Transient immunity generators simulate transients for the conducted immunity portion of EMC testing. A transient is a dramatic fluctuation in current or voltage a device may experience while connected to a power grid; voltage spikes and oscillations are common examples. Conducted immunity testing determines the susceptibility of the equipment under test to such disturbances. To test a device’s immunity to transients, test engineers use transient generators, also known as immunity test systems, to reproduce transients like those found in the field. Many manufacturers rent transient generators for in-house use to simulate the same waveforms a test lab will, so they can pass their product through in a timely manner.
One of the most common causes of transients in a real world setting is indirect lightning, which may strike nearby and send a surge through a grid; the electricity travels indirectly through wiring, causing electrical and electromagnetic interference. Another source of transients is electrical switching, which refers to when one device on a grid, when switched on, sends a transient to another device on the grid. Waveform variation allows for a transient generator to replicate nearly any transient a device may come across, and most transient immunity testers will include modules for specific waveforms. Transient generators designed for EMC tests on commercial, industrial, medical and IT devices comply with the following test standards in the waveforms of the transients they generate.
Commercial Conducted Immunity Test Standards