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Installing the power filter precautions
Sep 05, 2018

Installing the power filter precautions

The power line filter is preferably installed at the power line input of the device because installation and wiring have a large impact on the performance of the filter. Filters are an obstacle to high frequency signals and their function must never fail due to discretely coupled power supply input lines, with power supply output lines, or any other conductor of a protected device. Therefore, when installing the power filter, pay attention to the following four points:

First, do not install the filter inside the shield of the device. Because of this, the EMI signal on the internal circuits and components of the device is directly coupled to the outside of the device due to the EMI signal generated by the radiation on the end leads of the filter, so that the device shielding loses the suppression of EMI radiation generated by the internal circuits and components.

Second, when tying equipment, it is strictly forbidden to bundle the input and output cables of the filter together. This exacerbates the electromagnetic coupling between the input and output of the filter, severely damaging the filter's ability to suppress EMI signals.

Third, there must be a good electrical connection between the outer casing of the mains filter and the ground of the equipment. Do not install the filter on an insulating material board or painted surface, and install it on a metal case. Also avoid using long ground wires, which will greatly increase the grounding inductance and resistance, which will seriously reduce the common mode rejection of the filter. A better method is to use a metal screw and a spring (star) washer to secure the metal shield of the filter to the chassis at the system power inlet or to the location with a copper braided ground strap.

Fourth, use the original shielding of the device as much as possible to effectively isolate the input and output ends of the filter, and control the electromagnetic coupling between the input and output of the filter to a minimum.

The housing of the general filter is connected to the frame or casing of the protected equipment. The wire side conductors should be kept short and well isolated from the load side conductors. The ideal isolation system is a wall-mounted filter with an incoming socket.

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