How to protect against EFT fast pulses in frequency converters

To protect inverters from EFT (Electronic Fast Transient) pulse interference, the design must address its rapid rise and repetitive pulse characteristics. EFT primarily enters through power and signal lines. Power line protection is crucial; a combination of devices capable of absorbing fast pulse energy should be installed at the AC or DC power input, such as varistors (e.g., the 14D series), TVS diodes (e.g., the SMCJ series), and common-mode inductors. Varistors absorb most of the energy, while TVS diodes clamp the voltage. For internal DC power branches, a TVS diode and ferrite bead filter can be added to each sub-power input. For signal line protection, using isolated transceiver chips at communication ports is the most effective method. If isolation is not available, high-speed TVS diodes or dedicated EFT protection devices must be used on the signal lines, along with common-mode chokes. In PCB layout, protection circuitry must be placed close to the interface, and the ground wire of the protection device should be short and thick, directly connected to the chassis ground or a separate protective ground plane to provide a fast discharge path for pulse current. Pre-testing with an EFT generator should be performed to observe whether the equipment experiences resets or malfunctions, and targeted protection should be strengthened accordingly. Eintech offers a complete portfolio of devices and reference designs for EFT protection, helping inverters improve their immunity.