April 27th, 2011 
One of the most common misunderstood aspects of applying variable frequency drives (VFD) happens when you retrofit a motor with a drive for the first time. Often the VFD purchased is too small. This happens when a person says, “I have a 10 hp motor so I need a 10 hp drive.”
The problem is that when you start a motor across the line, it has unlimited current from the starter powering it—this current creates the high torque needed to start the motor with its associated load.
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