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I want to power and control the RPM of three 115v .47amp shaded pole axial fans each powered by a separate leg of the 3-phase coming from a VFD. Can it be done? I'd like them to run at full speed (60hz) down to possibly half of that or less if that's an option.

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  • \$\begingroup\$ Two legs, not one \$\endgroup\$ – Gregory Kornblum Jan 15 '18 at 19:42
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Most VFDs have a mode of control that is not senseless vector. That mode is often called the "V/Hz" mode. If you select that mode, it should be possible to power three shaded pole motors driving fan loads. Some VFDs may have a "load loss" or "load imbalance" protection feature, but I don't think that either of those features is common. VFDs usually have sufficient configuration adjustment ranges to allow setting up for 115V output at 60 Hz.

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Given any reasonable VFD has a current regulation, no.

  • Reactive currents in the individual legs will differ depending on speed.
  • Active currents in the individual legs will differ depending on the load situation.

This will make the VFD go into failure mode, expecting the single motor it was designed for to be broken.

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