I am developing a PQM system for a three-phase voltage with three more wires (neutral - ground) to the outputs of a VFD. The voltage and current values reach almost zero when the VFD is turned off (as it should be), but the frequency value begins to be read at a value close to 60 Hz, if the lines are disconnected by means of a contactor and measures 180 Hz with the lines connected but with the VFD output at zero.
When restarting the ADE7880 the first reading goes to 0, but then the following measurements are 60 Hz or 180 Hz, depending on whether I have the lines open or closed through the main contactor.
Someone could tell me why this is due.
Is the contactor disconnecting the VFD completely ?(phases,neutral)
What registers are you reading for you freq/period measurement that is changing ?
Since you are using a VFD do you expect to do harmonic measurement at a fundamental other than 50 or 60 HZ.
Thanks for answering Dave. The problem is not noise, because I short-circuit the 4 voltage inputs of the ADE7880 to the analog ground and although the voltage goes to zero, the frequency always read it60 Hz when when the contactor is open and 180 Hz, when the contactor is closed, but without voltage output from the VFD.But only the 30 Hz super drive at its output, the PERIOD registers show the VFD output frequency, but the idea is that in the absence of VFD output the records are loaded with 000000