I have a problem with this ACS800-104-0105-3 variable frequency drive model, the output current reading on the VFD is always double the reading of the clamp ampere(i.e. drive reading= 40 A, clamp ampere reading=20 A)
what is the procedure that i can follow to detect the cause of this error?

Mah, I'd check your scaling as the units used are typically 20000 units for full scale, or 10000 units depending upon which memory location/analog output is chosen. ABB provides flexibility in the scaling and many don't recognize that this needs to be reviewed as well as their Max and Min settings. I hope this is a help.

At what frequency are you trying to measure the load? Is your Meter suitable for the application? Usually most VFD metering are more accurate than any external meters. You could test results at different frequencies to get a better idea.

Our general routine measurement meters are designed for power frequency, this will not read the accurate readings. as the output of vfd frequency is variable, so the same is happening. I think so

Mah,
I understand that many clamp meters do not give accurate current readings from the drive due to not being LEM (Hall Effect Devices).
Try using a "fluke meter" and compare the results. I hope this in addition to Bryan & Edmonds advice will help.
Cheers!

I think it sound as a strange problem, when you talk about clamp reading do you then mean the supply reading to the variable frequency drive? and with output reading do you then talk about supply reading to the drive load after the inverter side.
If this is the case then the readings are (ie. 20/40 amps ) !!! wich means that the drive double up the current.
what is the Clamp voltage and the input voltage to the drive. ??

i take some steps:
1- use the clamp ampere in another drive( to measure the output current), the reading of the clamp was the same as the drive reading. so the point of clamp ampere is not the reason of the problem.

second step: i replace the interface card (AINT-14C )of the drive by new one, this card is reasonable of current measurements.but still having the problem.

note: AINT-14C is a ABB code for this card.

I think the problem will be the clamp ampere reading.
If this instrument is not an RMS meter it will not measure the high frequencies of the drive.
(Drive is modulating at about 3kHz)
Drive current measurement is normally very accurate

If you are very very very sure of the clamp reading. (see my last post) then there can be a problem in the settings or firmware of the drive.
Maybe the processorcard (RMIO-XX) has been replaced by another which contains firmware of a different size drive or wrong motor data.
But I do think you are have a measuring fault with the clamp.
Did the other drive have the same modulating type and frequency?