On 2008-05-18, Bob Engelhardt wrote:
Ignoramus8671 wrote:
The motor has to have a horsepower that the VFD can handle, but any HP
below that is OK.
...

When I was looking for a VFD and researching the ones that came up on
eBay, there was one that said it shouldn't be used on motors of less
than a certain hp. It didn't say why and I'm not saying that it's
always true, just a heads-up that it can be the case that a VFD is too
large for a motor.

Are you sure that wasn't a "Static converter" instead of a VFDj?
Those use a capacitor to produce enough phase shift to start the motor
and then switch it out when the motor is spinning. And if the motor
horsepower is too small, the phase shift won't be right and the motor
will not start. (But you can change the capacitance value to a lower
one to start a smaller motor with it.)

The only way that I could see a true VFD having problems with
too small a motor is if it is monitoring the current in each leg and if
any leg is below a certain limit it might sound an alarm indicating that
it thought that one motor winding had become disconnected.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---