Most often, the harmonic spectrum for a particular device is given at nameplate load. For PCs and compact fluorescent lamps, the characteristic is fixed and doesn’t vary through time. With variable speed heat pumps and EV battery chargers, there can be quite a bit of variation in the harmonic spectrum as a function of load. Care should be exercised in assigning the appropriate harmonic spectrum to a particular nonlinear load. This is particularly true for monitoring studies since most monitoring equipment computes the harmonic distortion as a function of the fundamental frequency current.
