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Calculating energy consumption, 3 phase

Calculating energy consumption, 3 phase

Calculating energy consumption, 3 phase

(OP)
Bright idea:  Replacing pulleys on an AHU w/VFD.  AHU normally runs at 67%, so I thought adjusting the ratio of drive to driven to put the motor closer to it's more efficient speed.  Ok, increased the drive to driven by 20%.  Motor speed is up to 76% (didn't go quite as far as I had hoped), current draw is down from 12.5 to 10.6 amps at 492v (Nice!  Down 18%).  I know how to calculate single phase energy consumption (amps to watts), but am not sure if there's a trick to calculating 3 phase.  Any takers here?  I understand Ohm's law isn't hard and fast on motors, I'm just looking for somewhere of a ballpark estimate of reduction in wattage.  --Ray

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