To ensure current loop stability, a minimum load inductance is essential for the proper operation of PWM servo drives. If the load inductance is less than the minimum rating for the servo drive, Filter Cards can be used to add inductance to the motor/drive system.
For example, if the servo drive datasheet calls for a minimum inductance of 250uH, and your motor only has 25uH, then the addition of the BFC15030 will ensure proper operation. The total inductance for the motor and filter card will be 25uH + 300uH = 325uH.
Inductive filter cards are also used to reduce the PWM switching noise that occurs with high power supply voltages (>250VDC) and long cable runs (>10m).