I have done some tests to measure the current at the output of a variable frequency drives. Of course you should look at the current that the drive displays, but we had some doubts if the drive was still ok and wanted to compare the current indicated
by the drive with the current measured with a measuring clamp.
I could see that if the motor is running at speed (and not blocked mechanically or at speed 0), the current measured with the clamp is approximately the same as the one indicated by the drive. And this was even with a non true rms clamp.
However if the drive was blocked the current measured with the clamp was completely different from the current indicated by the drive.
Could I conclude that if the drive is running at speed the current measured with a clamp is approximately accurate, and the influence of a true rms or not a true rms clamp will be minimal??
What if the motor is not blocked but running at lower speed then the setpoint (torque reduced), will the measurement then be accurate???
How about measuring at the output of a dc-drive, is a true rms clamp then a real necessity, or will a non true rms clamp also do the job (like for the vfd).
Share me your experiences in measuring current with a measuring clamp.
Thanks.
by the drive with the current measured with a measuring clamp.
I could see that if the motor is running at speed (and not blocked mechanically or at speed 0), the current measured with the clamp is approximately the same as the one indicated by the drive. And this was even with a non true rms clamp.
However if the drive was blocked the current measured with the clamp was completely different from the current indicated by the drive.
Could I conclude that if the drive is running at speed the current measured with a clamp is approximately accurate, and the influence of a true rms or not a true rms clamp will be minimal??
What if the motor is not blocked but running at lower speed then the setpoint (torque reduced), will the measurement then be accurate???
How about measuring at the output of a dc-drive, is a true rms clamp then a real necessity, or will a non true rms clamp also do the job (like for the vfd).
Share me your experiences in measuring current with a measuring clamp.
Thanks.