VFD Testing
This method works really well, and is quite green; i.e. low energy: Connect the VFD to a motor, such as a three phase induction motor. The #1 motor is mechanically coupled to an identical three phase motor via a pully/ belt drive, #2 motor. The power connection for motor #2 is the mains, 60 hz supply.. If the VFD frequency speed is such that the slip is negative, i.e. greater than the line frequency, the #2 motor acts as a generator, and will supply energy to the mains. Bear in mind that there are two 'slips' to deal with. #1 motor will look like a conventional load to the VFD, except the net energy lost is one tenth the dynomometer power. I have run two 5 HP motors back to back, and had a net loss of 150 watts at full power.
