use of plastic seal shell EMI Filter, it and the device chassis grounding line should be short.

2, EMI filter to be installed in the device power cord input, the connection should be as short as possible, the device internal power supply to be installed in the output of the EMI filter.

If the input line of the EMI filter in the device is long, the input line at the high frequency end will be coupled to the other parts of the conduction interference, and if the internal power supply of the device is installed on the input side of the EMI filter, the same result will be caused by too long the connection.

3, to ensure that the EMI filter input line and output line separation. If the EMI filter inputs, output lines are bundled together or installed too close to each other, the high frequency attenuation of the EMI filter may be reduced due to the coupling between them. If the input and output lines must be close, then both twisted-pair or shielded lines must be used.