Where is the optimal installation location for the inverter magnetic ring?

Determining the optimal installation location of the magnetic ring in a frequency converter system is crucial for suppressing common-mode and differential-mode noise. The magnetic ring absorbs noise energy through its high-frequency loss characteristics. To suppress conducted emissions from the input power lines, the magnetic ring should be installed close to the power input of the frequency converter, ideally after the EMI filter and before the internal components of the frequency converter. To suppress radiated and conducted common-mode noise from the motor cables, the magnetic ring should be installed as close as possible to the output terminals of the frequency converter, fitted onto each phase cable and ground wire, or an integrated output magnetic ring assembly can be used. To suppress internal noise coupling, magnetic rings can be fitted onto drive signal lines, sensitive analog lines, or DC buses.

The installation principle is to install the magnetic ring near the noise source or on the path of the noise current. The magnetic ring should tightly wrap around the cable; if necessary, several turns can be added to increase inductance, but care must be taken to ensure that the inter-turn capacitance affects high-frequency performance. The choice of magnetic ring material depends on the noise frequency band to be suppressed; manganese-zinc ferrite is suitable for the low-frequency range (<10MHz), and nickel-zinc ferrite is suitable for the high-frequency range (>10MHz). By comparing noise levels before and after installation using near-field or current probes, the optimal placement of the magnetic ring can be verified. Eintech offers magnetic rings in various sizes and materials and can recommend installation solutions based on the application scenario.