5 EFT Test (IEC 61000-4-4)

The PLC system is surrounded by cables carrying power and data. EFT events can occur from the surrounding cables and can interrupt data or power through inductive or capactive couplings. Therefore EFT immunity becomes an important requirement for PLC systems. The IEC 61000-4-4 standard defines the EFT immunity tests, set-up procedures, and test levels. Depending on the application environment, the pulse generator has varying test voltage levels depending on the application. Table 5-1 provides different test levels for EFT test for power supply ports. Test pulses are defined in Figure 5-1 by IEC 61000-4-4 standard. EFT in IEC 61000-4-4 standard are specified as repeated pulses and bursts for 15 ms with each single pulse 5 × 50 ns, as in Figure 5-1.

Figure 5-1 IEC61000-4-4 Bursts and Waveforms

Systems are classified based on their immunity to EFT, Table 5-2 provides different classifications for EFT immunity.