How are surge protection levels classified for motion controllers (MC)?

Surge protection design for motion controllers (MC) should employ a tiered approach, gradually reducing energy at each stage.

The first stage of protection is located at the system power inlet or signal line inlet, using high-current-carrying gas discharge tubes or varistors, such as the 2R series GDT or 14D series MOV, to dissipate most of the surge energy. The second stage of protection is located at the module port, using TVS diodes or lower-current-carrying varistors, such as the 5KP series TVS or 7D series MOV, to clamp residual voltage. The two stages must be decoupled via inductors, resistors, or fuses to ensure the first stage activates first. For signal ports, the capacitors of the protection devices must be compatible with the signal bandwidth. All protection device grounds should be connected to a dedicated protective ground, which is connected to the signal ground via a high-voltage capacitor or gap.

On the PCB, the surge current path should be short and straight. After design, a combined waveform test according to IEC 61000-4-5 should be performed to verify the effectiveness of the tiered protection and check for device damage. Tiered protection strikes a balance between cost and performance.