HI
@Jeebs: Yes I see, to both my questions
@bornwild: It will depend on the brand, and what kind of money you want to pay. The VLT2800 is "old" technology, but even then they had the option to put in current transducers in the output. So buy a cheap drive and you'll probably not be able to trust the current reading.
But keep in mind that the theoretical calculation is not a fictional one. It is based on the DC current in the DC-link but influenced by the motor data including the motor magnetization current, and if these data are not correct then the calculation will also be incorrect.
As to your clamp meter, remember that you are meassuring on a current that is NOT a 50 or 60 Hz current. Your meter will be correct at one of those frequencies, but on the switched motor current of a VFD the result will be different. So if I were you I'd still rely on the value from the VFD.
Best regards,
Michal_dk
@Jeebs: Yes I see, to both my questions
@bornwild: It will depend on the brand, and what kind of money you want to pay. The VLT2800 is "old" technology, but even then they had the option to put in current transducers in the output. So buy a cheap drive and you'll probably not be able to trust the current reading.
But keep in mind that the theoretical calculation is not a fictional one. It is based on the DC current in the DC-link but influenced by the motor data including the motor magnetization current, and if these data are not correct then the calculation will also be incorrect.
As to your clamp meter, remember that you are meassuring on a current that is NOT a 50 or 60 Hz current. Your meter will be correct at one of those frequencies, but on the switched motor current of a VFD the result will be different. So if I were you I'd still rely on the value from the VFD.
Best regards,
Michal_dk
