I am using the VFD for pulverisor application. earlier v were running on auto transormer. at that time during start up it was taking 700amps(75kw) for 3 minuts and then it comes to normal run and was drawing 60amps. now it is running on VFD. now wht happens is during start up it draws normal starting current. but during normal running it is drawing 80 amps. i wanted to know wht could be the problem.

u can write to me on rajnikantsangani@yahoo.co.in

Are u usinga true RMS meter to read the output current.

Hello rajnikantsangani

If the machine is drawing more current than it was when across the line, there are several possible causes.
1. Is the speed the same. If the speed is a little higher, the load wil be higher and so will the current.
2. is the voltage set up correctly. If the voltage profile is set up incorrectly, the voltage could be low and this would increase the current. Check the output voltage setting in the drive, and check voltage profile. You need to have a linear profile, not a square law.
3. How and where are you making the measurement? You need to use an averaging meter, not a peak reading. This means either a moving pointer type meter, or a true RMS digital. A standard digital will often tend to read high.

Best regards