The inductance is proportional to the square of the number of turns, that is, the inductance is proportional to the square of the number of turns and is independent of the number of turns per volt of the common mode inductance of the magnetic ring.

The number of turns per turn of magnetic ring inductance is related to the size and quality of the iron core, and the amount of inductance per turn is also related to the size and quality of the iron core, and the transformer with more turns per volt is small.

The absorption filter composed of the magnetic ring of the motor, in addition to the lossible materials with high permeability should be selected, the resistance presented by them in the line for the high-frequency components is about ten to several hundred, so its role in the high-impedance circuit is not obvious, on the contrary, in the low-impedance circuit (such as power distribution, power supply or radio frequency circuit) will be very effective.

Second, the motor magnetic ring in the high frequency band (greater than 10MHz), the inductive reactance is still very small, and the impedance is very large, so that the energy of the high frequency signal through the magnetic material, converted into heat dissipation, from blocking the passage of the high frequency signal, to inhibit the interference of the high frequency signal, usually the best suppression frequency range is related to the ferrite suppression element, usually the higher the permeability, The lower the inhibition frequency, the larger the volume of ferrite, the better the inhibition effect, when the volume is certain, the long and thin is better than the short and coarse inhibition effect, the smaller the internal force, the better the inhibition effect.

The magnetic ring of the motor has different impedance characteristics under different frequencies, the low frequency is very small impedance, the high frequency impedance rises sharply, the higher the signal frequency, the easier the magnetic field is to radiate out, the general signal line is not shielded, such as the CAN bus I use now, these signal lines become the perfect antenna, the antenna constantly receives the high frequency signals around. The superposition of these signals changes the actual signal to be transmitted, and the magnetic ring can pass useful signals well, while suppressing high-frequency interference signals.

Fourth, the motor magnetic ring suppression of common mode signal interference, the magnetic ring can signal (connected to the differential signal line) or power line (positive and negative lines) through at the same time, in order to increase the effect, can be symmetrical on the magnetic ring around a few times, increase the inductance, enhance the absorption effect of the common mode signal, but the difference signal has no effect, the component should be installed near the source of interference, For input and output circuits, they should be as close as possible to the inlet and outlet of the shielding box.