1. What is EFT/B test?
EFT/B is short for electrical fast transient/burst, it is a basic EMC test. The repetitive fast transient test is a test with bursts consisting of a number of fast transients, coupled into power supply, control, signal and earth ports of electrical and electronic equipment. And then evaluate the impact on the original performance of the device under test when it suffers from transient disturbances. Mechanical switches in circuits often cause interference to other electrical and electronic equipment when switching inductive loads.
The characteristics of this interference are that pulses appear in groups, the repetition frequency is high, the rise time of the pulse waveform is short, but the energy of a single pulse is relatively small, usually does not cause equipment failure, but it can cause equipment malfunction to occur frequently. The reason why transients interference can cause equipment malfunction is that the transients will charge the junction capacitance of the semiconductor device in the line. When the energy on the junction capacitance accumulates to a certain extent, it will trigger the equipment to malfunction.
2. How to perform the EFT/B test?
The standard IEC61000-4-4 gives immunity requirements and test procedures related to electrical fast transients / bursts, so that to evaluate the immunity of electrical and electronic equipment when subjected to electrical fast transient / burst on supply, signal, control and earth ports. The EFT/B generator is to simulate the disturbance caused by switching inductive loads by mechanical switches in the power grid, and the transient disturbances are applied between the power line and the ground by the coupling and decoupling network. So the essence of this test is a common mode test, the test levels are given by table 1 of standard IEC61000-4-4.
A capacitive coupling clamp is a device that couples fast transient bursts onto the line under test without making a direct electrical connection to any port, cable shield, or other part of the equipment under test. The cable under test (signal line) is placed between the upper and lower coupling plates of the coupling clamp. The coupling clamp itself should be closed as tightly as possible to provide the maximum coupling capacitance between the cable and the coupling clamp. The interference exerted through the coupling clamp still has a common-mode nature. however, direct injection is preferred.
3. The significance of EFT/B test
The electrical fast transient / burst immunity test is one of the more difficult to pass among all immunity tests, and it is also a test with poor repeatability and comparability. The test is an anti-common-mode interference test, which determines the need to take effective measures against common-mode interference when dealing with interference.
The transient disturbance will affect the device under test in two ways during the transmission process: 1) part of it enters the device through the transmission line (conducted emission); 2). and the other part overflows from the line and enters the device in the form of a radiated signal (radiated emission). Therefore, the interference experienced by the equipment under test is actually the combined effect of conduction emission and radiation emission.However, the conduction emission dominates the transient interference, and its amount is controllable and significant.
PEGO has launched multiple models of EFT/B generators to satisfy different test demands, and built-in coupling and decoupling networks. Model EFT-6K16 can output 6KV voltage (open circuit) and built in 380V/16A CDN. Model EFT-5K16 can output 5KV voltage (open circuit) and built-in 380V/16A CDN. Model EFT-6K30 can output 6KV voltage and built in 380V/30A CDN. And we can support customized equipment as per the user’s test requirements.
