Formula for change in Hz to HP
Formula for change in Hz to HP
(OP)
Hello, I was wondering how the Hz actually effect the hp of a motor using a VFD? For example, lets say I have a 10hp 460v 60hz motor and dropped the hz using a VFD down to 40. How would I calculate the actual hp drop? Thanks you all for your time!





RE: Formula for change in Hz to HP
Reducing frequency from 60 Hz to 40 Hz reduces the shaft power from 10 HP to 10*40/60 = 6.67 HP.
There are details that may influence the outcome but they usually mean less than a few percent and can usually be forgotten.
Gunnar Englund
www.gke.org
RE: Formula for change in Hz to HP
I'm not sure if it was part of your question but above rated speed, the horsepower limit is roughly constant (doesn't increase with speed). That is up until some point in the neighborhood of 150% where ratio of breadown torque over full load torque becomes too low.
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RE: Formula for change in Hz to HP
The base speed is normally that corresponding to the driver maximum voltage output.
RE: Formula for change in Hz to HP