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Vfd Ramp Up Time


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#1 billstrong

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Posted 11 January 2009 - 07:12 AM

Hi,
as we all know VFD changes its frequency gradually from current value to target value(eg. from 30hz to 50hz in 1 second).
my question is how shall we define a suitable time interval from current frequency to target frequency?
if the time interval is not suitalbe what would the result be?
thanks! smile.gif

#2 marke

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Posted 11 January 2009 - 05:57 PM

As the motor is accelerating, it is transferring "acceleration" energy to the load. This is additional energy to the energy required to drive the load.
If you accelerate too quickly, the torque will exceed the capacity for the motor and/or the inverter. Usually, the VFD will have a current or a torque limit to cope with this situation.
The minimum acceleration time is essentially a function of the inertia of the load.

Too slow, is not an issue except for some machines that must get up to speed quickly (i.e. submersible pumps) and it can affect the operation and productivity of the machine.

Best regards,
Mark.




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