EMI RFI Noise Filters are required in two situations, to prevent EMI from an Electronic Equipment Like A Dimmer, Thyristor Drive, SMPS or Switcher affecting other Modules in a System or Neighboring Equipment.
The Second Situation is when a Sensitive Equipment Like a Medical Apparatus or Precision Measuring Instrument has to be Immune to any Noise from outside, as it can affect performance.
Sometimes it is Accuracy that can get affected, but some electrical jolts can damage or desensitize fine sensors or positioning systems.
Filters are is connected in series with an Existing Mains Chord. It can also be Fixed in a Control Panel with a Clamp. The two X caps have higher Capacitance Value. The Y cap is Lower Value and withstands around 1kV, It is better if X cap is AC 440V.
The common mode filter design in such a way that it cancels the noise. The correct winding polarity or direction is important for noise cancellation.
eEngineer – Electrical Engineering, EMI/EMC, RFI – Introduction to EMI, EMC, RFI, Military EMC Standards, Radio Frequency Interference.
EMI Shielding RF Shielding – Tech-Etch designs and manufactures both standard catalog and customized shielding products.
Dealing with Computer generated RFI/EMI – Most of the time, the RFI generated is enough to render certain bands useless and on other bands, it may drown out any weak signals and distort or interfere with signals that you want.
TDK – Electronic Components & Materials – Electronic devices generate electromagnetic interferences, which can affect the proper functioning of electronic devices and systems
Here is one type i encountered in many T&M Instruments along with TDK too. It was Schaffner – electromagnetic compatibility – International leader in electromagnetic compatibility (EMC) and power quality (PQ). EMC Filters, RFI Suppression Chokes, Feedthrough Components.