Re: Help me to understand concept of motor acceleration by vfd
Usually the acceleration/deceleration ramp time refers to the full scale speed. If you ramp to a smaller speed, e.g. 10 Hz with 50 Hz full scale, the actual ramp time is only 1/5 of the specified time.
It has been clarified that the parameter range has nothing to do with feasible motor acceleration. The VFD drives I'm used to have mostly 0.1 sec resolution for the ramp time, but may even allow 0.0 input. To know the smallest feasible setting, you need to put maximum VFD and motor current and motor moment of inertia in the calculation. Modern VFD sense motor current and rotor speed during spin up and delay the ramp if the motor can't follow it.
The more critical situation is however during ramp down, a too fast deceleration pushes the DC linke voltage and causes an overvoltage fault, unless a brake chopper is installed with the VFD.