Common Mode Chokes: Theory and Applications for Electromagnetic Compatibility

Common mode chokes are essential components in electronic circuits, designed to suppress electromagnetic interference (EMI) while allowing desired signals to pass through. This comprehensive guide covers the theory behind common mode chokes, their design features, and their applications across various industries.

What is a Common Mode Choke?

A common mode choke is an inductive device consisting of two or more windings wrapped around a magnetic core. Its primary function is to block common mode noise—interference that appears equally on both conductors—while allowing differential signals to pass. This makes common mode chokes vital for improving electromagnetic compatibility (EMC) in electronic systems.

How Common Mode Chokes Work

Common mode chokes operate based on the principle of magnetic coupling. When a differential signal is applied, the magnetic fields generated by the windings oppose each other, resulting in minimal impedance. However, when common mode noise is present, the magnetic fields reinforce each other, creating high impedance that effectively blocks the unwanted noise.

Key Characteristics:

Applications for Common Mode Chokes

Common mode chokes are widely used in various applications, including:

Power Supplies
Data Communication Lines
Audio Equipment
Industrial Equipment
Electrical Ballasts
HVAC Systems
Industrial Tool Drives
LED Lights
Medical Equipment
Oil & Gas Control Systems
Robotic Equipment
Train Signaling Systems
Variable Frequency Drives (VFDs)

Design Considerations

When designing a common mode choke, several factors must be taken into account:

Core Material: The choice of core material affects the choke’s performance at different frequencies. Ferrite cores are commonly used for high-frequency applications.
Winding Configuration: The arrangement of windings influences inductance and coupling efficiency.
Environmental Factors: Considerations such as temperature range and humidity can impact choke performance.

Gowanda's Common Mode Choke Solutions

At Gowanda Electronics, we specialize in designing custom common mode chokes tailored to meet specific application requirements. Our engineering team collaborates closely with clients to optimize designs for performance, size, and cost-effectiveness. We offer a range of standard and custom solutions suitable for various applications.

Conclusion

Common mode chokes are vital components for enhancing electromagnetic compatibility in electronic systems. By effectively suppressing unwanted noise while allowing desired signals to pass, they contribute significantly to the reliability and performance of various applications. Contact Gowanda Electronics today to learn more about our custom common mode choke solutions and how we can help you achieve your design goals.

Standard Product Series Information

Radial Lead Transformer

Series	L µH	DCR Ohms	Current Rating mA DC
CMF4H	100 – 10000	0.0025 – 0.390	1.20 – 15
CMF4HC	100 – 10000	0.004 – 0.390	1.20 – 12
CMF4VM	100 – 10000	0.0025 – 0.390	1.20 – 15
CMF5H	750 – 15000	0.009 – 0.250	2.0 – 12.50
CMF5VM	750 – 15000	0.009 – 0.250	2.20 – 11.80

Surface Mount Transformer

Series	L µH	DCR Ohms	Current Rating mA DC
CMF1SM	100 – 1000	0.026 – 0.658	0.50 – 2.80
CMF2SM	100 – 1000	0.035 – 0.210	1.20 – 3.00
CMF3SM	25 – 2500	0.010 – 0.150	2.20 – 8.50
CMF61SM	25 – 2200	0.010 – 0.750	0.18 – 3.0
CMF63SM	33 – 4700	0.007 – 1.050	0.25 – 5.50
CMF64SM	100 – 10000	0.006 – 0.90	0.33 – 7.0
CMF65SM	100 – 15000	0.005 – 1.10	0.35 – 8.50
CMN3VSM	180 – 10000	0.0019 – 0.0347	3.80 – 16.40

Question?

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Custom Products

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.

Common Mode Choke