Conducted Emissions Feedback from VSD operated products : What can we learn from testing actual VSD driven products?

The ubiquitous increase in the use of mains power switching devices has been paralleled by the increase in ‘nuisance tripping’ of GFCIs and other protection devices. The GFCI uses the change in line current levels to detect fault current diverted to earth/ground, an electric shock hazard to humans. Examples of >1MHz conducted high frequency threat signals generated are shown in this paper; their relationship to electric shock touch current is described. False tripping of GFCIs is shown. ‘Nuisance tripping’ can be identified to contain such high frequency signals and these must be properly taken into account when designing proper GFCI operation in this environment.