Switching ripple phase to earth

Often the switching ripple of modern drive applications is not visible. Not only the sampling rate of the analyzer is the limiting factor, it could be the measured voltage, too.

The diagram shows the phase to earth voltage, sampled with 1 MHz, of a switchgear with multiple drives. It shows, what happens, when filters for the common mode currents of the motor side are not equipped at a drive. We observed different faults in industrial applications, where switching ripple currents occurred at the grounding facilities of the plant.

There is only one possible solution: Filters must be equipped at the drives or one special dimensioned filter for all drives together.