Common Mode Choke
What is a Common Mode Choke?
A common mode choke is an electrical filter that is utilized to block or limit unwanted high frequency alternating current (AC) noise within an electrical system while allowing the desired lower frequency direct current (DC) to pass through. Common mode (CM) noise current is typically radiated from sources such as unwanted radio signals, unshielded electronics, inverters and motors. Left unfiltered, this noise presents interference problems in electronics and electrical circuits.
Selection Considerations for Common Mode Chokes
When selecting a common mode choke for a given application, it is important to consider the specific requirements and restrictions of the system for which it is being installed. Gowanda’s common mode chokes are manufactured in a wide range of sizes and designs to suit a variety of use cases. As a general rule, larger chokes are capable of filtering lower frequencies than smaller chokes, making them suitable for equipment that requires more accurate noise filtering, such as AC/DC outlets.
Key factors to consider when selecting a choke are:
- Current Rating: to ensure the part does not overheat within the application
- Impedance vs. Frequency: to ensure it is optimized to attenuate the desired frequencies.
- Isolation Voltage: to ensure it meets board level requirements between the line and neutral phases.
- Safety Isolation: to ensure it meets the safety requirements of the end application.
- It is typical for the inductance value of a common mode choke to be specified as a minimum requirement, thus insuring the crossover frequency is not shifted too high.
- The frequency range of the interfering signal should be provided in order to allow proper calculation of the attenuation of unwanted signal noise in the design.
- Proper wire sizing is accomplished by specifying the voltage and current levels across, and passing through, the common mode choke.
Common mode choke filter, line inductor, and differential choke designs vary widely in terms of power rating, inductance, voltage level (low to high), operating frequency, size, impedance, bandwidth (frequency response), packaging, winding capacitance, and other parameters.
Applications of Common Mode Chokes
Common mode chokes are commonly used to reduce or eliminate electromagnetic interference (EMI) in industrial applications that require a steady and reliable current without interruption. Typical electrical and electronic devices that may use common mode chokes include:
Audio/Visual (AV) signaling equipment
Conveyors and elevators
Industrial tool drives
Oil and gas control systems
Switch mode power supplies
Train signaling systems
Variable frequency drives (VFDs)
Surface Mount Transformer
Gowanda welcomes the opportunity to assist its customers with application-specific designs for a particular application where the requirements can not be met by off-the-shelf components.
Our capabilities in design, development, production and testing are extensive. If you are interested in custom products please contact us for assistance.