How to adapt industrial servo output reactors to EMC?

Servo output reactors are primarily used to limit di/dt, reduce motor terminal voltage spikes, and suppress common-mode current in cables. Their EMC compatibility requires comprehensive consideration of inductance value, saturation characteristics, and high-frequency impedance. Etymotics recommends the following: First, calculate the required inductance based on the motor cable length and IGBT switching speed, typically selecting 20μH-50μH per phase (e.g., PWR series power inductors). The reactor must have a low parasitic capacitance design to prevent impedance drop at high frequencies. To enhance EMC performance, reactors with built-in common-mode chokes can be used, or PBZ ferrite beads (e.g., PBZ2012E-220Z0T) can be connected in series at the reactor output.

Compatibility verification: Under full load, the reactor temperature rise should be <70K, and the peak motor terminal voltage should not exceed 80% of the IGBT withstand voltage. Spectrum testing shows that adding a well-matched output reactor can reduce radiated interference from the motor cable in the 10-30MHz frequency band by 8-12dB. At the same time, attention should be paid to the impact of the voltage drop generated by the reactor on the motor torque, which needs to be compensated in the control parameters.