How to select a common-mode choke for inverter communication

The selection of common-mode chokes for various communication ports of the frequency converter must be determined based on the communication protocol, data rate, and interference frequency band. Key parameters include: differential-mode inductance, common-mode impedance frequency curve, rated current, DC resistance, and impedance. For low-speed interfaces such as RS485 and CAN, with data rates below 1Mbps, models with differential-mode inductance values ranging from tens to hundreds of μH can be selected, such as the CMZ3225A series. Their common-mode impedance peak value is typically in the range of several MHz to tens of MHz, effectively suppressing switching noise. For high-speed interfaces such as Ethernet (100/1000Mbps), models with good high-frequency performance should be selected, with high common-mode impedance values in the tens to hundreds of MHz range, such as the CMZ2012A-900T.

Simultaneously, their differential-mode inductance should be very small to avoid affecting signal integrity. The rated current must be greater than the maximum current flowing through the signal line. While communication current is usually small, fault conditions must be considered. The DC resistance (DCR) should be as small as possible to reduce signal attenuation. The package size must comply with PCB space constraints. When selecting a component, refer to the impedance-frequency curve provided by the supplier and choose the model with the highest impedance at the frequency where interference exceeds the standard or at a multiple of the communication frequency. Yinte Electronics' CMZ series common-mode chokes are available in various specifications to meet the needs of different communication ports in frequency converters.